- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41252] EP 251220a: COLIBRÍ detection of the optical counterpart
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43167 SUBJECT: EP 251220a: COLIBRÍ detection of the optical counterpart DATE: 25/12/21 05:53:22 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Fredd Sánchez Álvarez (UNAM), Ny Avo Rakotondrainibe (LAM), Leonardo García García (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Jean-Grégoire Ducoin (CPPM), Enrique Moreno Méndez (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM). We imaged the field of the fast X-ray transient EP251220a (Liu et al., GCN Circ. 43162) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-21 04:08 UTC to 04:35 UTC (from 19.70 to 20.13 hr after the trigger) and obtained 18 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analyzed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we detect an uncataloged source at the FXT uncertainty region (Liu et al., GCN Circ. 43162) at RA (J2000) = 01:09:16.60 = 17.31915 deg Dec (J2000) = +19:05:32.3 = 19.09231 deg with an uncertainty of about 0.5 arcsec and with preliminary magnitudes of r = 21.15 +/- 0.02 z = 20.72 +/- 0.04 We suggest that this is the counterpart of the fast X-ray transient. Further observations will be necessary to detect fading. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43167. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41251] GRB 251221A: Swift detection of a burst
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43166 SUBJECT: GRB 251221A: Swift detection of a burst DATE: 25/12/21 05:38:42 GMT FROM: Elena Ambrosi at INAF-IASF <elena.ambrosi(a)inaf.it> E. Ambrosi (INAF-IASFPA), C. Gronwall (PSU), R. Gupta (NASA GSFC), A. Melandri (INAF-OAR), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 05:24:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251221A (trigger=1426088). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 101.408, +0.729 which is RA(J2000) = 06h 45m 38s Dec(J2000) = +00d 43' 45" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 50 sec. The peak count rate was ~1300 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 05:26:50.3 UT, 138.4 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 101.42801, 0.73241 which is equivalent to: RA(J2000) = 06h 45m 42.72s Dec(J2000) = +00d 43' 56.7" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 73 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 7.34 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 142 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain, extinction expected. Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43166. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41250] Swift GRB251221.23: Global MASTER-Net observations report
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43165 SUBJECT: Swift GRB251221.23: Global MASTER-Net observations report DATE: 25/12/21 05:36:25 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB251221.23 (trigger No 1426088,06h 45m 37.92s , +00d 43m 44.4s, R=0.05) errorbox 19 sec after notice time and 67 sec after trigger time at 2025-12-21 05:25:39 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 32 deg. The sun altitude is -34.1 deg. The galactic latitude b = -0 deg., longitude l = 212 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3079192 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 72 | MASTER-OAFA | C | 10 | 18.2 | 95 | MASTER-OAFA | C | 20 | 17.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43165. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41249] GRB 251221A: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43164 SUBJECT: GRB 251221A: Fermi GBM Final Real-time Localization DATE: 25/12/21 05:35:02 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 05:24:28 UT on 21 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251221A (trigger 787987473.613216 / 251221225). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 96.6, Dec = 1.6 (J2000 degrees, equivalent to J2000 06h 26m, 1d 36'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 100.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251221225/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251221225/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251221225/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43164. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41248] EP251220a: Global MASTER-Net observations report
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43163 SUBJECT: EP251220a: Global MASTER-Net observations report DATE: 25/12/21 05:09:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251220a ( EP Team et al., GCN 43162) errorbox 23634 sec after trigger time at 2025-12-20 15:00:37 UT, with upper limit up to 17.9 mag. Observations started at twilight. The observations began at zenith distance = 28 deg. The sun altitude is -14.4 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251220a errorbox 70921 sec after trigger time at 2025-12-21 04:08:44 UT, with upper limit up to 16.1 mag. The observations began at zenith distance = 81 deg. The sun altitude is -35.3 deg. The galactic latitude b = -43 deg., longitude l = 130 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3079135 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 23665 | 2025-12-20 15:00:37 | MASTER-Kislovodsk | (01h 06m 41.00s , +20d 06m 46.9s) | C | 60 | 14.1 | 24358 | 2025-12-20 15:12:11 | MASTER-Kislovodsk | (01h 13m 48.06s , +18d 34m 54.1s) | C | 60 | 17.8 | 24438 | 2025-12-20 15:13:31 | MASTER-Kislovodsk | (01h 14m 45.05s , +20d 30m 16.8s) | C | 60 | 17.7 | 24598 | 2025-12-20 15:16:11 | MASTER-Kislovodsk | (01h 01m 10.07s , +18d 35m 48.4s) | C | 60 | 17.9 | 24598 | 2025-12-20 15:16:11 | MASTER-Kislovodsk | (01h 05m 50.48s , +18d 12m 44.0s) | C | 60 | 14.2 | 70952 | 2025-12-21 04:08:44 | MASTER-OAFA | (01h 09m 37.27s , +19d 10m 42.5s) | C | 60 | 16.1 | 71017 | 2025-12-21 04:09:50 | MASTER-OAFA | (01h 09m 37.22s , +19d 10m 42.5s) | C | 60 | 15.9 | 71083 | 2025-12-21 04:10:56 | MASTER-OAFA | (01h 09m 37.31s , +19d 10m 39.9s) | C | 60 | 15.9 | 71159 | 2025-12-21 04:12:11 | MASTER-OAFA | (01h 09m 37.27s , +19d 10m 38.5s) | C | 60 | 15.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43163. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41247] EP251220a: Global MASTER-Net observations report
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43163 SUBJECT: EP251220a: Global MASTER-Net observations report DATE: 25/12/21 05:09:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251220a ( EP Team et al., GCN 43162) errorbox 23634 sec after trigger time at 2025-12-20 15:00:37 UT, with upper limit up to 17.9 mag. Observations started at twilight. The observations began at zenith distance = 28 deg. The sun altitude is -14.4 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251220a errorbox 70921 sec after trigger time at 2025-12-21 04:08:44 UT, with upper limit up to 16.1 mag. The observations began at zenith distance = 81 deg. The sun altitude is -35.3 deg. The galactic latitude b = -43 deg., longitude l = 130 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3079135 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 23665 | 2025-12-20 15:00:37 | MASTER-Kislovodsk | (01h 06m 41.00s , +20d 06m 46.9s) | C | 60 | 14.1 | 24358 | 2025-12-20 15:12:11 | MASTER-Kislovodsk | (01h 13m 48.06s , +18d 34m 54.1s) | C | 60 | 17.8 | 24438 | 2025-12-20 15:13:31 | MASTER-Kislovodsk | (01h 14m 45.05s , +20d 30m 16.8s) | C | 60 | 17.7 | 24598 | 2025-12-20 15:16:11 | MASTER-Kislovodsk | (01h 01m 10.07s , +18d 35m 48.4s) | C | 60 | 17.9 | 24598 | 2025-12-20 15:16:11 | MASTER-Kislovodsk | (01h 05m 50.48s , +18d 12m 44.0s) | C | 60 | 14.2 | 70952 | 2025-12-21 04:08:44 | MASTER-OAFA | (01h 09m 37.27s , +19d 10m 42.5s) | C | 60 | 16.1 | 71017 | 2025-12-21 04:09:50 | MASTER-OAFA | (01h 09m 37.22s , +19d 10m 42.5s) | C | 60 | 15.9 | 71083 | 2025-12-21 04:10:56 | MASTER-OAFA | (01h 09m 37.31s , +19d 10m 39.9s) | C | 60 | 15.9 | 71159 | 2025-12-21 04:12:11 | MASTER-OAFA | (01h 09m 37.27s , +19d 10m 38.5s) | C | 60 | 15.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43163. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41246] EP251220a: EP detection of a fast X-ray transient
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43162 SUBJECT: EP251220a: EP detection of a fast X-ray transient DATE: 25/12/21 04:44:20 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Liu (THU), Y. Wang (PMO), H. Y. Liu, H. W. Pan (NAO,CAS) on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient, designated EP251220a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-12-20T08:26:43 (UTC). The position of the source is R.A. =17.322 deg, DEC = 19.080 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for nearly 170 seconds. The transient did not trigger the WXT onboard unit. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 2.2 (+1.5/-1.1) with a column density of 0.2 (+0.4/-0.2) x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 1.2 (+1.2/-0.4) x 10^-9 erg/s/cm^2. The peak flux is around 4.4 x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The Follow-up X-ray Telescope (FXT) on board the EP performed a ToO observation for EP251220a, starting at 2025-12-21T03:16:08 (UTC). Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 17.3160 deg, DEC = 19.0935 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43162. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41245] SVOM GRB251220.98: Global MASTER-Net observations report
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43161 SUBJECT: SVOM GRB251220.98: Global MASTER-Net observations report DATE: 25/12/21 00:56:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the SVOM GRB251220.98 (trigger No 1766273885,18h 57m 31.51s , +68d 19m 14.2s, R=1) errorbox 616 sec after notice time and 649 sec after trigger time at 2025-12-20 23:48:54 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 67 deg. The sun altitude is -51.7 deg. The galactic latitude b = 25 deg., longitude l = 99 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3078836 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 740 | 2025-12-20 23:48:54 | MASTER-Kislovodsk | (18h 56m 08.59s , +68d 09m 08.0s) | C | 180 | 18.2 | 740 | 2025-12-20 23:48:54 | MASTER-Kislovodsk | (19h 06m 49.88s , +67d 44m 25.1s) | C | 180 | 14.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43161. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41244] GRB 251220B: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43160 SUBJECT: GRB 251220B: Fermi GBM Final Real-time Localization DATE: 25/12/20 23:48:38 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 23:38:04 UT on 20 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251220B (trigger 787966689.62881 / 251220985). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 251.4, Dec = 47.9 (J2000 degrees, equivalent to J2000 16h 45m, 47d 53'), with a statistical uncertainty of 6.4 degrees. The angle from the Fermi LAT boresight is 40.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251220985/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43160. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41243] GRB 251219A: SVOM/GRM observation of a short burst
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43159 SUBJECT: GRB 251219A: SVOM/GRM observation of a short burst DATE: 25/12/20 17:45:55 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short soft GRB 251219A (SVOM trigger reference: sb25121902) at 2025-12-19T02:36:31.600 UTC (T0), which is also detected by GECAM-B (Wang et al., GCN#43158). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 0.16 +0.12/-0.02 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251219A.png In addition, the position of this burst, as determined by GECAM-B (RA= 296.5, DEC= -11.9, ERR=5.6), is located at about 126 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43159. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41242] GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43158 SUBJECT: GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645 DATE: 25/12/20 17:41:34 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a short soft burst GRB 251219A, at 2025-12-19T02:36:31.550 UTC (denoted as T0), which is also detected by SVOM/GRM. According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.22 +0.08/-0.16 s. The signal is mainly detected in energy lower than 200 keV. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251219A.png GECAM-B localized this burst to the following position (J2000): Ra: 274.4 deg Dec: -4.8 deg Err: 4.3 deg (1-sigma, statistical only) We note that the localization is consistent with the magnetar SGR 1830-0645. The short duration and soft spectrum also suggest this is a magnetar X-ray burst. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43158. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41241] Fermi-LAT Gamma-ray Observations of IceCube-251218A
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43157 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251218A DATE: 25/12/20 15:25:16 GMT FROM: chiara.bartolini-1(a)unitn.it C. Bartolini (Univ. of Trento and INFN Bari), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC251218A neutrino event (GCN 43151) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-12-18 at 20:21:00.63 UTC (T0) with J2000 position RA = 353.60 (+0.90, -0.74) deg, Decl. = 44.15 (+0.46, -0.45) deg 90% PSF containment (J2000). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC251218A localization region (4FGL-DR4, The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). This is the unassociated gamma-ray source 4FGL J2331.6+4430. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month prior to T0, this object is not significantly detected (> 5 sigma). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC251218A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251218A best-fit position, the >100 MeV flux upper limit (95% confidence) is <9.6e-11 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <9.2e-09 (<8.8e-08) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is C. Bartolini (chiara.bartolini at ba.infn.it). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43157. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41240] GRB 251220A: MAXI/GSC detection
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43156 SUBJECT: GRB 251220A: MAXI/GSC detection DATE: 25/12/20 12:17:45 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> M. Uenishi (Ehime U.), H. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), and S. Yamada (Tohoku U) The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source at 10:37:16 UT on December 20, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (19.609 deg, -15.607 deg) = (01 18 26, -15 36 25) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.38 deg and 0.28 deg, respectively. The roll angle of long axis from the north direction is 173.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 104 +- 23 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (18.401, -15.400) deg = (01 13 36, -15 24 00) (J2000) (R.A., Dec) = (18.492, -16.164) deg = (01 13 58, -16 09 50) (J2000) (R.A., Dec) = (21.034, -15.868) deg = (01 24 08, -15 52 04) (J2000) (R.A., Dec) = (20.934, -15.105) deg = (01 23 44, -15 06 18) (J2000) There was no significant excess flux in the previous transit at 09:04 UT and in the next transit at 12:10 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/43156. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41239] GRB 251215A: Swift-XRT afterglow detection
by GCN Circulars 20 Dec '25

20 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43155 SUBJECT: GRB 251215A: Swift-XRT afterglow detection DATE: 25/12/20 11:59:19 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Swift/BAT-detected burst GRB 251215A. The observations now extend from T0+32.0 ks to T0+383.9 ks and have a total exposure time of 9.9 ks. Of the sources previously reported, "Source 5" is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1629 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 122.61893, -36.74266 which is equivalent to: RA (J2000): 08h 10m 28.54s Dec(J2000): -36d 44' 33.6" with an uncertainty of 5.7 arcsec (radius, 90% confidence). This position is 97 arcsec from the Swift/BAT position. The source is fading with alpha >0.3. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021894/Source5.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021894. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43155. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41238] IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43154 SUBJECT: IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/12/19 20:55:41 GMT FROM: Alicia Mand at IceCube/UW-Madison <aemand(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-251218A (https://gcn.nasa.gov/circulars/43151) in a time range of 1000 seconds centered on the alert event time (2025-12-18 20:12:40.630 UTC to 2025-12-18 20:29:20.630 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-251218A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251218A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 5e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-12-17 20:21:00.630 UTC to 2025-12-19 20:21:00.630 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.8e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251218A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/43154. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41237] IceCube-251218A: COLIBRÍ optical upper limits
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43153 SUBJECT: IceCube-251218A: COLIBRÍ optical upper limits DATE: 25/12/19 08:35:20 GMT FROM: antier(a)ijclab.in2p3.fr Sarah Antier (IJCLAB), Enrique Moreno Méndez (UNAM), Noémie Globus (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We observed the field of the IceCube-251218A (GCN 43151) (bronzetrack) event with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We observed four pointings centred on (RA, Dec) = (353.8851, 44.3568), (353.3414, 44.3590), (353.8784, 43.9697), and (353.3374, 43.9697) between 2025-12-19 02:26 UTC and 03:10 UTC (from 6.09 to 6.59 hours after the trigger). At each pointing we obtained 8 minutes of simultaneous exposure in r and z over a field of 26 x 26 arcmin. These pointings cover a region of approximately 1 x 1 degree centered on (RA, Dec) = (353.60, 44.15) and cover most of the 90% uncertainty region. The data were coadded with the COLIBRÍ ASU pipeline and analysed in STDWeb/STDPipe (Karpov 2025). Comparing our observations (and after performing image subtraction) against Pan-STARRS DR1, we detect no evident uncatalogued sources within the observed fields to a 10-sigma limiting AB magnitudes of: r > 21.9 and z > 20.8 These values are not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43153. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41236] SVOM GRB251219.11: Global MASTER-Net observations report
by GCN Circulars 19 Dec '25

19 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43152 SUBJECT: SVOM GRB251219.11: Global MASTER-Net observations report DATE: 25/12/19 02:56:55 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the SVOM GRB251219.11 (trigger No 1766111792,04h 46m 20.50s , -33d 01m 10.2s, R=1) errorbox 29 sec after notice time and 58 sec after trigger time at 2025-12-19 02:37:29 UT, with upper limit up to 20.2 mag. The observations began at zenith distance = 12 deg. The sun altitude is -29.1 deg. The galactic latitude b = -39 deg., longitude l = 235 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3076431 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 63 | 2025-12-19 02:37:29 | MASTER-OAFA | (04h 46m 42.87s , -33d 06m 20.3s) | C | 10 | 19.2 | 81 | 2025-12-19 02:37:47 | MASTER-OAFA | (04h 46m 42.91s , -33d 06m 20.5s) | C | 10 | 19.2 | 104 | 2025-12-19 02:38:05 | MASTER-OAFA | (04h 46m 42.96s , -33d 06m 20.4s) | C | 20 | 19.7 | 131 | 2025-12-19 02:38:32 | MASTER-OAFA | (04h 46m 43.03s , -33d 06m 20.2s) | C | 20 | 19.8 | 184 | 2025-12-19 02:39:20 | MASTER-OAFA | (04h 46m 43.11s , -33d 06m 19.5s) | C | 30 | 18.4 | 227 | 2025-12-19 02:39:58 | MASTER-OAFA | (04h 46m 43.21s , -33d 06m 19.3s) | C | 40 | 20.1 | 278 | 2025-12-19 02:40:44 | MASTER-OAFA | (04h 46m 43.31s , -33d 06m 18.8s) | C | 50 | 20.2 | 340 | 2025-12-19 02:41:41 | MASTER-OAFA | (04h 46m 43.43s , -33d 06m 18.1s) | C | 60 | 20.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41235] IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43151 SUBJECT: IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/12/18 21:55:53 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-12-18 at 20:21:00.63 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 0.8234 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141741_9008919.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-12-18 Time: 20:21:00.63 UT RA: 353.60 (+0.90/-0.74 deg 90% PSF containment) J2000 Dec: 44.15 (+0.46/-0.45 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. There is one Fermi 4FGL-DR4 source in the 90% uncertainty region, i.e., the unassociated gamma-ray source 4FGL J2331.6+4430 at RA: 552.90 deg, Dec: 44.51 deg J2000 (0.62 deg away from the best-fit event position). The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/43151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41234] IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43151 SUBJECT: IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/12/18 21:55:53 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-12-18 at 20:21:00.63 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 0.8234 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141741_9008919.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-12-18 Time: 20:21:00.63 UT RA: 353.60 (+0.90/-0.74 deg 90% PSF containment) J2000 Dec: 44.15 (+0.46/-0.45 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. There is one Fermi 4FGL-DR4 source in the 90% uncertainty region, i.e., the unassociated gamma-ray source 4FGL J2331.6+4430 at RA: 552.90 deg, Dec: 44.51 deg J2000 (0.62 deg away from the best-fit event position). The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/43151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41233] IceCube Alert 251218.85: Global MASTER-Net observations report
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43150 SUBJECT: IceCube Alert 251218.85: Global MASTER-Net observations report DATE: 25/12/18 20:39:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the IceCube Alert 251218.85 (trigger No 9008919,23h 34m 08.64s , +44d 08m 42.0s, R=0.51) errorbox 64 sec after notice time and 107 sec after trigger time at 2025-12-18 20:22:48 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 57 deg. The sun altitude is -68.4 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the IceCube Alert 251218.85 errorbox 247 sec after notice time and 290 sec after trigger time at 2025-12-18 20:25:51 UT, with upper limit up to 18.0 mag. The observations began at zenith distance = 80 deg. The sun altitude is -42.5 deg. The galactic latitude b = -16 deg., longitude l = 109 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3076097 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 117 | 2025-12-18 20:22:48 | MASTER-Kislovodsk | (23h 32m 34.10s , +44d 07m 24.4s) | P- | 20 | 16.8 | 117 | 2025-12-18 20:22:48 | MASTER-Kislovodsk | (23h 32m 25.71s , +44d 29m 51.7s) | P| | 20 | 16.9 | 162 | 2025-12-18 20:23:28 | MASTER-Kislovodsk | (23h 32m 33.96s , +44d 07m 21.9s) | P- | 30 | 17.0 | 321 | 2025-12-18 20:25:51 | MASTER-Tunka | (23h 34m 38.20s , +44d 21m 36.4s) | C | 60 | 18.0 | 321 | 2025-12-18 20:25:51 | MASTER-Tunka | (23h 34m 16.79s , +44d 26m 39.9s) | C | 60 | 17.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43150. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41232] GRB 251214B: VIRT Optical Upper Limit
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43149 SUBJECT: GRB 251214B: VIRT Optical Upper Limit DATE: 25/12/18 16:23:01 GMT FROM: Priya Gokuldass at ERAU <gokuldap(a)my.erau.edu> P. Gokuldass (ERAU), F. George (UVI), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), and T. Lombardi (Eckerd College) report: We observed the field of long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112), and GECAM-B (Luo et al., GCN 43113) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-12-14 starting at 23:12:24.856 UTC (T-mid ~ T0 + ~15h). We performed a series of exposures in an R filter with a total exposure of 1210s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 2.06. We do not detect any source at the enhanced XRT position reported (Evans et al., GCN 43098). This non-detection is consistent with reported detections (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123, de Ugarte Postigo et al., GCN 43131) and upper limits (Volnova et al., GCN 43124; Pankov et al., GCN 43132; Volnova et al., GCN 43141; Lin et al., GCN 43134). We report the following 3-sigma upper limit: T_mid ||Exposure ||Filter ||Limit T+ ~15h || 1210s || R || > 20.4 The limit is estimated from comparison to nearby Gaia D3 synphot stars and is not corrected for Galactic extinction. We acknowledge the use of STDWeb interface to verify our result. We acknowledge financial support in part from NASA EPSCoR 80NNSC22M0063, NSF AST 2319415, and NASA EPSCoR 80NSSC24M0112. This message can be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43149. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41231] Fermi trigger No 787736968: Global MASTER-Net observations report
by GCN Circulars 18 Dec '25

18 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43148 SUBJECT: Fermi trigger No 787736968: Global MASTER-Net observations report DATE: 25/12/18 12:30:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB251218.33 (trigger No 787736968,01h 20m 19.20s , +08d 31m 12.0s, R=2) errorbox 12771 sec after notice time and 12805 sec after trigger time at 2025-12-18 11:22:48 UT, with upper limit up to 15.0 mag. The observations began at zenith distance = 44 deg. The sun altitude is -21.0 deg. The galactic latitude b = -53 deg., longitude l = 136 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3075501 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12835 | 2025-12-18 11:22:48 | MASTER-Tunka | (01h 32m 31.99s , +10d 56m 59.4s) | C | 60 | 15.0 | 12835 | 2025-12-18 11:22:48 | MASTER-Tunka | (01h 32m 06.93s , +11d 03m 54.2s) | C | 60 | 14.7 | 13495 | 2025-12-18 11:33:47 | MASTER-Tunka | (01h 16m 38.29s , +09d 03m 21.8s) | C | 60 | 14.6 | 13495 | 2025-12-18 11:33:47 | MASTER-Tunka | (01h 16m 13.08s , +09d 10m 03.4s) | C | 60 | 14.5 | 15014 | 2025-12-18 11:59:06 | MASTER-Tunka | (01h 31m 58.57s , +09d 01m 47.3s) | C | 60 | 13.3 | 15014 | 2025-12-18 11:59:06 | MASTER-Tunka | (01h 31m 32.75s , +09d 08m 12.9s) | C | 60 | 13.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43148. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41230] Fermi GRB 251217A: Global MASTER-Net observations report
by GCN Circulars 17 Dec '25

17 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43147 SUBJECT: Fermi GRB 251217A: Global MASTER-Net observations report DATE: 25/12/17 10:30:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251217A ( Fermi GBM team, GCN 43146) errorbox 20114 sec after notice time and 20149 sec after trigger time at 2025-12-17 10:11:24 UT, with upper limit up to 15.0 mag. Observations started at twilight. The observations began at zenith distance = 34 deg. The sun altitude is -10.4 deg. The galactic latitude b = -24 deg., longitude l = 75 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3074063 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 20179 | 2025-12-17 10:11:24 | MASTER-Tunka | (21h 35m 28.03s , +20d 25m 27.5s) | C | 60 | 13.1 | 20179 | 2025-12-17 10:11:24 | MASTER-Tunka | (21h 34m 58.00s , +20d 33m 14.0s) | C | 60 | 13.2 | Coadd 20292 | 2025-12-17 10:13:16 | MASTER-Tunka | (21h 51m 44.22s , +20d 24m 29.5s) | C | 60 | 13.4 | 20292 | 2025-12-17 10:13:16 | MASTER-Tunka | (21h 51m 14.04s , +20d 32m 16.2s) | C | 60 | 13.3 | Coadd 20380 | 2025-12-17 10:14:44 | MASTER-Tunka | (21h 35m 47.63s , +22d 17m 22.2s) | C | 60 | 14.0 | 20380 | 2025-12-17 10:14:44 | MASTER-Tunka | (21h 35m 16.43s , +22d 25m 10.6s) | C | 60 | 13.9 | Coadd 20471 | 2025-12-17 10:16:15 | MASTER-Tunka | (21h 52m 15.88s , +22d 17m 38.4s) | C | 60 | 14.4 | 20471 | 2025-12-17 10:16:15 | MASTER-Tunka | (21h 51m 44.47s , +22d 25m 28.7s) | C | 60 | 14.1 | Coadd 20551 | 2025-12-17 10:17:35 | MASTER-Tunka | (21h 36m 35.83s , +18d 30m 47.9s) | C | 60 | 14.1 | 20551 | 2025-12-17 10:17:35 | MASTER-Tunka | (21h 36m 06.57s , +18d 38m 25.9s) | C | 60 | 14.0 | Coadd 20627 | 2025-12-17 10:18:52 | MASTER-Tunka | (21h 37m 36.82s , +24d 11m 25.5s) | C | 60 | 14.7 | 20627 | 2025-12-17 10:18:52 | MASTER-Tunka | (21h 37m 04.28s , +24d 19m 15.4s) | C | 60 | 14.7 | Coadd 20696 | 2025-12-17 10:20:01 | MASTER-Tunka | (21h 52m 37.33s , +18d 31m 07.7s) | C | 60 | 14.3 | 20697 | 2025-12-17 10:20:01 | MASTER-Tunka | (21h 52m 07.99s , +18d 38m 46.5s) | C | 60 | 14.4 | Coadd 20780 | 2025-12-17 10:21:25 | MASTER-Tunka | (21h 54m 10.78s , +24d 12m 19.4s) | C | 60 | 15.0 | 20780 | 2025-12-17 10:21:25 | MASTER-Tunka | (21h 53m 38.02s , +24d 20m 11.0s) | C | 60 | 14.8 | Coadd 20859 | 2025-12-17 10:22:43 | MASTER-Tunka | (21h 39m 01.33s , +16d 37m 07.5s) | C | 60 | 14.1 | 20859 | 2025-12-17 10:22:43 | MASTER-Tunka | (21h 38m 33.01s , +16d 44m 37.9s) | C | 60 | 14.1 | Coadd 20904 | 2025-12-17 10:23:29 | MASTER-Tunka | (21h 40m 56.75s , +26d 06m 13.6s) | C | 60 | 14.7 | 20904 | 2025-12-17 10:23:29 | MASTER-Tunka | (21h 40m 22.72s , +26d 14m 06.3s) | C | 60 | 14.8 | 20978 | 2025-12-17 10:24:42 | MASTER-Tunka | (21h 54m 49.93s , +16d 35m 09.2s) | C | 60 | 13.9 | 20978 | 2025-12-17 10:24:42 | MASTER-Tunka | (21h 54m 21.45s , +16d 42m 40.1s) | C | 60 | 13.9 | 21053 | 2025-12-17 10:25:57 | MASTER-Tunka | (21h 18m 53.52s , +20d 30m 39.4s) | C | 60 | 14.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43147. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41229] Fermi GRB 251217A: Global MASTER-Net observations report
by GCN Circulars 17 Dec '25

17 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43147 SUBJECT: Fermi GRB 251217A: Global MASTER-Net observations report DATE: 25/12/17 10:30:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251217A ( Fermi GBM team, GCN 43146) errorbox 20114 sec after notice time and 20149 sec after trigger time at 2025-12-17 10:11:24 UT, with upper limit up to 15.0 mag. Observations started at twilight. The observations began at zenith distance = 34 deg. The sun altitude is -10.4 deg. The galactic latitude b = -24 deg., longitude l = 75 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3074063 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 20179 | 2025-12-17 10:11:24 | MASTER-Tunka | (21h 35m 28.03s , +20d 25m 27.5s) | C | 60 | 13.1 | 20179 | 2025-12-17 10:11:24 | MASTER-Tunka | (21h 34m 58.00s , +20d 33m 14.0s) | C | 60 | 13.2 | Coadd 20292 | 2025-12-17 10:13:16 | MASTER-Tunka | (21h 51m 44.22s , +20d 24m 29.5s) | C | 60 | 13.4 | 20292 | 2025-12-17 10:13:16 | MASTER-Tunka | (21h 51m 14.04s , +20d 32m 16.2s) | C | 60 | 13.3 | Coadd 20380 | 2025-12-17 10:14:44 | MASTER-Tunka | (21h 35m 47.63s , +22d 17m 22.2s) | C | 60 | 14.0 | 20380 | 2025-12-17 10:14:44 | MASTER-Tunka | (21h 35m 16.43s , +22d 25m 10.6s) | C | 60 | 13.9 | Coadd 20471 | 2025-12-17 10:16:15 | MASTER-Tunka | (21h 52m 15.88s , +22d 17m 38.4s) | C | 60 | 14.4 | 20471 | 2025-12-17 10:16:15 | MASTER-Tunka | (21h 51m 44.47s , +22d 25m 28.7s) | C | 60 | 14.1 | Coadd 20551 | 2025-12-17 10:17:35 | MASTER-Tunka | (21h 36m 35.83s , +18d 30m 47.9s) | C | 60 | 14.1 | 20551 | 2025-12-17 10:17:35 | MASTER-Tunka | (21h 36m 06.57s , +18d 38m 25.9s) | C | 60 | 14.0 | Coadd 20627 | 2025-12-17 10:18:52 | MASTER-Tunka | (21h 37m 36.82s , +24d 11m 25.5s) | C | 60 | 14.7 | 20627 | 2025-12-17 10:18:52 | MASTER-Tunka | (21h 37m 04.28s , +24d 19m 15.4s) | C | 60 | 14.7 | Coadd 20696 | 2025-12-17 10:20:01 | MASTER-Tunka | (21h 52m 37.33s , +18d 31m 07.7s) | C | 60 | 14.3 | 20697 | 2025-12-17 10:20:01 | MASTER-Tunka | (21h 52m 07.99s , +18d 38m 46.5s) | C | 60 | 14.4 | Coadd 20780 | 2025-12-17 10:21:25 | MASTER-Tunka | (21h 54m 10.78s , +24d 12m 19.4s) | C | 60 | 15.0 | 20780 | 2025-12-17 10:21:25 | MASTER-Tunka | (21h 53m 38.02s , +24d 20m 11.0s) | C | 60 | 14.8 | Coadd 20859 | 2025-12-17 10:22:43 | MASTER-Tunka | (21h 39m 01.33s , +16d 37m 07.5s) | C | 60 | 14.1 | 20859 | 2025-12-17 10:22:43 | MASTER-Tunka | (21h 38m 33.01s , +16d 44m 37.9s) | C | 60 | 14.1 | Coadd 20904 | 2025-12-17 10:23:29 | MASTER-Tunka | (21h 40m 56.75s , +26d 06m 13.6s) | C | 60 | 14.7 | 20904 | 2025-12-17 10:23:29 | MASTER-Tunka | (21h 40m 22.72s , +26d 14m 06.3s) | C | 60 | 14.8 | 20978 | 2025-12-17 10:24:42 | MASTER-Tunka | (21h 54m 49.93s , +16d 35m 09.2s) | C | 60 | 13.9 | 20978 | 2025-12-17 10:24:42 | MASTER-Tunka | (21h 54m 21.45s , +16d 42m 40.1s) | C | 60 | 13.9 | 21053 | 2025-12-17 10:25:57 | MASTER-Tunka | (21h 18m 53.52s , +20d 30m 39.4s) | C | 60 | 14.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43147. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41228] GRB 251217A: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Dec '25

17 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43146 SUBJECT: GRB 251217A: Fermi GBM Final Real-time Localization DATE: 25/12/17 04:46:13 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 04:35:34 UT on 17 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251217A (trigger 787638939.89203 / 251217191). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 325.8, Dec = 20.9 (J2000 degrees, equivalent to J2000 21h 43m, 20d 53'), with a statistical uncertainty of 6.6 degrees. The angle from the Fermi LAT boresight is 29.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251217191/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251217191/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251217191/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43146. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41227] GRB 251215A: Swift/UVOT Upper LImits
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43145 SUBJECT: GRB 251215A: Swift/UVOT Upper LImits DATE: 25/12/16 18:52:06 GMT FROM: S. R. Oates at Lancaster University <samantha.oates(a)ucl.ac.uk> S. R. Oates (Lancaster U.) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251215A 32 ks after the Fermi/GBM trigger (Fermi GBM team, GCN Circ. 43104). No optical afterglow is found in the initial UVOT exposures. The UVOT exposures include the positions of XRT sources 2, 5, 6 and 8 (Osborne et al., GCN 43137). The positions of XRT sources 2, 6, and 8 are consistent with known USNO-B1 sources. No optical source is found consistent with XRT source 5. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL white 31995 49531 4297 >22.4 The magnitudes in the table are not corrected for the Galactic extinction due to the significant reddening of E(B-V) = 0.87 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43145. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41226] GRB 251215A: Fermi GBM Observation
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43144 SUBJECT: GRB 251215A: Fermi GBM Observation DATE: 25/12/16 18:31:35 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 04:21:21.57 UT on 15 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251215A (trigger 787465286/251215181), which was also detected by Swift-BAT-GUANO (Ronchini et al. 2025, GCN 43114), Swift-XRT (Osborne et al. 2025, GCN 43137) and Glowbug (Cheung et al. 2025, GCN 43133). The real-time Fermi GBM location (GCN 43104) is consistent with the Swift-BAT position. The GBM light curve consists of multiple overlapping pulses with a duration (T90) of about 143 s (50-300 keV). The time-averaged spectrum from T0-37 to T0+162 s is best fit by a Band function with Epeak = 35 +/- 7 keV, alpha = -1 +/- 0.3, and beta = -1.97 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (2.05 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+64 s in the 10-1000 keV band is 5.7 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43144. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41225] Fermi GRB 251216A: Global MASTER-Net observations report
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43143 SUBJECT: Fermi GRB 251216A: Global MASTER-Net observations report DATE: 25/12/16 15:15:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251216A ( Fermi GBM team, GCN 43139) errorbox 17500 sec after notice time and 17536 sec after trigger time at 2025-12-16 14:30:26 UT, with upper limit up to 16.4 mag. Observations started at twilight. The observations began at zenith distance = 39 deg. The sun altitude is -9.5 deg. The galactic latitude b = 16 deg., longitude l = 84 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3072907 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 10659 | 2025-12-16 12:35:18 | MASTER- | (18h 38m 20.71s , +53d 19m 42.3s) | C | 60 | 16.9 | 10659 | 2025-12-16 12:35:18 | MASTER- | (18h 34m 27.90s , +54d 21m 36.1s) | C | 60 | 18.4 | 10732 | 2025-12-16 12:36:31 | MASTER- | (19h 08m 51.53s , +57d 04m 35.2s) | C | 60 | 16.8 | 10732 | 2025-12-16 12:36:31 | MASTER- | (19h 04m 35.12s , +58d 06m 38.4s) | C | 60 | 18.6 | 10803 | 2025-12-16 12:37:43 | MASTER- | (18h 39m 15.37s , +51d 24m 37.8s) | C | 60 | 16.9 | 10804 | 2025-12-16 12:37:43 | MASTER- | (18h 35m 33.19s , +52d 26m 36.2s) | C | 60 | 18.3 | 10876 | 2025-12-16 12:38:55 | MASTER- | (18h 38m 26.95s , +55d 13m 43.2s) | C | 60 | 17.2 | 10876 | 2025-12-16 12:38:55 | MASTER- | (18h 34m 24.25s , +56d 15m 38.2s) | C | 60 | 18.5 | 10948 | 2025-12-16 12:40:07 | MASTER- | (18h 40m 06.35s , +57d 07m 35.6s) | C | 60 | 17.5 | 10948 | 2025-12-16 12:40:07 | MASTER- | (18h 35m 51.37s , +58d 09m 31.1s) | C | 60 | 18.8 | 11020 | 2025-12-16 12:41:19 | MASTER- | (18h 17m 27.03s , +49d 32m 48.1s) | C | 60 | 17.3 | 11020 | 2025-12-16 12:41:19 | MASTER- | (18h 13m 54.31s , +50d 34m 39.8s) | C | 60 | 18.7 | 11090 | 2025-12-16 12:42:29 | MASTER- | (18h 21m 25.26s , +47d 38m 46.3s) | C | 60 | 17.0 | 11090 | 2025-12-16 12:42:29 | MASTER- | (18h 18m 00.39s , +48d 40m 42.0s) | C | 60 | 18.5 | 11162 | 2025-12-16 12:43:41 | MASTER- | (19h 05m 47.90s , +55d 11m 36.3s) | C | 60 | 16.7 | 11162 | 2025-12-16 12:43:41 | MASTER- | (19h 01m 45.00s , +56d 13m 43.0s) | C | 60 | 18.4 | 11236 | 2025-12-16 12:44:55 | MASTER- | (18h 14m 21.88s , +51d 27m 57.8s) | C | 60 | 17.6 | 11236 | 2025-12-16 12:44:56 | MASTER- | (18h 10m 40.69s , +52d 29m 48.2s) | C | 60 | 19.0 | 11308 | 2025-12-16 12:46:07 | MASTER- | (18h 12m 17.10s , +53d 21m 26.9s) | C | 60 | 18.0 | 11379 | 2025-12-16 12:47:18 | MASTER- | (18h 11m 09.66s , +55d 15m 24.9s) | C | 60 | 18.0 | 11592 | 2025-12-16 12:50:51 | MASTER- | (18h 37m 50.00s , +50d 33m 22.3s) | C | 60 | 18.4 | 11592 | 2025-12-16 12:50:51 | MASTER- | (18h 41m 22.81s , +49d 31m 20.8s) | C | 60 | 16.8 | 11662 | 2025-12-16 12:52:02 | MASTER- | (18h 23m 00.92s , +46d 46m 30.2s) | C | 60 | 18.5 | 11662 | 2025-12-16 12:52:02 | MASTER- | (18h 26m 18.41s , +45d 44m 32.4s) | C | 60 | 17.1 | 11734 | 2025-12-16 12:53:13 | MASTER- | (19h 00m 27.50s , +54d 20m 11.0s) | C | 60 | 18.2 | 11734 | 2025-12-16 12:53:13 | MASTER- | (19h 04m 18.96s , +53d 18m 04.3s) | C | 60 | 16.7 | 12313 | 2025-12-16 13:02:52 | MASTER- | (19h 00m 30.09s , +52d 26m 38.2s) | C | 60 | 18.0 | 12313 | 2025-12-16 13:02:52 | MASTER- | (19h 04m 12.17s , +51d 24m 33.7s) | C | 60 | 16.8 | 12386 | 2025-12-16 13:04:05 | MASTER- | (18h 41m 05.95s , +48d 40m 19.4s) | C | 60 | 18.2 | 12386 | 2025-12-16 13:04:05 | MASTER- | (18h 44m 31.00s , +47d 38m 20.4s) | C | 60 | 16.8 | 12462 | 2025-12-16 13:05:21 | MASTER- | (19h 33m 25.72s , +58d 05m 27.0s) | C | 60 | 18.6 | 12462 | 2025-12-16 13:05:21 | MASTER- | (19h 37m 41.47s , +57d 03m 16.7s) | C | 60 | 16.9 | 13173 | 2025-12-16 13:17:12 | MASTER- | (19h 01m 48.72s , +50d 33m 15.2s) | C | 60 | 17.1 | 13173 | 2025-12-16 13:17:12 | MASTER- | (19h 03m 38.43s , +49d 31m 52.6s) | C | 60 | 16.2 | 13244 | 2025-12-16 13:18:23 | MASTER- | (19h 26m 40.81s , +54d 18m 19.9s) | C | 60 | 16.9 | 13244 | 2025-12-16 13:18:23 | MASTER- | (19h 28m 40.23s , +53d 16m 50.2s) | C | 60 | 15.8 | 13448 | 2025-12-16 13:21:47 | MASTER- | (18h 45m 14.40s , +46d 46m 00.1s) | C | 60 | 16.7 | 13448 | 2025-12-16 13:21:47 | MASTER- | (18h 46m 55.96s , +45d 44m 41.8s) | C | 60 | 16.1 | 13660 | 2025-12-16 13:25:19 | MASTER- | (19h 05m 51.95s , +47d 37m 13.2s) | C | 60 | 15.7 | 13660 | 2025-12-16 13:25:19 | MASTER- | (19h 04m 06.22s , +48d 38m 39.8s) | C | 60 | 16.3 | 13876 | 2025-12-16 13:28:55 | MASTER- | (20h 12m 11.03s , +58d 56m 54.9s) | C | 60 | 15.8 | 17567 | 2025-12-16 14:30:26 | MASTER-Kislovodsk | (19h 11m 54.53s , +50d 38m 45.8s) | C | 60 | 12.7 | 17567 | 2025-12-16 14:30:26 | MASTER-Kislovodsk | (19h 05m 06.15s , +50d 59m 03.9s) | C | 60 | 15.6 | 17646 | 2025-12-16 14:31:46 | MASTER-Kislovodsk | (19h 12m 58.52s , +54d 27m 44.3s) | C | 60 | 12.5 | 17646 | 2025-12-16 14:31:46 | MASTER-Kislovodsk | (19h 05m 29.24s , +54d 48m 25.8s) | C | 60 | 15.5 | 17726 | 2025-12-16 14:33:05 | MASTER-Kislovodsk | (19h 41m 23.34s , +52d 34m 21.3s) | C | 60 | 13.1 | 17726 | 2025-12-16 14:33:05 | MASTER-Kislovodsk | (19h 34m 12.59s , +52d 54m 40.2s) | C | 60 | 15.1 | 17806 | 2025-12-16 14:34:25 | MASTER-Kislovodsk | (19h 33m 39.17s , +54d 28m 28.9s) | C | 60 | 12.6 | 17806 | 2025-12-16 14:34:25 | MASTER-Kislovodsk | (19h 26m 10.96s , +54d 49m 21.1s) | C | 60 | 15.7 | 17892 | 2025-12-16 14:35:51 | MASTER-Kislovodsk | (19h 01m 46.32s , +52d 33m 50.3s) | C | 60 | 12.7 | 17892 | 2025-12-16 14:35:51 | MASTER-Kislovodsk | (18h 54m 42.14s , +52d 54m 07.7s) | C | 60 | 15.5 | 17992 | 2025-12-16 14:37:32 | MASTER-Kislovodsk | (19h 40m 34.70s , +48d 46m 44.1s) | C | 60 | 13.3 | 17992 | 2025-12-16 14:37:32 | MASTER-Kislovodsk | (19h 34m 00.53s , +49d 07m 08.5s) | C | 60 | 15.9 | 18072 | 2025-12-16 14:38:52 | MASTER-Kislovodsk | (19h 04m 00.90s , +48d 43m 49.3s) | C | 60 | 13.6 | 18072 | 2025-12-16 14:38:52 | MASTER-Kislovodsk | (18h 57m 32.23s , +49d 04m 10.6s) | C | 60 | 16.2 | 18152 | 2025-12-16 14:40:12 | MASTER-Kislovodsk | (19h 26m 23.52s , +56d 22m 48.8s) | C | 60 | 13.3 | 18152 | 2025-12-16 14:40:12 | MASTER-Kislovodsk | (19h 18m 33.48s , +56d 42m 51.8s) | C | 60 | 16.1 | 18235 | 2025-12-16 14:41:34 | MASTER-Kislovodsk | (19h 49m 49.49s , +50d 41m 24.3s) | C | 60 | 13.6 | 18235 | 2025-12-16 14:41:34 | MASTER-Kislovodsk | (19h 42m 55.13s , +51d 02m 14.9s) | C | 60 | 16.0 | 18315 | 2025-12-16 14:42:54 | MASTER-Kislovodsk | (18h 52m 48.80s , +50d 38m 56.0s) | C | 60 | 13.8 | 18315 | 2025-12-16 14:42:54 | MASTER-Kislovodsk | (18h 46m 05.95s , +50d 59m 17.0s) | C | 60 | 16.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43143. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41224] GRB 251202A/EP251202a: Koshka optical upper limit
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43142 SUBJECT: GRB 251202A/EP251202a: Koshka optical upper limit DATE: 25/12/16 14:47:43 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), A. Novichonok (Petrozavodsk State University, KIAM), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 251202A/EP251202a (Fermi GBM team, GCN 42933; Zhang et al., GCN 42937; Sbarufatti et al., GCN 42943; Liang et al., GCN 42946; Bala, GCN 42957; Arya et al., GCN 42967; Guo et al., GCN 42970, GCN 42997) with the Zeiss-1000 telescope of the Simeiz (Koshka) observatory (INASAN) taking several 90-second expositions in R-band starting on Dec.05 UT 21:38:48. In the stacked image we do not detect the optical counterpart reported previously (Zhu et al., GCN 42939; O’Neill et al., GCN 42947; Quirola-Vasquez et al., GCN 42948; Kuin and Moss, GCN 42956; Zheng et al., GCN 42964; Ma et al., GCN 42966; Bochenek et al., GCN 42977; Contreras et al., GCN 42999; Giarratana et al., GCN 43128). Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-05 21:38:48 3.86988 68*90 R n/d n/d 19.7 Simeiz/Zeiss-1000 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43142. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41223] GRB 251214B: Mondy optical upper limit
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43141 SUBJECT: GRB 251214B: Mondy optical upper limit DATE: 25/12/16 13:49:15 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), E. Klunko (ISTP), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112; Laha et al., GCN 43129), and GECAM-B (Luo et al., GCN 43113) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) taking several 120-second expositions in R-band starting on Dec.15 UT 11:36:28. In the stacked image we do not detect the optical counterpart reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123; Volnova et al., GCN 43124; de Ugarte Postigo et al., GCN 43131; Pankov et al., GCN 43132; Lin et al., GCN 43134). Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-15 11:36:28 1.12792 30*120 R n/d n/d 22.6 Mondy/AZT-33IK The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43141. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41222] GRB 251215A: COLIBRÍ optical upper limit
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43140 SUBJECT: GRB 251215A: COLIBRÍ optical upper limit DATE: 25/12/16 12:53:38 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Stéphane Basa (UAR Pytheas), Leonardo García García (UNAM), Benjamin Schneider (LAM), Noémie Globus (UNAM), Jean-Luc Atteia (IRAP), William H. Lee (UNAM), Alan M. Watson (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Enrique Moreno Méndez (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM). We imaged the field of GRB 251215A detected by Fermi (Fermi GBM team, GCN Circ. 43104) and confirmed by Swift/BAT-GUANO (Ronchini et al., GCN Circ. 43114) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-15 at 11:27:37.35 to 12:06:41.62 UTC (from 7.10 to 7.76 hr after the Fermi trigger) and obtained 31 minutes of simultaneous exposure in the r and z filters. Observations were obtained at a relatively high airmass (~3.0), and we also noted that the Galactic extinction is significant at the Swift/BAT-GUANO localization (Av= ~2.8). The data were reduced, coadded and analyzed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the SkyMapper-DR4 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source associated with the candidates reported by Swift-XRT (Osborne et al., GCN Circ. 43137) down to the following 5-sigma limit: r > 21.8 z > 20.5 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43140. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41221] GRB 251216A: Fermi GBM Final Real-time Localization
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43139 SUBJECT: GRB 251216A: Fermi GBM Final Real-time Localization DATE: 25/12/16 09:48:49 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 09:38:09 UT on 16 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251216A (trigger 787570694.65431 / 251216401). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 290.9, Dec = 52.0 (J2000 degrees, equivalent to J2000 19h 23m, 52d 00'), with a statistical uncertainty of 9.3 degrees. The angle from the Fermi LAT boresight is 42.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251216401/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251216401/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251216401/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43139. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41220] EP251214b: KAIT optical upper limit
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43138 SUBJECT: EP251214b: KAIT optical upper limit DATE: 25/12/16 08:38:39 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP251214b (Jiang et al., GCN 43125) starting at 08:17, Dec 14 UT, about 0.95 hours after the trigger. A set of 29x60s and again 40x60s clear (roughly R) filter images were obtained. In our coadd images, we did not detect any new source within the EP-WXT error circle (Jiang et al., GCN 43125) down to limiting mag of 20.8 and 21.5 mag (Vega) at a mid-time of 1.23 and 3.12 hours after the trigger. Our result is consistent with the upper limit reported by other groups (Eyles-Ferris et al., GCN 43117; Lipunov et al., GCN 43127). View this GCN Circular online at https://gcn.nasa.gov/circulars/43138. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41219] GRB 251215A: Swift-XRT observations
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43137 SUBJECT: GRB 251215A: Swift-XRT observations DATE: 25/12/16 08:06:33 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 251215A, collecting 5.2 ks of Photon Counting (PC) mode data between T0+32.0 ks and T0+49.6 ks. Four uncatalogued X-ray sources have been detected within the estimated 3-sigma Swift/BAT error region (493 arcsec), however none of them is above historical upper limits, or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 2: RA (J2000.0): 122.5523 = 08h 10m 12.54s Dec (J2000.0): -36.6697 = -36d 40' 10.8" Error: 3.9 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (9.7 [+1.8, -1.7])e-3 ct s^-1 Distance: 383 arcsec from Swift/BAT position. Flux: (4.47 [+0.81, -0.77])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 5: RA (J2000.0): 122.6189 = 08h 10m 28.54s Dec (J2000.0): -36.7427 = -36d 44' 33.6" Error: 5.7 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (5.0 [+1.3, -1.2])e-3 ct s^-1 Distance: 97 arcsec from Swift/BAT position. Flux: (1.96 [+0.50, -0.47])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 6: RA (J2000.0): 122.6954 = 08h 10m 46.90s Dec (J2000.0): -36.6198 = -36d 37' 11.5" Error: 7.1 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (3.44 [+1.20, -0.99])e-3 ct s^-1 Distance: 448 arcsec from Swift/BAT position. Flux: (2.87 [+1.00, -0.83])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 8: RA (J2000.0): 122.6662 = 08h 10m 39.88s Dec (J2000.0): -36.6483 = -36d 38' 53.8" Error: 5.9 arcsec (radius, 90% conf.) Count-rate: (1.81 [+0.92, -0.72])e-3 ct s^-1 Distance: 330 arcsec from Swift/BAT position. Flux: (3.7 [+1.9, -1.5])e-10 erg cm^-2 s^-1 (observed, 0.3-10 keV) A catalogued source was also detected within the estimated 3-sigma Swift/BAT error region (493 arcsec). Two uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021894. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43137. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41218] Fermi GRB 251215A: Global MASTER-Net observations report
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43136 SUBJECT: Fermi GRB 251215A: Global MASTER-Net observations report DATE: 25/12/16 07:30:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 251215A ( Fermi GBM team, GCN 43104) errorbox 708 sec after notice time and 729 sec after trigger time at 2025-12-15 04:33:30 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 25 deg. The sun altitude is -35.7 deg. The galactic latitude b = -12 deg., longitude l = 256 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3071404 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 759 | 2025-12-15 04:33:30 | MASTER-OAFA | (07h 21m 38.63s , -44d 11m 53.3s) | C | 60 | 19.8 | 836 | 2025-12-15 04:34:47 | MASTER-OAFA | (07h 32m 44.70s , -44d 12m 40.8s) | C | 60 | 19.7 | 1278 | 2025-12-15 04:42:09 | MASTER-OAFA | (07h 21m 33.82s , -44d 13m 28.4s) | C | 60 | 20.1 | 1356 | 2025-12-15 04:43:27 | MASTER-OAFA | (07h 32m 50.29s , -44d 13m 23.2s) | C | 60 | 20.0 | 1537 | 2025-12-15 04:46:28 | MASTER-OAFA | (07h 21m 36.90s , -44d 13m 08.5s) | C | 60 | 20.2 | 1616 | 2025-12-15 04:47:47 | MASTER-OAFA | (07h 28m 30.24s , -42d 18m 18.6s) | C | 60 | 19.8 | 1692 | 2025-12-15 04:49:03 | MASTER-OAFA | (07h 39m 20.70s , -42d 17m 18.4s) | C | 60 | 19.5 | 1768 | 2025-12-15 04:50:19 | MASTER-OAFA | (07h 28m 37.49s , -42d 18m 11.5s) | C | 60 | 19.8 | 1844 | 2025-12-15 04:51:35 | MASTER-OAFA | (07h 39m 20.66s , -42d 19m 12.0s) | C | 60 | 19.5 | 1920 | 2025-12-15 04:52:51 | MASTER-OAFA | (07h 28m 37.47s , -42d 18m 57.2s) | C | 60 | 19.8 | 1998 | 2025-12-15 04:54:09 | MASTER-OAFA | (07h 14m 43.71s , -46d 06m 35.4s) | C | 60 | 20.3 | 2073 | 2025-12-15 04:55:24 | MASTER-OAFA | (07h 26m 20.85s , -46d 05m 09.8s) | C | 60 | 20.3 | 2149 | 2025-12-15 04:56:40 | MASTER-OAFA | (07h 14m 41.57s , -46d 05m 53.1s) | C | 60 | 20.3 | 2225 | 2025-12-15 04:57:56 | MASTER-OAFA | (07h 26m 14.02s , -46d 04m 51.5s) | C | 60 | 20.3 | 4916 | 2025-12-15 05:42:47 | MASTER-OAFA | (07h 32m 47.05s , -44d 22m 53.9s) | C | 60 | 20.1 | 4992 | 2025-12-15 05:44:03 | MASTER-OAFA | (07h 32m 47.23s , -44d 24m 00.4s) | C | 60 | 20.1 | 5071 | 2025-12-15 05:45:22 | MASTER-OAFA | (07h 32m 50.60s , -44d 22m 25.2s) | C | 60 | 20.1 | 5147 | 2025-12-15 05:46:38 | MASTER-OAFA | (07h 21m 35.26s , -44d 22m 27.4s) | C | 60 | 20.3 | 5224 | 2025-12-15 05:47:55 | MASTER-OAFA | (07h 21m 40.10s , -44d 23m 25.8s) | C | 60 | 20.2 | 5301 | 2025-12-15 05:49:12 | MASTER-OAFA | (07h 21m 35.65s , -44d 24m 24.1s) | C | 60 | 20.2 | 5377 | 2025-12-15 05:50:28 | MASTER-OAFA | (07h 39m 26.43s , -42d 29m 44.8s) | C | 60 | 19.6 | 5454 | 2025-12-15 05:51:45 | MASTER-OAFA | (07h 39m 23.79s , -42d 28m 14.2s) | C | 60 | 19.6 | 5530 | 2025-12-15 05:53:01 | MASTER-OAFA | (07h 39m 23.97s , -42d 29m 57.9s) | C | 60 | 19.6 | 5607 | 2025-12-15 05:54:18 | MASTER-OAFA | (07h 28m 37.31s , -42d 28m 27.7s) | C | 60 | 19.8 | 5746 | 2025-12-15 05:56:37 | MASTER-OAFA | (07h 28m 32.75s , -42d 29m 10.7s) | C | 60 | 19.8 | 5832 | 2025-12-15 05:58:03 | MASTER-OAFA | (07h 28m 33.73s , -42d 28m 08.7s) | C | 60 | 19.8 | 8125 | 2025-12-15 06:36:16 | MASTER-OAFA | (07h 26m 26.02s , -46d 16m 45.3s) | C | 60 | 20.1 | 8202 | 2025-12-15 06:37:33 | MASTER-OAFA | (07h 26m 23.77s , -46d 15m 06.7s) | C | 60 | 20.1 | 8279 | 2025-12-15 06:38:50 | MASTER-OAFA | (07h 26m 24.09s , -46d 16m 48.0s) | C | 60 | 20.1 | 8360 | 2025-12-15 06:40:11 | MASTER-OAFA | (07h 14m 56.32s , -46d 15m 39.0s) | C | 60 | 20.1 | 8435 | 2025-12-15 06:41:26 | MASTER-OAFA | (07h 14m 50.27s , -46d 16m 09.0s) | C | 60 | 20.1 | 8510 | 2025-12-15 06:42:42 | MASTER-OAFA | (07h 14m 49.98s , -46d 15m 07.3s) | C | 60 | 20.2 | 9066 | 2025-12-15 06:51:57 | MASTER-OAFA | (07h 32m 54.70s , -44d 21m 49.3s) | C | 60 | 20.1 | 9146 | 2025-12-15 06:53:17 | MASTER-OAFA | (07h 32m 54.52s , -44d 20m 48.2s) | C | 60 | 20.1 | 9222 | 2025-12-15 06:54:33 | MASTER-OAFA | (07h 33m 00.52s , -44d 21m 46.6s) | C | 60 | 20.0 | 9300 | 2025-12-15 06:55:51 | MASTER-OAFA | (07h 21m 52.29s , -44d 22m 38.3s) | C | 60 | 20.1 | 9375 | 2025-12-15 06:57:06 | MASTER-OAFA | (07h 21m 49.58s , -44d 21m 12.2s) | C | 60 | 20.1 | 9449 | 2025-12-15 06:58:20 | MASTER-OAFA | (07h 21m 49.84s , -44d 22m 43.6s) | C | 60 | 20.1 | 9528 | 2025-12-15 06:59:39 | MASTER-OAFA | (07h 39m 36.92s , -42d 26m 56.9s) | C | 60 | 19.5 | 9602 | 2025-12-15 07:00:53 | MASTER-OAFA | (07h 39m 31.12s , -42d 27m 41.8s) | C | 60 | 19.5 | 9685 | 2025-12-15 07:02:16 | MASTER-OAFA | (07h 39m 30.42s , -42d 26m 40.3s) | C | 60 | 19.5 | 9761 | 2025-12-15 07:03:32 | MASTER-OAFA | (07h 28m 49.41s , -42d 27m 49.0s) | C | 60 | 19.8 | 9836 | 2025-12-15 07:04:47 | MASTER-OAFA | (07h 28m 43.69s , -42d 28m 48.0s) | C | 60 | 19.8 | 9911 | 2025-12-15 07:06:02 | MASTER-OAFA | (07h 28m 49.61s , -42d 28m 43.1s) | C | 60 | 19.8 | 9989 | 2025-12-15 07:07:20 | MASTER-OAFA | (07h 08m 14.54s , -42d 29m 07.5s) | C | 60 | 20.1 | 10066 | 2025-12-15 07:08:37 | MASTER-OAFA | (07h 19m 05.86s , -42d 26m 59.3s) | C | 60 | 19.9 | 10144 | 2025-12-15 07:09:55 | MASTER-OAFA | (07h 08m 12.74s , -42d 28m 07.0s) | C | 60 | 20.1 | 10220 | 2025-12-15 07:11:11 | MASTER-OAFA | (07h 19m 01.00s , -42d 26m 52.3s) | C | 60 | 19.9 | 10296 | 2025-12-15 07:12:27 | MASTER-OAFA | (07h 08m 18.47s , -42d 28m 04.8s) | C | 60 | 20.0 | 10373 | 2025-12-15 07:13:44 | MASTER-OAFA | (07h 26m 28.67s , -46d 16m 19.5s) | C | 60 | 20.2 | 10447 | 2025-12-15 07:14:58 | MASTER-OAFA | (07h 26m 35.57s , -46d 16m 13.5s) | C | 60 | 20.2 | 10523 | 2025-12-15 07:16:14 | MASTER-OAFA | (07h 26m 32.19s , -46d 14m 44.0s) | C | 60 | 20.2 | 10599 | 2025-12-15 07:17:30 | MASTER-OAFA | (07h 15m 01.09s , -46d 16m 24.8s) | C | 60 | 20.2 | 10676 | 2025-12-15 07:18:47 | MASTER-OAFA | (07h 15m 04.61s , -46d 14m 26.7s) | C | 60 | 20.2 | 10752 | 2025-12-15 07:20:03 | MASTER-OAFA | (07h 14m 57.99s , -46d 15m 24.1s) | C | 60 | 20.2 | 11089 | 2025-12-15 07:25:40 | MASTER-OAFA | (07h 33m 04.54s , -44d 22m 09.2s) | C | 60 | 20.1 | 11164 | 2025-12-15 07:26:55 | MASTER-OAFA | (07h 33m 08.71s , -44d 20m 17.2s) | C | 60 | 20.0 | 11240 | 2025-12-15 07:28:11 | MASTER-OAFA | (07h 33m 02.78s , -44d 21m 08.0s) | C | 60 | 20.1 | 11321 | 2025-12-15 07:29:32 | MASTER-OAFA | (07h 00m 48.69s , -44d 21m 46.6s) | C | 60 | 20.3 | 11397 | 2025-12-15 07:30:48 | MASTER-OAFA | (07h 11m 51.63s , -44d 22m 30.7s) | C | 60 | 20.2 | 11473 | 2025-12-15 07:32:04 | MASTER-OAFA | (07h 00m 48.56s , -44d 22m 37.0s) | C | 60 | 20.2 | 11549 | 2025-12-15 07:33:20 | MASTER-OAFA | (07h 11m 55.05s , -44d 20m 30.4s) | C | 60 | 20.2 | 11626 | 2025-12-15 07:34:37 | MASTER-OAFA | (07h 00m 46.36s , -44d 22m 19.2s) | C | 60 | 20.2 | 11705 | 2025-12-15 07:35:56 | MASTER-OAFA | (07h 39m 43.96s , -42d 26m 19.8s) | C | 60 | 19.5 | 11780 | 2025-12-15 07:37:11 | MASTER-OAFA | (07h 39m 37.07s , -42d 27m 04.2s) | C | 60 | 19.4 | 11855 | 2025-12-15 07:38:26 | MASTER-OAFA | (07h 39m 38.58s , -42d 26m 03.1s) | C | 60 | 19.5 | 11935 | 2025-12-15 07:39:46 | MASTER-OAFA | (07h 30m 51.44s , -48d 09m 35.4s) | C | 60 | 20.1 | 12010 | 2025-12-15 07:41:01 | MASTER-OAFA | (07h 42m 55.59s , -48d 09m 06.7s) | C | 60 | 19.9 | 12087 | 2025-12-15 07:42:18 | MASTER-OAFA | (07h 30m 55.70s , -48d 07m 49.7s) | C | 60 | 20.0 | 12162 | 2025-12-15 07:43:34 | MASTER-OAFA | (07h 42m 52.36s , -48d 09m 05.7s) | C | 60 | 19.9 | 12240 | 2025-12-15 07:44:51 | MASTER-OAFA | (07h 30m 58.65s , -48d 07m 43.9s) | C | 60 | 20.0 | 12318 | 2025-12-15 07:46:09 | MASTER-OAFA | (07h 19m 06.95s , -42d 27m 23.2s) | C | 60 | 19.9 | 12395 | 2025-12-15 07:47:26 | MASTER-OAFA | (07h 19m 08.53s , -42d 26m 22.2s) | C | 60 | 19.9 | 12471 | 2025-12-15 07:48:42 | MASTER-OAFA | (07h 19m 14.47s , -42d 27m 21.2s) | C | 60 | 19.8 | 12546 | 2025-12-15 07:49:57 | MASTER-OAFA | (07h 08m 19.27s , -42d 28m 36.9s) | C | 60 | 20.1 | 12620 | 2025-12-15 07:51:11 | MASTER-OAFA | (07h 08m 26.14s , -42d 28m 23.2s) | C | 60 | 20.0 | 12694 | 2025-12-15 07:52:25 | MASTER-OAFA | (07h 08m 23.68s , -42d 27m 05.0s) | C | 60 | 20.0 | 12771 | 2025-12-15 07:53:42 | MASTER-OAFA | (07h 26m 40.50s , -46d 15m 33.7s) | C | 60 | 20.1 | 12850 | 2025-12-15 07:55:01 | MASTER-OAFA | (07h 26m 43.84s , -46d 13m 52.0s) | C | 60 | 20.1 | 12927 | 2025-12-15 07:56:18 | MASTER-OAFA | (07h 26m 38.20s , -46d 14m 34.8s) | C | 60 | 20.1 | 13003 | 2025-12-15 07:57:35 | MASTER-OAFA | (07h 37m 07.47s , -46d 14m 21.4s) | C | 60 | 20.0 | 13080 | 2025-12-15 07:58:51 | MASTER-OAFA | (07h 48m 32.47s , -46d 15m 08.4s) | C | 60 | 19.8 | 13155 | 2025-12-15 08:00:06 | MASTER-OAFA | (07h 37m 06.85s , -46d 15m 15.8s) | C | 60 | 20.0 | 13238 | 2025-12-15 08:01:29 | MASTER-OAFA | (07h 48m 35.83s , -46d 13m 17.2s) | C | 60 | 19.8 | 13314 | 2025-12-15 08:02:45 | MASTER-OAFA | (07h 37m 05.08s , -46d 15m 00.9s) | C | 60 | 19.9 | 13434 | 2025-12-15 08:04:46 | MASTER-OAFA | (07h 11m 59.20s , -44d 06m 31.8s) | C | 60 | 20.1 | 13510 | 2025-12-15 08:06:02 | MASTER-OAFA | (07h 11m 53.69s , -44d 07m 07.7s) | C | 60 | 20.1 | 13588 | 2025-12-15 08:07:19 | MASTER-OAFA | (07h 11m 53.62s , -44d 06m 07.0s) | C | 60 | 20.1 | 13663 | 2025-12-15 08:08:34 | MASTER-OAFA | (07h 00m 50.69s , -44d 07m 25.0s) | C | 60 | 20.1 | 13738 | 2025-12-15 08:09:49 | MASTER-OAFA | (07h 00m 44.20s , -44d 08m 24.8s) | C | 60 | 20.1 | 13812 | 2025-12-15 08:11:03 | MASTER-OAFA | (07h 00m 49.56s , -44d 08m 05.9s) | C | 60 | 20.0 | 13890 | 2025-12-15 08:12:21 | MASTER-OAFA | (07h 15m 57.41s , -40d 19m 43.9s) | C | 60 | 19.7 | 13966 | 2025-12-15 08:13:37 | MASTER-OAFA | (07h 26m 31.11s , -40d 17m 39.3s) | C | 60 | 19.5 | 14043 | 2025-12-15 08:14:54 | MASTER-OAFA | (07h 15m 54.78s , -40d 18m 47.7s) | C | 60 | 19.6 | 14120 | 2025-12-15 08:16:11 | MASTER-OAFA | (07h 26m 24.87s , -40d 17m 30.7s) | C | 60 | 19.4 | 14197 | 2025-12-15 08:17:28 | MASTER-OAFA | (07h 16m 00.19s , -40d 18m 46.2s) | C | 60 | 19.4 | 14275 | 2025-12-15 08:18:46 | MASTER-OAFA | (07h 42m 53.06s , -47d 55m 28.5s) | C | 60 | 19.4 | 14352 | 2025-12-15 08:20:03 | MASTER-OAFA | (07h 42m 57.59s , -47d 55m 10.4s) | C | 60 | 19.3 | 14427 | 2025-12-15 08:21:18 | MASTER-OAFA | (07h 42m 55.69s , -47d 53m 44.8s) | C | 60 | 19.3 | 14504 | 2025-12-15 08:22:35 | MASTER-OAFA | (07h 30m 58.35s , -47d 55m 18.9s) | C | 60 | 19.3 | 14579 | 2025-12-15 08:23:50 | MASTER-OAFA | (07h 31m 01.75s , -47d 53m 57.1s) | C | 60 | 19.3 | 14655 | 2025-12-15 08:25:06 | MASTER-OAFA | (07h 30m 55.68s , -47d 54m 41.6s) | C | 60 | 19.2 | 14732 | 2025-12-15 08:26:23 | MASTER-OAFA | (07h 19m 09.09s , -42d 11m 42.9s) | C | 60 | 18.9 | 14811 | 2025-12-15 08:27:42 | MASTER-OAFA | (07h 19m 16.77s , -42d 12m 42.0s) | C | 60 | 18.8 | 14886 | 2025-12-15 08:28:57 | MASTER-OAFA | (07h 19m 09.57s , -42d 13m 41.9s) | C | 60 | 18.7 | 14967 | 2025-12-15 08:30:18 | MASTER-OAFA | (07h 20m 16.60s , -47d 54m 16.6s) | C | 60 | 18.7 | 15042 | 2025-12-15 08:31:33 | MASTER-OAFA | (07h 20m 11.22s , -47d 54m 54.2s) | C | 60 | 18.5 | 15122 | 2025-12-15 08:32:53 | MASTER-OAFA | (07h 48m 34.22s , -45d 59m 04.2s) | C | 60 | 18.2 | 15200 | 2025-12-15 08:34:11 | MASTER-OAFA | (07h 48m 40.65s , -46d 00m 03.4s) | C | 60 | 18.1 | 15278 | 2025-12-15 08:35:29 | MASTER-OAFA | (07h 48m 34.37s , -46d 01m 03.0s) | C | 60 | 18.0 | 15353 | 2025-12-15 08:36:44 | MASTER-OAFA | (07h 37m 07.92s , -46d 01m 09.9s) | C | 60 | 14.4 | 84349 | 2025-12-16 03:46:40 | MASTER-OAFA | (06h 42m 04.68s , -46d 22m 13.0s) | C | 60 | 20.1 | 84423 | 2025-12-16 03:47:55 | MASTER-OAFA | (06h 42m 11.05s , -46d 21m 55.7s) | C | 60 | 20.1 | 84501 | 2025-12-16 03:49:12 | MASTER-OAFA | (06h 42m 08.07s , -46d 20m 26.7s) | C | 60 | 20.1 | 85037 | 2025-12-16 03:58:08 | MASTER-OAFA | (07h 03m 41.56s , -38d 45m 25.1s) | C | 60 | 20.0 | 85111 | 2025-12-16 03:59:22 | MASTER-OAFA | (07h 03m 39.52s , -38d 43m 41.8s) | C | 60 | 20.0 | 85186 | 2025-12-16 04:00:37 | MASTER-OAFA | (07h 03m 39.60s , -38d 45m 13.1s) | C | 60 | 20.0 | 85269 | 2025-12-16 04:02:00 | MASTER-OAFA | (07h 13m 56.14s , -38d 43m 24.5s) | C | 60 | 19.9 | 85346 | 2025-12-16 04:03:17 | MASTER-OAFA | (07h 13m 49.92s , -38d 44m 16.0s) | C | 60 | 19.9 | 85426 | 2025-12-16 04:04:37 | MASTER-OAFA | (07h 13m 50.59s , -38d 43m 13.4s) | C | 60 | 19.9 | 86212 | 2025-12-16 04:17:43 | MASTER-OAFA | (07h 00m 35.46s , -50d 09m 13.0s) | C | 60 | 20.0 | 86286 | 2025-12-16 04:18:57 | MASTER-OAFA | (07h 00m 41.92s , -50d 08m 46.7s) | C | 60 | 19.9 | 86361 | 2025-12-16 04:20:12 | MASTER-OAFA | (07h 00m 39.05s , -50d 07m 11.0s) | C | 60 | 19.9 | 86437 | 2025-12-16 04:21:28 | MASTER-OAFA | (07h 13m 05.48s , -50d 08m 41.6s) | C | 60 | 19.9 | 86511 | 2025-12-16 04:22:42 | MASTER-OAFA | (07h 13m 09.00s , -50d 07m 10.9s) | C | 60 | 19.9 | 86586 | 2025-12-16 04:23:57 | MASTER-OAFA | (07h 13m 03.32s , -50d 08m 00.5s) | C | 60 | 19.9 | 87136 | 2025-12-16 04:33:07 | MASTER-OAFA | (07h 11m 30.33s , -34d 54m 46.1s) | C | 60 | 20.0 | 88145 | 2025-12-16 04:49:56 | MASTER-OAFA | (06h 39m 07.90s , -44d 26m 10.3s) | C | 60 | 20.2 | 88223 | 2025-12-16 04:51:14 | MASTER-OAFA | (06h 39m 04.26s , -44d 24m 24.1s) | C | 60 | 20.2 | 88298 | 2025-12-16 04:52:29 | MASTER-OAFA | (06h 39m 04.43s , -44d 25m 58.7s) | C | 60 | 20.2 | 88374 | 2025-12-16 04:53:45 | MASTER-OAFA | (06h 50m 17.94s , -44d 24m 16.0s) | C | 60 | 20.3 | 88449 | 2025-12-16 04:55:00 | MASTER-OAFA | (06h 50m 11.51s , -44d 25m 01.4s) | C | 60 | 20.3 | 88528 | 2025-12-16 04:56:19 | MASTER-OAFA | (06h 50m 11.32s , -44d 23m 59.0s) | C | 60 | 20.3 | 89158 | 2025-12-16 05:06:49 | MASTER-OAFA | (06h 49m 31.52s , -50d 05m 36.2s) | C | 60 | 20.0 | 89232 | 2025-12-16 05:08:03 | MASTER-OAFA | (06h 49m 37.28s , -50d 06m 33.8s) | C | 60 | 20.1 | 92863 | 2025-12-16 06:08:34 | MASTER-OAFA | (07h 21m 43.31s , -44d 22m 47.0s) | C | 60 | 20.3 | 92938 | 2025-12-16 06:09:49 | MASTER-OAFA | (07h 32m 48.01s , -44d 23m 39.5s) | C | 60 | 20.2 | 93015 | 2025-12-16 06:11:06 | MASTER-OAFA | (07h 21m 44.03s , -44d 23m 25.4s) | C | 60 | 20.2 | 93096 | 2025-12-16 06:12:27 | MASTER-OAFA | (07h 32m 51.29s , -44d 21m 59.3s) | C | 60 | 20.2 | 93171 | 2025-12-16 06:13:42 | MASTER-OAFA | (07h 21m 42.00s , -44d 23m 19.6s) | C | 60 | 20.3 | 94066 | 2025-12-16 06:28:37 | MASTER-OAFA | (07h 28m 39.67s , -42d 29m 10.7s) | C | 60 | 19.9 | 94142 | 2025-12-16 06:29:53 | MASTER-OAFA | (07h 39m 31.59s , -42d 27m 32.3s) | C | 60 | 19.6 | 94221 | 2025-12-16 06:31:12 | MASTER-OAFA | (07h 28m 37.80s , -42d 28m 18.8s) | C | 60 | 19.9 | 94300 | 2025-12-16 06:32:31 | MASTER-OAFA | (07h 39m 25.23s , -42d 27m 09.1s) | C | 60 | 19.6 | 94378 | 2025-12-16 06:33:49 | MASTER-OAFA | (07h 28m 43.67s , -42d 28m 15.8s) | C | 60 | 19.9 | 94457 | 2025-12-16 06:35:08 | MASTER-OAFA | (07h 14m 55.59s , -46d 17m 09.1s) | C | 60 | 20.3 | 94532 | 2025-12-16 06:36:23 | MASTER-OAFA | (07h 26m 24.14s , -46d 15m 26.7s) | C | 60 | 20.3 | 94618 | 2025-12-16 06:37:49 | MASTER-OAFA | (07h 14m 52.84s , -46d 16m 51.5s) | C | 60 | 20.3 | 94698 | 2025-12-16 06:39:09 | MASTER-OAFA | (07h 26m 27.32s , -46d 15m 19.6s) | C | 60 | 20.3 | 94777 | 2025-12-16 06:40:28 | MASTER-OAFA | (07h 14m 49.66s , -46d 16m 04.5s) | C | 60 | 20.3 | 94857 | 2025-12-16 06:41:48 | MASTER-OAFA | (07h 24m 42.74s , -50d 03m 42.8s) | C | 60 | 20.1 | 94933 | 2025-12-16 06:43:05 | MASTER-OAFA | (07h 37m 02.25s , -50d 04m 35.0s) | C | 60 | 20.1 | 95011 | 2025-12-16 06:44:22 | MASTER-OAFA | (07h 24m 42.56s , -50d 04m 27.0s) | C | 60 | 20.1 | 95086 | 2025-12-16 06:45:37 | MASTER-OAFA | (07h 37m 05.24s , -50d 02m 34.5s) | C | 60 | 20.1 | 95163 | 2025-12-16 06:46:54 | MASTER-OAFA | (07h 24m 40.87s , -50d 04m 29.3s) | C | 60 | 20.2 | 95241 | 2025-12-16 06:48:12 | MASTER-OAFA | (07h 32m 59.73s , -44d 21m 03.7s) | C | 60 | 20.2 | 95315 | 2025-12-16 06:49:26 | MASTER-OAFA | (07h 32m 54.82s , -44d 21m 44.8s) | C | 60 | 20.2 | 95481 | 2025-12-16 06:52:12 | MASTER- | (07h 06m 46.38s , -42d 16m 40.2s) | C | 60 | 17.9 | 95481 | 2025-12-16 06:52:12 | MASTER- | (06h 57m 42.70s , -43d 15m 17.5s) | C | 60 | 17.5 | 95552 | 2025-12-16 06:53:23 | MASTER- | (06h 59m 10.83s , -44d 11m 26.1s) | C | 60 | 17.7 | 95552 | 2025-12-16 06:53:23 | MASTER- | (06h 49m 48.76s , -45d 10m 03.7s) | C | 60 | 17.7 | 95627 | 2025-12-16 06:54:38 | MASTER- | (07h 34m 21.14s , -40d 22m 55.6s) | C | 60 | 17.7 | 95627 | 2025-12-16 06:54:38 | MASTER- | (07h 25m 32.71s , -41d 21m 43.9s) | C | 60 | 17.6 | 96781 | 2025-12-16 07:13:52 | MASTER- | (07h 21m 39.36s , -44d 10m 20.1s) | C | 60 | 17.6 | 96781 | 2025-12-16 07:13:53 | MASTER- | (07h 09m 40.36s , -45d 07m 52.4s) | C | 60 | 17.6 | 96854 | 2025-12-16 07:15:05 | MASTER- | (06h 52m 49.25s , -46d 05m 58.2s) | C | 60 | 17.9 | 96854 | 2025-12-16 07:15:05 | MASTER- | (06h 40m 24.86s , -47d 03m 27.2s) | C | 60 | 17.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43136. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41217] EP251214a: Optical upper limit with Kinder observations
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43135 SUBJECT: EP251214a: Optical upper limit with Kinder observations DATE: 25/12/16 04:56:08 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Aryan, T.-W. Chen, H.-Y. Hsiao, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin,J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP251214a (Yin et al., GCN 43087; GCN 43102) using the 40 cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations started at 16:25 UTC on the 14th of December 2025 (MJD 61023.684), 13.97 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the Pan-STARRS1 3Pi (Chambers et al., 2016 arXiv:1612.05560) image using the 'sfft' (Hu et al., 2022, ApJ, 936, 157) algorithm. We do not find any evidence of a new and uncataloged optical counterpart candidate within the 3.1 arcminute error circle of the EP-WXT localization in either the stacked or the difference image. Moreover, we further utilized AutoPhOT to perform PSF photometry. The details of the observations and the measured upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | i | 61023.684 | 13.97 | 300 * 24 | >21.9 | 1".3 | 1.30 Our non-detection is consistent with Basa et al. (GCN 43092); Lipunov et al. (GCN 43099); Zheng et al. (GCN 43110). The absence of any associated optical counterpart down to 21.9 mag with the optical observations starting within 24 hours of its X-ray discovery aligns well with the 'Dark' nature of FXTs (Aryan et al., 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69). The presented magnitude is calibrated using the field stars from the Pan-STARRS DR2 catalog and is not corrected for the expected Galactic foreground extinction of A_i = 0.05 mag in the direction of the transient (Schlafly & Finkbeiner, 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission can be found in Aryan et al. (2025). View this GCN Circular online at https://gcn.nasa.gov/circulars/43135. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41216] GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
by GCN Circulars 16 Dec '25

16 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43134 SUBJECT: GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras DATE: 25/12/16 04:17:28 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Weikang Lin, Guowang Du, Ziwei Li, Brajesh Kumar, Jiayu Qi, Donglin Gao, Yu Pan, Yuan Fang, Xinlei Chen, Xingzhu Zou, Xufeng Zhu, Tao Wang, Jinghua Zhang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: We performed simultaneous multi-band photometric observations of GRB 251214B (Fermi GBM Team, GCN Circ. 43088; Eyles-Ferris et al., GCN Circ. 43089) with the newly installed three mosaic cameras on the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at the Lijiang Observatory. The observations were initiated at 11:31:54UTC2025-12-14 (~2.5 hours after the Swift/BAT trigger). Multiple frames were obtained in uvgriz - bands. The optical counterpart is detected in the stacked images of g, r bands and single frames of i, z bands, but there is no detection in the u and v band stacked images. The preliminary photometric magnitudes and 3-sigma upper limits are listed below. These magnitudes are not corrected for the Galactic extinction in the direction of the burst. UT Start |Band | Exposure(s)| mag/LimMag (AB) ---------------------|-----|------------|---------------- 2025-12-14T11:49:07 | u | 300.0*2 | >22.68 2025-12-14T11:31:54 | v | 300.0*2 | >22.47 2025-12-14T11:49:09 | g | 300.0*2 | 21.08 (+/-0.12) 2025-12-14T11:31:56 | r | 300.0*2 | 20.64 (+/-0.08) 2025-12-14T11:49:09 | i | 300.0 | 19.50 (+/-0.07) 2025-12-14T11:31:56 | z | 300.0 | 18.60 (+/-0.14) The optical detection of the burst is consistent with Eyles-Ferris et al. 2025 (GCN 43089); Kang et al. 2025 (GCN 43093); Gress et al. 2025 (GCN 43095); Fu et al. 2025 (GCN 43097); Gupta et al. 2025 (GCN 43100); Watson et al. (GCN 43103); Kuin et al. (GCN 43105); Pérez-Fournon (GCN 43123); Volnova et al. (GCN 43124); Postigo et al. (GCN 43131). ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025, and these are currently in the commissioning phase. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/43134. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41215] GRB 251215A: Glowbug gamma-ray detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43133 SUBJECT: GRB 251215A: Glowbug gamma-ray detection DATE: 25/12/15 23:10:15 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251215A, which was also detected by Fermi/GBM (GCN 43104), Swift/BAT-GUANO (GCN 43114), and CALET (trigger 1449807236). Glowbug was in the SAA at the time of the GBM T0 (04:21:21) and recorded data beginning at T0+20s, initially with high background rates as it was exiting the SAA. Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-12-15 04:22:25.800 with a duration of 76.0 s and a total significance of about 23.8 sigma. The burst originated toward the Nadir side of Glowbug and was detected despite passing through the passive material from the H9 pallet and internal passive material/shielding within Glowbug. The Glowbug onset is 64.8 s after the GBM T0, and the Glowbug light curve comprises three peaks at ~T0+1s, ~T0+25s, and ~T0+72s; the T0+72s peak matches the CALET trigger time (04:23:36.282). The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43133. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41214] GRB 251214B: UAFO optical upper limit
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43132 SUBJECT: GRB 251214B: UAFO optical upper limit DATE: 25/12/15 18:11:38 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> N. S. Pankov (HSE, IKI), A. Kochergin (UAFO IAA), A. A. Volnova (IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112; Laha et al., GCN 43129), and GECAM-B (Luo et al., GCN 43113) with the RC-500 (0.5m) telescope of Ussuriysk Astrophysical Observatory (UAFO) taking several frames in R-band. The observations started on Dec. 14 at 10:44 UT, i.e., ~ 1.5 hours after the Swift/BAT trigger. In the stacked image we do not detect the optical counterpart reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123; Volnova et al., GCN 43124; de Ugarte Postigo et al., GCN 43131). Photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-14 10:44:26 0.09073 57*60 R n/d n/d 19.4 UAFO/RC500 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43132. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41213] GRB 251214B: VLT/X-shooter observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43131 SUBJECT: GRB 251214B: VLT/X-shooter observations DATE: 25/12/15 17:56:34 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), M. Garnichey (LUX-Paris Obs.), J. An (NAOC), G. Corcoran (UCD), L. Izzo (INAF/OACn & DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF/IAPS), A. Torralba (ISTA) and Y. Ma (Princeton U.) report on behalf of the Stargate collaboration: We observed the optical counterpart of GRB 251214B detected by Fermi (Fermi GBM team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089) and GECAM-B (Luo et al., GCN 43113) with X-shooter mounted on the UT3 (Melipal) of ESO’s Very Large Telescope (Paranal Observatory, Chile). Observations were conducted in twilight and at large airmass. The acquisition images, which started at 00:46:54 UT of 15 Dec 2025 (15.74 hr after the burst onset) show the counterpart with the following photometry (AB magnitudes), as compared to field stars from the SDSS catalogue: g = 23.15 +/- 0.06 r = 22.19 +/- 0.04 z = 20.76 +/- 0.05 A 2x600 s spectrum followed, covering the spectral range between 3000 and 21000 AA. The spectrum shows a red continuum, consistent with the photometry, only detectable above 6000 AA, and more prominent at infrared wavelengths. We do not detect clear emission features from the underlying host galaxy (mentioned by Gress et al., GCN 43095 and Watson et al., GCN 43103), which prevents us from measuring its redshift. We note that the Legacy Survey reveals that the source underlying the afterglow is composed of two blobs, a fainter one right under the GRB and a brighter one towards the North East, at a distance of 1". The slight difference between our photometry and the one of COLIBRÍ (Watson et al., GCN 43103) could be due to the different contribution of these underlying sources within the photometric aperture. We acknowledge expert support from the ESO observing staff in Paranal, in particular Claudia Paladini, Célia Desgrange, Cecila Bustos, and Ana Jimenez-Gallardo. View this GCN Circular online at https://gcn.nasa.gov/circulars/43131. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41212] GRB 251213A: GRID-10B observation
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43130 SUBJECT: GRB 251213A: GRID-10B observation DATE: 25/12/15 16:43:28 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Xiao-Fan Pan, Long-Hao Li, Chen-Yu Wang, Zi-Rui Yang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 251213A, a long-duration gamma-ray burst. The event triggered GRID-10B at T0 = 2025-12-13 12:30:04 UTC. The measured burst duration (10B) is T90 = 35.5 ± 3.2 s in the 30–2000 keV energy range. The event was also detected by GRID-11B (GCN #43116), GECAM-B (GCN #43106), SVOM/GRM (GCN $43111), and AstroSat CZTI (GCN #43108). The GRID light curves for this event are available at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB251213A/GRID_GRB…. GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43130. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41211] GRB 251214B: Swift-BAT refined analysis
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43129 SUBJECT: GRB 251214B: Swift-BAT refined analysis DATE: 25/12/15 16:41:36 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), R. A. J. Eyles-Ferris (U Leicester), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251214B (trigger #1423875) (Eyles-Ferris, et al., GCN Circ. 43089). The BAT ground-calculated position is RA, Dec = 330.222, -9.155 deg which is RA(J2000) = 22h 00m 53.4s Dec(J2000) = -09d 09' 17.3" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted BAT light curve shows a double-peaked structure with a duration of about 10 sec T90 (15-350 keV) is 9.38 +- 0.73 sec (estimated error including systematics). The time-averaged spectrum from T-0.19 to T+9.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.12. The fluence in the 15-150 keV band is 5.0 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.13 sec in the 15-150 keV band is 2.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1423875 View this GCN Circular online at https://gcn.nasa.gov/circulars/43129. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41210] GRB 251202A: radio detection with the VLA
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43128 SUBJECT: GRB 251202A: radio detection with the VLA DATE: 25/12/15 16:38:56 GMT FROM: Stefano Giarratana at INAF-OAB <s.giarratana(a)ira.inaf.it> S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB), L. Nava (INAF-OAB) At 12:00:00 UT on 2025 December 5 (T_mid = 3.45 days post-burst) the Karl G. Jansky VLA observed the field of GRB 251202A / EP251202A (Fermi GBM team, GCN 42933, 42957; Einstein Probe team, GCN 42937, GCN 42946; AstroSat CZTI collaboration, GCN 42967; Insight-HXMT team, GCN 42970; SVOM team, GCN 42997) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass and flux density calibrator, while J0818+4222 was used as phase calibrator. From a preliminary analysis, an unresolved radio source is detected at a position (J2000): RA: 08:08:27.466 +- 0.001 Dec: +40:36:44.70 +- 0.01 consistent with the X-ray (Einstein Probe team, GCN 42937; Swift-XRT team, GCN 42943) and optical (GOTO collaboration, GCN 42947; Quirola-Vasquez, GCN 42948; Swift/UVOT team, GCN 42956; KAIT GRB team, GCN 42964; SVOM/VT team, GCN 42966; Bochenek et al., GCN 42977; Contreras et al., GCN 42999) position of the transient. The preliminary analysis yields the following results: ================================================================ T_mid Freq Peak r.m.s. Beam PA [days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg] ================================================================ 3.45 6 111 10 1.08x1.02 57 3.45 10 169 7 0.71x0.60 59 3.45 15 310 8 0.45x0.42 34 ================================================================ No source is detected with a >3sigma confidence level at the aforementioned position in the VLASS. However, the r.m.s. noise level of the survey at the GRB location is approximately 130 uJy/b. We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF181027, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/43128. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41209] EP251214b: Global MASTER-Net observations report
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43127 SUBJECT: EP251214b: Global MASTER-Net observations report DATE: 25/12/15 16:09:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251214b ( EP Team et al., GCN 43125) errorbox 1777 sec after trigger time at 2025-12-14 07:49:59 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 14 deg. The sun altitude is -17.5 deg. The galactic latitude b = 22 deg., longitude l = 256 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3071744 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1807 | 2025-12-14 07:49:59 | MASTER-OAFA | (09h 37m 50.45s , -22d 35m 38.5s) | C | 60 | 20.5 | 1873 | 2025-12-14 07:51:04 | MASTER-OAFA | (09h 37m 50.56s , -22d 35m 35.8s) | C | 60 | 20.5 | 1939 | 2025-12-14 07:52:10 | MASTER-OAFA | (09h 37m 50.68s , -22d 35m 33.3s) | C | 60 | 20.5 | 2004 | 2025-12-14 07:53:16 | MASTER-OAFA | (09h 37m 50.79s , -22d 35m 30.8s) | C | 60 | 20.4 | 2070 | 2025-12-14 07:54:22 | MASTER-OAFA | (09h 37m 50.91s , -22d 35m 28.4s) | C | 60 | 20.4 | 2137 | 2025-12-14 07:55:28 | MASTER-OAFA | (09h 37m 51.00s , -22d 35m 26.1s) | C | 60 | 20.5 | 2202 | 2025-12-14 07:56:34 | MASTER-OAFA | (09h 37m 51.12s , -22d 35m 23.9s) | C | 60 | 20.4 | 2268 | 2025-12-14 07:57:39 | MASTER-OAFA | (09h 37m 51.21s , -22d 35m 21.8s) | C | 60 | 20.5 | 2334 | 2025-12-14 07:58:45 | MASTER-OAFA | (09h 37m 51.29s , -22d 35m 19.7s) | C | 60 | 20.5 | 2399 | 2025-12-14 07:59:51 | MASTER-OAFA | (09h 37m 51.36s , -22d 35m 17.2s) | C | 60 | 20.4 | 2465 | 2025-12-14 08:00:57 | MASTER-OAFA | (09h 37m 51.42s , -22d 35m 15.1s) | C | 60 | 20.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43127. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41208] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43126 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:57:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43126. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41207] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43125 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:56:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41206] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43125 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:56:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41205] GRB 251214B: AbAO optical observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43124 SUBJECT: GRB 251214B: AbAO optical observations DATE: 25/12/15 14:54:17 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), R. Ya. Inasaridze (AbAO), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112), and GECAM-B (Luo et al., GCN 43113) with the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. The observations started on Dec. 14 at 15:00 UT, i.e., ~ 6 hours after the Swift/BAT trigger. In the stacked image we detect the optical afterglow reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123). Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-14 15:00:25 0.27325 51*60 R 20.6 0.2 20.7 AbAO/AS-32 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41204] GRB 251214B: LCO detection of the optical counterpart
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43123 SUBJECT: GRB 251214B: LCO detection of the optical counterpart DATE: 25/12/15 14:21:49 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL) Following the detection of the long GRB 251214B, detected by Fermi GBM (Fermi GBM team, GCN #43088), Swift BAT, XRT, and UVOT (Eyles-Ferris et al., GCN #43089; Evans et al., GCN #43098; Kuin and Eyles-Ferris, GCN #43105; and Burrows et al., GCN #43112), and GECAM-B (Luo et al., GCN #43113), we observed the field with one of the two Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Siding Spring Observatory near Coonabarabran, New South Wales, Australia. The observation, a single exposure of 60 sec in the SDSS r' filter, started on 2025-12-14 at 10:26:57 UT, about 1.41 hours after the Fermi, Swift, and GECAM-B triggers. The optical counterpart first detected by Swift UVOT (Eyles-Ferris et al., GCN #43089) is clearly detected in our image with a preliminary magnitude of r' = 19.18 +/- 0.10, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical and UV detections (Eyles-Ferris et al., GCN 43089; Kang et al., GCN #43093; Gress et al., GCN #43095; Fu et al., GCN #43097; Gupta et al., GCN #43100; Watson et al., GCN #43103; and Kuin and Eyles-Ferris, GCN #43105). Our preliminary photometry is not corrected for the light of the likely host galaxy discussed by Gress et al. (GCN #43095), and Watson et al. (GCN #43103) at a photometric redshift of z = 0.709 +/- 0.078 (Duncan, 2022). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-008, SGLF and Superluminous Supernovae surveys). This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5). View this GCN Circular online at https://gcn.nasa.gov/circulars/43123. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41203] GRB 251209A: GECAM-B observation of a long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43122 SUBJECT: GRB 251209A: GECAM-B observation of a long burst DATE: 25/12/15 13:57:46 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Sheng-Lun Xie, Yang-Zhao Ren, Peng Zhang, Yue Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst GRB 251209A at 2025-12-09T13:24:22.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43048 and GCN #43068), Global MASTER-Net (V.Lipunov et al., GCN#43053), AstroSat CZTI (M. Tembhurnikar et al., GCN#42996), NuSTAR (G. Waratkar et al., GCN #43078) and Insight-HXMT (Hao-Xuan Guo et al., GCN #43119). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses main emission with a duration (T90) of 40.5 +/-1.7 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb251209A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43122. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41202] GRB 251214D: GECAM-B observation of a long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43121 SUBJECT: GRB 251214D: GECAM-B observation of a long burst DATE: 25/12/15 13:47:03 GMT FROM: Xinghao Luo at SVOM/GRM <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 251214D, at 2025-12-14T21:24:17.950 UTC (denoted as T0), which is also detected by AstroSat/CZTI (A. Arya et.al., GCN #43109). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 28.5 +6.5/-5.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251214D.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43121. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41201] GRB 251214B: Fermi GBM Observation
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43120 SUBJECT: GRB 251214B: Fermi GBM Observation DATE: 25/12/15 13:26:50 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova (MUNI) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 09:02:18.03 UT on 14 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214B (trigger 787395743/251214377), which was also detected by Swift BAT (R. A. J. Eyles-Ferris et al. 2025, GCN 43089) and GECAM-B (X. H. Luo et al. 2025, GCN 43113). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 97 degrees. The GBM light curve consists of a double-peaked emission with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-0.6 to T0+9.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.81 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1280 +/- 80 keV. The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.58 s in the 10-1000 keV band is 3.3 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41200] GRB 251209A: Insight-HXMT/HE detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43119 SUBJECT: GRB 251209A: Insight-HXMT/HE detection DATE: 25/12/15 13:24:01 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-09T13:24:31.000 (T0), Insight-HXMT/HE detected a long burst, GRB 251209A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43048 and GCN #43068), Global MASTER-Net (V.Lipunov et al., GCN#43053), AstroSat CZTI (M. Tembhurnikar et al., GCN#42996) and NuSTAR (G. Waratkar et al., GCN #43078). The Insight-HXMT/HE light curve mainly consists of multiple pulses with T90 of 43.0 +13.5/-10.0 s. The 1s peak rate, measured from T0+0.25 s, is 822 cnts/sec. Insight-HXMT/HE detected a total of 12,343 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251209A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Low-Gain mode with the energy range of about 300-3000 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org View this GCN Circular online at https://gcn.nasa.gov/circulars/43119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41199] GRB 251215A: Swift ToO observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43118 SUBJECT: GRB 251215A: Swift ToO observations DATE: 25/12/15 13:10:55 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Swift/BAT-detected event GRB 251215A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021894 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41198] EP trigger 01709250023: LCO optical limits
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43117 SUBJECT: EP trigger 01709250023: LCO optical limits DATE: 25/12/15 12:43:14 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the EP/EXT trigger 01709250023 (trigger time 2025-12-14T07:20:22.899 UT), using the Sinistro instrument at the 1m telescope in Siding Springs, Australia, part of the LCO network. Observations were carried out in the r (3x300 s) and z (6x300 s) bands, at mean epochs of 2025 Dec 14.658 and 14.687 UT, respectively (8.395 and 9.076 hr after trigger). After subtracting from our stacks archival templates from the Pan-STARRS survey, we detect no new sources in either bands within the EP/WXT error circle, down to 3-sigma limiting AB magnitudes r > 22.4 and z > 21.6 (photometry calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction). The two sources detected by Swift/XRT outside the EP/WXT error circle (https://www.swift.ac.uk/EP/EP_FIELD00087/) have stellar counterparts in Pan-STARRS. This further confirms that they are unlikely to be related to the EP transient. Furthermore, XRT source #1 matches an AGN from the C75 WISE AGN catalog (Assef et al. 2018; doi:10.3847/1538-4365/aaa00a), and is thus possibly an AGN. The lack of detection is consistent with the results by COLIBRÍ (Basa et al., GCN 43090) and Swift/XRT. View this GCN Circular online at https://gcn.nasa.gov/circulars/43117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41197] GRID detection of GRB 251213A
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43116 SUBJECT: GRID detection of GRB 251213A DATE: 25/12/15 11:47:12 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Long-Hao Li, Chen-Yu Wang, Zi-Rui Yang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 251213A, a long-duration gamma-ray burst, which was also detected by GECAM-B (GCN Circ.43106), SVOM/GRM and AstroSat CZTI (GCN Circ. 43108). The event triggered GRID-11B at T0 = 2025-12-13 12:30:04 UTC. The measured burst duration is T90 = 34.6 ± 2.8 s in the 30–2000 keV energy range. The GRID light curve for this event is available at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB251213A/GRID_GRB…. GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41196] GRB 251203B: AbAO optical observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43115 SUBJECT: GRB 251203B: AbAO optical observations DATE: 25/12/15 11:12:25 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), R. Ya. Inasaridze (AbAO), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the SWOM trigger sb25120304 (Brunet et al. GCN 42973) with the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. The observations started on Dec. 3 at 21:00 UT, i.e., ~ 3 hours after the SWOM trigger. In the stacked image, we do not detect any new source within the MXT error circle. The star Gaia DR3 2534635509050352256 reported previously (Palmerio et al., GCB 42978; Malesani et al., GCN 42979; Perez-Garcia et al., GCN 42982) is consistent with two USNO-B1.0 sources 0900-0013627 (RA(J2000) = 01:13:26.6548920, Dec(J2000) = +00:01:08.382180; R1 = 13.31) and 0900-0013628 (RA(J2000) = 01:13:26.8108752, Dec(J2000) = +00:01:08.040144; R2 = 13.83) and is clearly detected in the stacked frame. Its R-magnitude is brighter ~0.2 mag than the catalogue USNO-B1.0 R1 value, that supports the nature of the trigger as a star flare. Photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-03 21:00:00 0.15311 60*20 R 13.13 0.02 19.5 AbAO/AS-32 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43115. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41195] GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43114 SUBJECT: GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst DATE: 25/12/15 10:28:41 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (GSSI), James DeLaunay (PSU), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251215A onboard (T0: 2025-12-15T04:21:21.57 UTC, Fermi GCN 43104). The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The position is found with the newly developed pipeline BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs (Ronchini et. al, in prep). The pipeline makes use of the tools from BatAnalysis ([Parsotan et al. 2025](https://iopscience.iop.org/article/10.3847/1538-4357/ade240)) The source was detected with an SNR = 6.5 in a 16.384 s analysis time bin starting at t0 - 4.096 s. Independently, the BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), confirms the detection of the burst in a 16.384 s analysis time bin starting at T0 - 4.096 s with a sqrt(TS) of 14.6. An arcminute localization is found with DeltaLLHOut of 63.97 and a DeltaLLHPeak of 36.66. See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. The NITRATES and BAT-GLIMPSE positions are compatible. Moreover, at T0: 2025-12-15T04:23:36.28 UTC, also a CALET trigger (trig number 1449807236) activated GUANO. A signal is found by BAT-GLIMPSE during Swift slew using a mosaic technique. The source is found with an SNR = 27.1. The position is compatible with the one found by BAT-GLIMPSE and NITRATES for the Fermi-GBM trigger. Hence we conclude that the two signals are associated to the same GRB. The BAT position is: RA, Dec = 122.6526, -36.7395 deg which is RA(J2000) = 08h 10m 36.62s Dec(J2000) = -36d 44’ 22.2″ with an estimated uncertainty of 3 arcmin radius. More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=787465318 XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43114. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41194] GRB 251214B: GECAM-B observation of a long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43113 SUBJECT: GRB 251214B: GECAM-B observation of a long burst DATE: 25/12/15 09:50:28 GMT FROM: Xinghao Luo at SVOM/GRN <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 251214B, at 2025-12-14T09:02:19.10 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43088). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 17.7 +1.8/-1.2 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251214B.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43113. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41193] GRB 251214B: Swift-XRT refined Analysis
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43112 SUBJECT: GRB 251214B: Swift-XRT refined Analysis DATE: 25/12/15 09:28:13 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.9 ks of XRT data for GRB 251214B, from 46 s to 28.7 ks after the trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with an initial power-law decay with an index of alpha=0.72 (+0.14, -0.17), followed by a break at T+418 s to an alpha of 1.33 (+0.10, -0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.82 (+0.19, -0.18). The best-fitting absorption column is 1.6 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 4.0 x 10^20 cm^-2 Excess significance: 3.5 sigma Photon index: 1.82 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 1.33, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.3 x 10^-14 (7.8 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01423875. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43112. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41192] GRB 251213A: SVOM/GRM observation
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43111 SUBJECT: GRB 251213A: SVOM/GRM observation DATE: 25/12/15 09:24:16 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 251213A (SVOM trigger reference: sb25121302) at 2025-12-13T12:30:05.000 UTC (T0), which is also detected by GRID, GECAM-B (Wang et al., GCN#43106) and AstroSat (Harsha K. H. et al., GCN#43108). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 36.5 +1.0/-1.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251213A.png In addition, the position of this burst, as determined by GECAM-B (RA= 296.5, DEC= -11.9, ERR=5.6), is located at about 102 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-5 to T0+45 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.95 +0.10/-0.09 and the cutoff energy, parameterized as Epeak, is 453 +63/-50 keV. The event fluence (10-1000 keV) in this time interval is (5.58 +0.18/-0.19)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+5.0 to T0+6.0 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.09 +0.14/-0.12 and the cutoff energy, parameterized as Epeak, is 800 +286/-182 keV. The flux (10-1000 keV) in this time interval is (3.31 +0.13/-0.14)E-06 erg/cm^2/s. The localization of GRB 251213A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251213A_amati.png And the localization in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251213A_yonetoku.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43111. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41191] EP251214a: KAIT optical upper limit
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43110 SUBJECT: EP251214a: KAIT optical upper limit DATE: 25/12/15 07:28:01 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP251214a (Yin et al., GCN 43087; 43102) starting at 08:58, Dec 14 UT, about 6.52 hours after the burst. A set of 129x60s clear (roughly R) filter images were obtained. In our coadd image, we did not detect any new source within the EP-WXT error circle (Yin et al., GCN 43087) down to a limiting mag of 21.6 mag (Vega) at a mid-time of 8.88 hours after the burst. Our result is consistent with the upper limit reported by other groups (Basa et al., GCN 43092; Lipunov et al., GCN 43099). View this GCN Circular online at https://gcn.nasa.gov/circulars/43110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41190] GRB 251214D: AstroSat CZTI detection of a long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43109 SUBJECT: GRB 251214D: AstroSat CZTI detection of a long burst DATE: 25/12/15 06:49:33 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 251214D. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-14 21:24:21.50 UTC. The measured peak count rate associated with the burst is 71 (+34, -11) counts/s above the background in the combined data of all quadrants, with a total of 576 (+192, -210) counts. The local mean background count rate was 264 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 16 (+3, -7) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-14 21:24:21.75 UTC. The measured peak count rate associated with the burst is 231 (+68, -36) counts/s above the background in the combined data of all quadrants, with a total of 1844 (+413, -469) counts. The local mean background count rate was 1211 (+7, -7) counts/s. We measure a T90 of 20 (+2, -8) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43109. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41189] GRB 251213A: AstroSat CZTI detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43108 SUBJECT: GRB 251213A: AstroSat CZTI detection DATE: 25/12/15 06:37:41 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 251213A which was also detected by GECAM-B (Wang et. al., GCN Circ. 43106). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-13 12:30:11.00 UTC. The measured peak count rate associated with the burst is 48 (+18, -9) counts/s above the background in the combined data of three quadrants (out of four), with a total of 617 (+188, -211) counts. The local mean background count rate was 187 (+1, -2) counts/s. Using cumulative rates, we measure a T90 of 39 (+1, -14) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-13 12:30:12.01 UTC. The measured peak count rate associated with the burst is 265 (+71, -15) counts/s above the background in the combined data of all quadrants, with a total of 3624 (+653, -519) counts. The local mean background count rate was 1137 (+4, -6) counts/s. We measure a T90 of 36 (+1, -2) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41188] GRB 251214A: AstroSat CZTI detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43107 SUBJECT: GRB 251214A: AstroSat CZTI detection DATE: 25/12/15 06:13:10 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> A. Goyal (IITB), A. Arya (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251214A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43086). We detect only the brighter shorter-duration part of the burst as seen in the GBM lightcurve because the source location was at an angle of 110 deg from the pointing axis of AstroSat CZTI. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-14 00:11:15.25 UTC. The measured peak count rate associated with the burst is 274 (+153, -45) counts/s above the background in the combined data of all quadrants, with a total of 134 (+124, -33) counts. The local mean background count rate was 269 (+5, -23) counts/s. Using cumulative rates, we measure a T90 of 1.4 (+0.2, -1.0) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-14 00:11:14.91 UTC. The measured peak count rate associated with the burst is 347 (+66, -71) counts/s above the background in the combined data of all quadrants, with a total of 418 (+226, -230) counts. The local mean background count rate was 1283 (+6, -7) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 for our detection. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43107. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41187] GRB 251213A: GECAM-B detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43106 SUBJECT: GRB 251213A: GECAM-B detection DATE: 25/12/15 06:05:28 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 251213A, at 2025-12-13T12:30:05.050 UTC (denoted as T0), which is also detected by SVOM/GRM and GRID. According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a precursor followed by multi-pulses with a duration (T90) of 34.6 +1.0/-1.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251213A.png GECAM-B localized this burst to the following position (J2000): Ra: 296.5 deg Dec: -11.9 deg Err: 5.6 deg (1-sigma, statistical only) We note that the non-detection by Fermi/GBM suggests that the error box can be further constrained in the future. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43106. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41186] GRB 251214B: Swift/UVOT Detection
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43105 SUBJECT: GRB 251214B: Swift/UVOT Detection DATE: 25/12/15 05:01:50 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (MSSL/UCL) and R. Eyles-Ferris (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251214B 64 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 43089). A source consistent with the XRT position Evans et al. GCN Circ. 43098) is detected in the initial UVOT exposures. There were early reports of the optical afterglow from Zhe Kang et al. (GCN Circ. 43093) and S.Y. Fu et al. (GCN Circ. 43097). The preliminary UVOT position is: RA (J2000) = 22:00:50.53 = 330.21053 (deg.) Dec (J2000) = -09:09:46.4 = -9.16290 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 64 214 147 17.21 +/- 0.03 v 606 800 39 17.09 +/- 0.17 b 532 724 39 18.08 +/- 0.17 u 277 527 246 17.76 +/- 0.08 w1 655 1472 97 >18.9 m2 630 1447 97 >20.3 w2 582 5213 136 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41185] GRB 251215A: Fermi GBM Final Real-time Localization
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43104 SUBJECT: GRB 251215A: Fermi GBM Final Real-time Localization DATE: 25/12/15 04:31:53 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 04:21:21 UT on 15 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251215A (trigger 787465286.567966 / 251215181). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 112.8, Dec = -43.7 (J2000 degrees, equivalent to J2000 07h 31m, -43d 42'), with a statistical uncertainty of 7.6 degrees. The angle from the Fermi LAT boresight is 31.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251215181/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43104. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41184] GRB 251214B: COLIBRÍ observations of the afterglow
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43103 SUBJECT: GRB 251214B: COLIBRÍ observations of the afterglow DATE: 25/12/15 04:27:56 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), Camila Angulo (UNAM), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Fermi/Swift GRB 251214B (Fermi GBM Team, GCN Circ. 43088; Eyles-Ferris et al., GCN Circ. 43089) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-15 01:33 to 03:22 UTC (from 16.52 to 18.34 hours after the Swift/BAT trigger) and obtained 28, 28, 28, and 84 minutes of simultaneous exposure in the g, r, i, and z filters, respectively. The data were reduced, coadded, and analyzed with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In our stacked images, at the position of the afterglow (Eyles-Ferris et al., GCN Circ. 43089; Kang et al., GCN Circ. 43093; Gress et al., GCN Circ. 43095; Fu et al., GCN Circ. 43097; and Gupta et al., GCN Circ 43100) we detect the a source with preliminary magnitudes of: g = 22.97 +/- 0.21 r = 22.05 +/- 0.12 i = 21.52 +/- 0.12 z = 20.97 +/- 0.08 We note the presence of a bright galaxy coincident with the afterglow in Legacy Survey observations (Dey et al. 2019) with g = 23.70 +/- 0.11, r = 22.37 +/- 0.06, i = 21.62 +/- 0.06, z = 21.12 +/- 0.04, and a photometric redshift of z = 0.70 +/- 0.07. We suggest this might be the host galaxy. Its low redshift is consistent with the detection of the afterglow in g by Kang et al. (GCN Circ. 43093) and in our observations. Our observations include light from both the afterglow and this galaxy, and the afterglow is only clearly detected above the galaxy in g. The fading in g between the observations of Kang et al. (GCN Circ. 43093) and our observations implies a temporal power-law index of 1.08 or steeper. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43103. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41183] EP251214a: EP-FXT non-detection and upper limit
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43102 SUBJECT: EP251214a: EP-FXT non-detection and upper limit DATE: 25/12/15 02:22:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), Y. H. Jiang (NJU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: EP-FXT observed the field of EP251214a (Yin et al., GCN 43087) for 2997 seconds starting at 2025-12-14T15:14:34, around 13 hours after the detection by EP-WXT. No significant X-ray source is detected within the 3.1 arcmin radius of the EP-WXT position (Yin et al., GCN 43087) to a preliminary 0.5-10 keV upper limit of 7e-14 erg/cm2/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41182] GRB 251208C: GECAM-B observation of a likely long burst
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43101 SUBJECT: GRB 251208C: GECAM-B observation of a likely long burst DATE: 25/12/15 01:08:35 GMT FROM: Xinghao Luo at SVOM/GRN <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 251214A, at 2025-12-14T00:11:15.200 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43085). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 5.0 +1.0/-2.5s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251214A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/43101. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41181] GRB 251214B: 1.3m DFOT optical detection
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43100 SUBJECT: GRB 251214B: 1.3m DFOT optical detection DATE: 25/12/14 20:36:58 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina Kar, and Kuntal Misra (ARIES) report: We observed the field of GRB 251214B detected by Fermi/GBM (Fermi GBM team, GCN 43088) and Swift/BAT (Eyles-Ferris et al. 2025, GCN 43089) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-12-14 at 12:59:37 UT, i.e., ~ 3.95 hours after the Fermi/GBM trigger. We have taken multiple frames with an exposure time of 300s in the I filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image within the error box of Swift/UVOT (Eyles-Ferris et al. 2025, GCN 43089). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude =============================================================== 2025-12-14 12:59:37 ~3.95 I 300s*18 20.03 +/-0.03 The optical detection of the burst is consistent with Eyles-Ferris et al. 2025 (GCN 43089); Lipunov et al. 2025 (GCN 43091); Kang et al. 2025 (GCN 43093); Gress et al. 2025 (GCN 43095); and Fu et al. 2025 (GCN 43097). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43100. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41180] EP251214a: Global MASTER-Net observations report
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43099 SUBJECT: EP251214a: Global MASTER-Net observations report DATE: 25/12/14 19:09:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP251214a ( EP Team et al., GCN 43087) errorbox 23345 sec after notice time and 44450 sec after trigger time at 2025-12-14 14:47:51 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 80 deg. The sun altitude is -52.2 deg. The galactic latitude b = 50 deg., longitude l = 212 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070739 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 11367 | 2025-12-14 05:35:57 | MASTER- | (09h 49m 46.34s , +21d 15m 33.3s) | C | 60 | 17.1 | 12140 | 2025-12-14 05:48:51 | MASTER- | (09h 47m 03.54s , +20d 23m 17.9s) | C | 60 | 18.1 | 12140 | 2025-12-14 05:48:51 | MASTER- | (09h 58m 23.13s , +19d 21m 03.2s) | C | 60 | 17.0 | 12427 | 2025-12-14 05:53:37 | MASTER- | (09h 54m 39.28s , +22d 17m 23.3s) | C | 60 | 18.4 | 28176 | 2025-12-14 10:15:06 | MASTER- | (09h 45m 41.72s , +21d 23m 05.5s) | C | 180 | 19.6 | 28176 | 2025-12-14 10:15:06 | MASTER- | (09h 57m 15.83s , +20d 21m 58.5s) | C | 180 | 19.3 | 44480 | 2025-12-14 14:47:51 | MASTER-Tunka | (09h 53m 14.05s , +20d 49m 09.6s) | C | 60 | 18.4 | 57811 | 2025-12-14 18:30:01 | MASTER-Tunka | (09h 50m 07.21s , +22d 38m 41.9s) | C | 60 | 20.0 | 57812 | 2025-12-14 18:30:02 | MASTER-Tunka | (09h 49m 36.25s , +22d 46m 24.5s) | C | 60 | 19.6 | 59105 | 2025-12-14 18:51:35 | MASTER-Tunka | (09h 58m 44.22s , +20d 43m 39.4s) | C | 60 | 19.6 | 59105 | 2025-12-14 18:51:35 | MASTER-Tunka | (09h 58m 13.62s , +20d 51m 19.9s) | C | 60 | 19.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43099. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41179] GRB 251214B: Enhanced Swift-XRT position
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43098 SUBJECT: GRB 251214B: Enhanced Swift-XRT position DATE: 25/12/14 17:09:40 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1446 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251214B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 330.21069, -9.16291 which is equivalent to: RA (J2000): 22h 00m 50.57s Dec (J2000): -09d 09' 46.5" with an uncertainty of 2.1 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at https://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43098. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41178] GRB 251214B: Xinglong-2.16m optical observation
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43097 SUBJECT: GRB 251214B: Xinglong-2.16m optical observation DATE: 25/12/14 13:15:50 GMT FROM: syfu(a)nao.cas.cn S.Y. Fu(HUST), D. Xu, Y.N. Zhu, P.L. Du, J.J. Jin, Z. Fan, X. Liu, L.B. He, J. An, S.Q. Jiang, Z.P. Zhu, J.J. Jia(NAOC) We observed the field of GRB 251214B detected by Swift (Eyles-Ferris et al., GCN 43089) using the Xinglong-2.16m telescope equipped with the BFOSC camera. Observations started at 10:26:38 UT on 2025-12-14 (i.e., 1.41 h after the trigger), and a series of r- / g-band frames have been obtained. The optical afterglow (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095) was clearly detected in our stacked frame with a magnitude of r = 19.40 +- 0.03 at a mid-time of 1.53 hr and g = 20.63 +- 0.09 at a mid-time of 1.88 hr, respectively, calibrated with Pan-STARRS1 DR2 catalog and not corrected for Galactic extinction. We thank the staff at Xinglong observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43097. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41177] GRB 251214C: Fermi GBM Final Localization
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43096 SUBJECT: GRB 251214C: Fermi GBM Final Localization DATE: 25/12/14 13:08:43 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> The Fermi GBM team reports the detection of a likely LONG GRB "At 09:17:32.51 UT on 14 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214C (trigger 787396657/251214387). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 346.3, Dec = 41.0 (J2000 degrees, equivalent to J2000 23h 05m, +41d 0'), with a statistical uncertainty of 6.0 degrees. The angle from the Fermi LAT boresight is 138 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214387/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214387/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214387/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43096. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41176] GRB 251214B : MASTER optical afterglow detection
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43095 SUBJECT: GRB 251214B : MASTER optical afterglow detection DATE: 25/12/14 12:55:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> O.A.Gress, N.M.Budnev (ISU), V.M.Lipunov, P.Balanutsa, I.Panchenko, A.Kuznetsov, E.Gorbovskoy, G.Antipov, N. Tiurina, Ya.Kechin,A.Chasovnikov, D.Vlasenko, V.Shumkov, I.Ionov, Yu.Tselik(Lomonosov MSU, SAI, Moscow), R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain) MASTER OT J220050.55-090945.8 detection MASTER-Tunka robotic telescope of MASTER Global Robotic Net (Lipunov et al. [1-4], http://observ.pereplet.ru ), started Fermi (GCN 43088) and Swift (GCN 43089) GRB 251214B error-box observations after sunset at 2025-12-14 10:20:46 UT (Lipunov et al. GCN 43091, cover map https://master.sai.msu.ru/site/master2/event.php?id=3070779 ) MASTER auto-detection system found optical afterglow at summary images MASTER OT J220050.55-090945.8 , discovered by Swift (Eyles-Ferris et al. GCN 430089) and also observed by SVOM (Zhe Kang et al. GCN 43093) with unfiltered m_OT=19.5m at 2025-12-14 10:49:16UT. There is SDSS galaxy (poss.host) in 0.067" in VIZIER database with z_phot=0.6634 Observation and reduction will continue. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/43095. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41175] Fermi trigger No 787396657: Global MASTER-Net observations report
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43094 SUBJECT: Fermi trigger No 787396657: Global MASTER-Net observations report DATE: 25/12/14 12:15:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB251214.39 (trigger No 787396657,23h 11m 00.00s , +35d 42m 36.0s, R=7.23) errorbox 7860 sec after notice time and 7881 sec after trigger time at 2025-12-14 11:28:54 UT, with upper limit up to 19.8 mag. The observations began at zenith distance = 17 deg. The sun altitude is -22.1 deg. The galactic latitude b = -23 deg., longitude l = 102 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070847 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 7911 | 2025-12-14 11:28:54 | MASTER-Tunka | (23h 18m 11.56s , +35d 35m 58.5s) | C | 60 | 19.8 | 7912 | 2025-12-14 11:28:54 | MASTER-Tunka | (23h 17m 27.54s , +35d 43m 36.3s) | C | 60 | 19.4 | 7984 | 2025-12-14 11:30:06 | MASTER-Tunka | (22h 59m 36.09s , +35d 37m 15.6s) | C | 60 | 19.8 | 7984 | 2025-12-14 11:30:06 | MASTER-Tunka | (22h 58m 52.22s , +35d 44m 52.1s) | C | 60 | 19.5 | 8057 | 2025-12-14 11:31:19 | MASTER-Tunka | (23h 04m 12.06s , +33d 49m 52.3s) | C | 60 | 19.4 | 8057 | 2025-12-14 11:31:19 | MASTER-Tunka | (23h 04m 54.44s , +33d 42m 21.6s) | C | 60 | 19.8 | 8131 | 2025-12-14 11:32:33 | MASTER-Tunka | (23h 14m 26.42s , +37d 31m 33.7s) | C | 60 | 19.7 | 8131 | 2025-12-14 11:32:33 | MASTER-Tunka | (23h 13m 40.85s , +37d 39m 18.2s) | C | 60 | 19.3 | 8206 | 2025-12-14 11:33:48 | MASTER-Tunka | (22h 55m 29.62s , +37d 30m 10.5s) | C | 60 | 19.5 | 8206 | 2025-12-14 11:33:48 | MASTER-Tunka | (22h 54m 44.15s , +37d 37m 53.0s) | C | 60 | 19.1 | 8284 | 2025-12-14 11:35:06 | MASTER-Tunka | (23h 23m 04.59s , +33d 41m 38.5s) | C | 60 | 19.3 | 8284 | 2025-12-14 11:35:06 | MASTER-Tunka | (23h 22m 22.17s , +33d 49m 10.3s) | C | 60 | 18.9 | 8362 | 2025-12-14 11:36:24 | MASTER-Tunka | (22h 53m 50.59s , +31d 47m 07.2s) | C | 60 | 19.1 | 8362 | 2025-12-14 11:36:24 | MASTER-Tunka | (22h 53m 09.70s , +31d 54m 28.8s) | C | 60 | 18.7 | 8437 | 2025-12-14 11:37:39 | MASTER-Tunka | (23h 11m 37.14s , +31d 48m 53.9s) | C | 60 | 19.1 | 8437 | 2025-12-14 11:37:39 | MASTER-Tunka | (23h 10m 56.14s , +31d 56m 17.6s) | C | 60 | 18.6 | 8512 | 2025-12-14 11:38:54 | MASTER-Tunka | (22h 46m 46.23s , +33d 40m 52.2s) | C | 60 | 19.3 | 8512 | 2025-12-14 11:38:54 | MASTER-Tunka | (22h 46m 03.98s , +33d 48m 19.6s) | C | 60 | 18.8 | 8671 | 2025-12-14 11:41:33 | MASTER-Tunka | (22h 51m 47.69s , +39d 31m 45.6s) | C | 60 | 19.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43094. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41174] GRB 251214B: SVOM/C-GFT optical observations
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43093 SUBJECT: GRB 251214B: SVOM/C-GFT optical observations DATE: 25/12/14 11:59:55 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Zhe Kang (CHO), Chao WU (NAOC), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), report on behalf of the SVOM/C-GFT team: We observed the field of GRB 251214B detected by Fermi/GBM (Fermi GBM team, GCN 43088) and Swift/BAT (Eyles-Ferris et al., GCN 43089) with LATIOS on SVOM/C-GFT. Observations started at 2025-12-14T09:12:24 UTC, ~10.12 min after the trigger. The optical counterpart (Eyles-Ferris et al., GCN 43089) was clearly detected in our stacked images of band g, r , and i. The magnitudes are: |[date-obs(mid-time)] | Mid_t-T0(min) | exposure time (s) | band | mag (AB) | mag_err| |--------------------|--------------|-------------------|------|----------|--------| |2025-12-14T09:12:42 | 10.75 | 3x10 | i | 16.56 |0.070| |2025-12-14T09:26:55 | 24.64 | 5x30 | g | 18.56 |0.090| |2025-12-14T09:40:03 | 37.77 | 6x30 | r | 18.33 |0.050| The photometry was calibrated against UCAC4 catalogue and no correction for Galactic dust extinction was applied. We thank the observation assistants Chun-Lei Guo and Yin-Huai Hao at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43093. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41173] EP251214a: COLIBRÍ optical upper limit
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43092 SUBJECT: EP251214a: COLIBRÍ optical upper limit DATE: 25/12/14 11:44:06 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Stéphane Basa (UAR Pytheas), Leonardo García García (UNAM), Noémie Globus (UNAM), Benjamin Schneider (LAM), Jean-Grégoire Ducoin (CPPM), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Enrique Moreno Méndez (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM). We imaged the field of EP251214a (Y.-H. I. Yin et al., GCN Circ. 43087) potentially associated with GRB 251214A reported by the Fermi GBM Team (GCN Circ. 43085), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-14 at 09:12:10.65 to 09:56:13.15 UTC (from 6.75 to 7.49 hr after the trigger) and obtained 32 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analyzed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the WXT uncertainty region (Y.-H. I. Yin et al., GCN Circ. 43087) down to the following 5-sigma limit: r > 23.1 z > 21.6 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43092. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41172] Swift GRB 251214B: Global MASTER-Net observations report
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43091 SUBJECT: Swift GRB 251214B: Global MASTER-Net observations report DATE: 25/12/14 10:37:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 251214B ( R. A. J. Eyles-Ferris et al., GCN 43089) errorbox 4148 sec after notice time and 4708 sec after trigger time at 2025-12-14 10:20:46 UT, with upper limit up to 17.4 mag. Observations started at twilight. The observations began at zenith distance = 61 deg. The sun altitude is -11.8 deg. The galactic latitude b = -46 deg., longitude l = 50 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070785 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 4739 | MASTER-Tunka | C | 60 | 16.3 | 4799 | MASTER-Tunka | C | 180 | 17.4 | Coadd 4739 | MASTER-Tunka | C | 60 | 15.9 | 4814 | MASTER-Tunka | C | 60 | 16.8 | 4814 | MASTER-Tunka | C | 60 | 16.4 | 4886 | MASTER-Tunka | C | 60 | 16.7 | 4886 | MASTER-Tunka | C | 60 | 17.0 | 4963 | MASTER-Tunka | C | 60 | 17.1 | 4963 | MASTER-Tunka | C | 60 | 16.8 | 5036 | MASTER-Tunka | C | 60 | 16.8 | 5036 | MASTER-Tunka | C | 60 | 16.5 | 5111 | MASTER-Tunka | C | 60 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43091. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41171] EP251214.305: COLIBRÍ optical upper limit
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43090 SUBJECT: EP251214.305: COLIBRÍ optical upper limit DATE: 25/12/14 09:59:58 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Stéphane Basa (UAR Pytheas), Leonardo García García (UNAM), Benjamin Schneider (LAM), Jean-Grégoire Ducoin (CPPM), Noémie Globus (UNAM), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Enrique Moreno Méndez (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM). We imaged the field of the alert EP251214.305 using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-14T08:18:20.806 to 2025-12-14T09:02:02.207 UTC (from 3478 to 6099 seconds after the trigger) and obtained 1920 seconds of simultaneous exposure in the r and z filters. The data were reduced, coadded and analyzed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the WXT uncertainty region down to the following 5-sigma limit: r > 22.69 z > 21.83 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43090. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41170] GRB 251214B: Swift detection of a burst with an optical counterpart
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43089 SUBJECT: GRB 251214B: Swift detection of a burst with an optical counterpart DATE: 25/12/14 09:28:08 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. A. J. Eyles-Ferris (U Leicester), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester), D. M. Palmer (LANL) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team: At 09:02:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251214B (trigger=1423875). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 330.217, -9.167 which is RA(J2000) = 22h 00m 52s Dec(J2000) = -09d 10' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 10 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 09:03:18.2 UT, 60.7 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 330.21095, -9.16335 which is equivalent to: RA(J2000) = 22h 00m 50.63s Dec(J2000) = -09d 09' 48.1" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 25 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.01 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.2 (+2.80/-2.44) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 63 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at RA(J2000) = 22:00:50.52 = 330.21052 DEC(J2000) = -09:09:46.7 = -9.16296 with a 90%-confidence error radius of about 1.10 arc sec. This position is 3.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.47. No correction has been made for the expected extinction corresponding to E(B-V) of 0.039. Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43089. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41169] GRB 251214B: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43088 SUBJECT: GRB 251214B: Fermi GBM Final Real-time Localization DATE: 25/12/14 09:13:00 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 09:02:18 UT on 14 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214B (trigger 787395743.028482 / 251214377). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 329.6, Dec = -18.5 (J2000 degrees, equivalent to J2000 21h 58m, -18d 30'), with a statistical uncertainty of 9.3 degrees. The angle from the Fermi LAT boresight is 91.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214377/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43088. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41168] EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43087 SUBJECT: EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A DATE: 25/12/14 08:15:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), Y. H. Jiang (NJU), Y. Q. Zhao (PRIC, USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214a. The source, with a signal-to-noise ratio of 6, did not trigger the WXT on-board trigger unit. The observation started at 2025-12-14T02:27:01 (UTC) and lasted for 3043 seconds. The WXT position of the source is R.A. = 148.471 deg, DEC = 21.053 deg (J2000) with an uncertainty of 3.1 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.82 x 10^20 cm^-2 and a photon index of 1.84 (-/+0.94). The derived average unabsorbed 0.5-4 keV flux is 1.05 (-0.42/+0.70) x 10^-11 erg/s/cm^2. The position of EP251214a is around 4.86 deg away from GRB 251214A reported by the Fermi GBM Team (GCN 43085), and the observation was carried out around 2 hours after the GRB trigger. Given the temporal proximity and spatial consistency, we thus consider the EP-WXT detection the possible X-ray afterglow of GRB 251214A. EP-FXT follow-up observation has been arranged. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43087. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41167] Fermi GRB 251214A: Global MASTER-Net observations report
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43086 SUBJECT: Fermi GRB 251214A: Global MASTER-Net observations report DATE: 25/12/14 00:45:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251214A ( Fermi GBM team, GCN 43085) errorbox 201 sec after notice time and 238 sec after trigger time at 2025-12-14 00:15:13 UT, with upper limit up to 14.7 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -7.0 deg. The galactic latitude b = 52 deg., longitude l = 219 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070442 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 239 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 12m 20.99s , +17d 57m 22.4s) | C | 1 | 14.4 | 240 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.4s) | C | 3 | 14.7 | Coadd 239 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 11m 48.16s , +18d 04m 24.3s) | C | 1 | 14.2 | 245 | 2025-12-14 00:15:18 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.3s) | C | 1 | 14.3 | 245 | 2025-12-14 00:15:18 | MASTER-Tunka | (10h 11m 48.16s , +18d 04m 24.2s) | C | 1 | 14.1 | 250 | 2025-12-14 00:15:24 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.0s) | C | 1 | 14.0 | 250 | 2025-12-14 00:15:24 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 24.0s) | C | 1 | 14.0 | 256 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 23.6s) | C | 1 | 13.8 | 256 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 21.9s) | C | 1 | 14.0 | 257 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.0s) | C | 3 | 14.4 | Coadd 262 | 2025-12-14 00:15:36 | MASTER-Tunka | (10h 12m 21.01s , +17d 57m 21.7s) | C | 1 | 13.9 | 262 | 2025-12-14 00:15:36 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 23.7s) | C | 1 | 13.8 | 267 | 2025-12-14 00:15:41 | MASTER-Tunka | (10h 11m 48.18s , +18d 04m 23.4s) | C | 1 | 13.8 | 267 | 2025-12-14 00:15:41 | MASTER-Tunka | (10h 12m 21.02s , +17d 57m 21.5s) | C | 1 | 13.9 | 273 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.5s) | C | 1 | 13.9 | 274 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.5s) | C | 3 | 14.4 | Coadd 273 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 11m 48.20s , +18d 04m 23.3s) | C | 1 | 13.5 | 278 | 2025-12-14 00:15:52 | MASTER-Tunka | (10h 12m 21.04s , +17d 57m 21.1s) | C | 1 | 14.0 | 279 | 2025-12-14 00:15:52 | MASTER-Tunka | (10h 11m 48.20s , +18d 04m 22.9s) | C | 1 | 13.7 | 285 | 2025-12-14 00:15:58 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.1s) | C | 1 | 13.9 | 285 | 2025-12-14 00:15:58 | MASTER-Tunka | (10h 11m 48.23s , +18d 04m 22.8s) | C | 1 | 13.8 | 290 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 12m 21.06s , +17d 57m 20.6s) | C | 1 | 13.8 | 291 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 12m 21.06s , +17d 57m 20.6s) | C | 3 | 14.3 | Coadd 291 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 11m 48.25s , +18d 04m 22.6s) | C | 1 | 13.8 | 296 | 2025-12-14 00:16:09 | MASTER-Tunka | (10h 12m 21.03s , +17d 57m 20.4s) | C | 1 | 13.8 | 296 | 2025-12-14 00:16:09 | MASTER-Tunka | (10h 11m 48.23s , +18d 04m 22.2s) | C | 1 | 13.5 | 302 | 2025-12-14 00:16:15 | MASTER-Tunka | (10h 12m 21.04s , +17d 57m 20.4s) | C | 1 | 13.8 | 302 | 2025-12-14 00:16:15 | MASTER-Tunka | (10h 11m 48.25s , +18d 04m 22.3s) | C | 1 | 13.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43086. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41166] Fermi GRB 251214A: Global MASTER-Net observations report
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43086 SUBJECT: Fermi GRB 251214A: Global MASTER-Net observations report DATE: 25/12/14 00:45:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251214A ( Fermi GBM team, GCN 43085) errorbox 201 sec after notice time and 238 sec after trigger time at 2025-12-14 00:15:13 UT, with upper limit up to 14.7 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -7.0 deg. The galactic latitude b = 52 deg., longitude l = 219 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3070442 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 239 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 12m 20.99s , +17d 57m 22.4s) | C | 1 | 14.4 | 240 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.4s) | C | 3 | 14.7 | Coadd 239 | 2025-12-14 00:15:13 | MASTER-Tunka | (10h 11m 48.16s , +18d 04m 24.3s) | C | 1 | 14.2 | 245 | 2025-12-14 00:15:18 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.3s) | C | 1 | 14.3 | 245 | 2025-12-14 00:15:18 | MASTER-Tunka | (10h 11m 48.16s , +18d 04m 24.2s) | C | 1 | 14.1 | 250 | 2025-12-14 00:15:24 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.0s) | C | 1 | 14.0 | 250 | 2025-12-14 00:15:24 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 24.0s) | C | 1 | 14.0 | 256 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 23.6s) | C | 1 | 13.8 | 256 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 21.9s) | C | 1 | 14.0 | 257 | 2025-12-14 00:15:30 | MASTER-Tunka | (10h 12m 21.00s , +17d 57m 22.0s) | C | 3 | 14.4 | Coadd 262 | 2025-12-14 00:15:36 | MASTER-Tunka | (10h 12m 21.01s , +17d 57m 21.7s) | C | 1 | 13.9 | 262 | 2025-12-14 00:15:36 | MASTER-Tunka | (10h 11m 48.17s , +18d 04m 23.7s) | C | 1 | 13.8 | 267 | 2025-12-14 00:15:41 | MASTER-Tunka | (10h 11m 48.18s , +18d 04m 23.4s) | C | 1 | 13.8 | 267 | 2025-12-14 00:15:41 | MASTER-Tunka | (10h 12m 21.02s , +17d 57m 21.5s) | C | 1 | 13.9 | 273 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.5s) | C | 1 | 13.9 | 274 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.5s) | C | 3 | 14.4 | Coadd 273 | 2025-12-14 00:15:47 | MASTER-Tunka | (10h 11m 48.20s , +18d 04m 23.3s) | C | 1 | 13.5 | 278 | 2025-12-14 00:15:52 | MASTER-Tunka | (10h 12m 21.04s , +17d 57m 21.1s) | C | 1 | 14.0 | 279 | 2025-12-14 00:15:52 | MASTER-Tunka | (10h 11m 48.20s , +18d 04m 22.9s) | C | 1 | 13.7 | 285 | 2025-12-14 00:15:58 | MASTER-Tunka | (10h 12m 21.05s , +17d 57m 21.1s) | C | 1 | 13.9 | 285 | 2025-12-14 00:15:58 | MASTER-Tunka | (10h 11m 48.23s , +18d 04m 22.8s) | C | 1 | 13.8 | 290 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 12m 21.06s , +17d 57m 20.6s) | C | 1 | 13.8 | 291 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 12m 21.06s , +17d 57m 20.6s) | C | 3 | 14.3 | Coadd 291 | 2025-12-14 00:16:04 | MASTER-Tunka | (10h 11m 48.25s , +18d 04m 22.6s) | C | 1 | 13.8 | 296 | 2025-12-14 00:16:09 | MASTER-Tunka | (10h 12m 21.03s , +17d 57m 20.4s) | C | 1 | 13.8 | 296 | 2025-12-14 00:16:09 | MASTER-Tunka | (10h 11m 48.23s , +18d 04m 22.2s) | C | 1 | 13.5 | 302 | 2025-12-14 00:16:15 | MASTER-Tunka | (10h 12m 21.04s , +17d 57m 20.4s) | C | 1 | 13.8 | 302 | 2025-12-14 00:16:15 | MASTER-Tunka | (10h 11m 48.25s , +18d 04m 22.3s) | C | 1 | 13.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43086. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41165] GRB 251214A: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Dec '25

14 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43085 SUBJECT: GRB 251214A: Fermi GBM Final Real-time Localization DATE: 25/12/14 00:21:49 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 00:11:15 UT on 14 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214A (trigger 787363880.165798 / 251214008). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 152.4, Dec = 17.9 (J2000 degrees, equivalent to J2000 10h 09m, 17d 53'), with a statistical uncertainty of 4.9 degrees. The angle from the Fermi LAT boresight is 61.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214008/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214008/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251214008/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43085. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41164] EP251212a: Global MASTER-Net observations report
by GCN Circulars 13 Dec '25

13 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43084 SUBJECT: EP251212a: Global MASTER-Net observations report DATE: 25/12/13 20:09:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP251212a ( EP Team et al., GCN 43081) errorbox 7432 sec after notice time and 60333 sec after trigger time at 2025-12-13 06:29:42 UT, with upper limit up to 20.8 mag. The observations began at zenith distance = 21 deg. The sun altitude is -28.6 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP251212a errorbox 56042 sec after notice time and 1 days 22543 sec after trigger time at 2025-12-13 19:59:52 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 74 deg. The sun altitude is -45.8 deg. The galactic latitude b = 14 deg., longitude l = 249 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3069779 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 60363 | 2025-12-13 06:29:42 | MASTER-OAFA | (08h 52m 06.66s , -23d 02m 09.3s) | C | 60 | 20.0 | 60544 | 2025-12-13 06:32:43 | MASTER-OAFA | (08h 52m 13.47s , -23d 02m 07.8s) | C | 60 | 20.0 | 60724 | 2025-12-13 06:35:42 | MASTER-OAFA | (08h 52m 12.36s , -23d 02m 47.2s) | C | 60 | 19.8 | 60799 | 2025-12-13 06:36:58 | MASTER-OAFA | (09h 00m 51.90s , -23d 01m 25.6s) | C | 60 | 20.0 | 60949 | 2025-12-13 06:36:58 | MASTER-OAFA | (09h 00m 51.89s , -23d 01m 25.7s) | C | 360 | 20.8 | Coadd 60878 | 2025-12-13 06:38:16 | MASTER-OAFA | (09h 00m 52.01s , -23d 02m 51.7s) | C | 60 | 20.0 | 60952 | 2025-12-13 06:39:31 | MASTER-OAFA | (09h 00m 55.66s , -23d 01m 23.0s) | C | 60 | 20.0 | 62872 | 2025-12-13 07:11:31 | MASTER-OAFA | (09h 00m 51.73s , -23d 02m 08.7s) | C | 60 | 20.0 | 62949 | 2025-12-13 07:12:47 | MASTER-OAFA | (09h 00m 56.52s , -23d 01m 41.3s) | C | 60 | 20.0 | 63023 | 2025-12-13 07:14:02 | MASTER-OAFA | (09h 00m 54.42s , -23d 00m 05.6s) | C | 60 | 20.1 | 108959 | 2025-12-13 19:59:52 | MASTER-Tunka | (08h 56m 23.31s , -22d 50m 56.5s) | C | 30 | 15.9 | 109002 | 2025-12-13 20:00:36 | MASTER-Tunka | (08h 56m 22.49s , -22d 49m 57.8s) | C | 30 | 15.9 | 109050 | 2025-12-13 20:01:24 | MASTER-Tunka | (08h 56m 28.21s , -22d 50m 58.5s) | C | 30 | 16.2 | 109094 | 2025-12-13 20:02:07 | MASTER-Tunka | (08h 56m 21.99s , -22d 52m 00.7s) | C | 30 | 16.6 | 109094 | 2025-12-13 20:02:07 | MASTER-Tunka | (08h 56m 04.58s , -22d 45m 54.5s) | C | 30 | 14.9 | 109145 | 2025-12-13 20:02:58 | MASTER-Tunka | (08h 56m 27.67s , -22d 51m 54.9s) | C | 30 | 16.9 | 109145 | 2025-12-13 20:02:58 | MASTER-Tunka | (08h 56m 11.31s , -22d 45m 17.0s) | C | 30 | 12.4 | 109186 | 2025-12-13 20:03:40 | MASTER-Tunka | (08h 56m 25.45s , -22d 50m 22.2s) | C | 30 | 17.3 | 109186 | 2025-12-13 20:03:40 | MASTER-Tunka | (08h 56m 06.73s , -22d 43m 38.7s) | C | 30 | 13.0 | 109230 | 2025-12-13 20:04:23 | MASTER-Tunka | (08h 56m 25.51s , -22d 52m 02.9s) | C | 30 | 17.4 | 109230 | 2025-12-13 20:04:23 | MASTER-Tunka | (08h 56m 06.86s , -22d 45m 19.2s) | C | 30 | 12.9 | 109273 | 2025-12-13 20:05:06 | MASTER-Tunka | (08h 56m 13.03s , -22d 43m 50.4s) | C | 30 | 12.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43084. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41163] EP251212a: KAIT optical upper limit
by GCN Circulars 13 Dec '25

13 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43083 SUBJECT: EP251212a: KAIT optical upper limit DATE: 25/12/13 09:04:48 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP251212a (Yang et al., GCN 43076; Salunke et al., GCN 43082) starting at 11:09, Dec 12 UT, about 4.95 hours after the burst. A set of 38x60s clear (roughly R) filter images were obtained. In our coadd image, we did not detect any new source within the EP-FXT error circle (Yang et al., GCN 43081) down to a limiting mag of 21.2 mag (Vega) at a mid-time of 5.57 hours after the burst. Our result is consistent with the upper limit reported from COLIBRÍ observations (Ducoin et al., GCN 43077). View this GCN Circular online at https://gcn.nasa.gov/circulars/43083. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41162] EP251212a / GRB 251212A: AstroSat CZTI detection
by GCN Circulars 13 Dec '25

13 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43082 SUBJECT: EP251212a / GRB 251212A: AstroSat CZTI detection DATE: 25/12/13 07:55:15 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251212A which was also detected by Konus-Wind (via IPN Notices), about 20 s after the trigger time of EP251212a detected by Einstein Probe / WXT (Yang et. al., GCN Circ. 43076). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-12 06:13:13.50 UTC. The measured peak count rate associated with the burst is 64 (+20, -21) counts/s above the background in the data of one quadrant (out of four), with a total of 136 (+55, -58) counts. The local mean background count rate was 83 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 5.6 (+0.6, -3.8) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-12 06:13:13.22 UTC. The measured peak count rate associated with the burst is 475 (+72, -74) counts/s above the background in the combined data of all quadrants, with a total of 1524 (+245, -269) counts. The local mean background count rate was 1568 (+7, -9) counts/s. We measure a T90 of 5.7 (+0.9, -1.9) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43082. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41161] EP251212a: EP-FXT follow-up observation
by GCN Circulars 13 Dec '25

13 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43081 SUBJECT: EP251212a: EP-FXT follow-up observation DATE: 25/12/13 04:25:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. Yang (ZZU), Y. H. Jiang (NJU), Z. X. Li, G. L. Huang, J. Y. Cao (IHEP), S. Y. Fu (HUST), Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP251212a (GCN 43076) at 2025-12-12T13:44:09 (UTC), about 7.5 hours after the WXT detection, with an exposure time of 2.7 ks. FXT detected an uncatalogued source within the WXT error circle at R.A. = 134.0471, DEC = -23.2992 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT X-ray spectrum of this uncatalogued source can be fitted with an absorbed powerlaw with a hydrogen column density of 1.1 x 10^21 cm^-2 and a photon index of 1.7. The derived unabsorbed 0.5-10 keV flux is approximately 1.54 x 10^-12 erg/s/cm^2. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43081. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41160] GRB 251211B: AstroSat CZTI detection
by GCN Circulars 13 Dec '25

13 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43080 SUBJECT: GRB 251211B: AstroSat CZTI detection DATE: 25/12/13 04:13:33 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), U. Pathak (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251211B, which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 43072). The source was faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-12-11 20:32:04.31 UTC. The measured peak count rate associated with the burst is 176 (+60, -53) counts/s above the background in the combined data of all quadrants, with a total of 367 (+222, -238) counts. The local mean background count rate was 1180 (+8, -8) counts/s. Due to the intrinsic 1 s binning of veto data and the relatively faint detection, we cannot reliably estimate a T90 for this burst. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43080. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41159] IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43079 SUBJECT: IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility DATE: 25/12/12 18:25:09 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Robert Stein (JSI), Jannis Necker (Leiden University), Akshay Eranhalodi (DESY) and Anna Franckowiak (Ruhr University Bochum) report On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-251210A (Zegarelli et. al, GCN 43064) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2025-12-11 02:31 UTC, approximately 15.4 hours after event time. We covered 97.7% (1.6 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with the following candidate: +--------------------------------------------------------------------------------+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | +--------------------------------------------------------------------------------+ | ZTF25acgniiw | ------- | 035.5190217 | +20.3633434 | r | 20.55 | 0.09 | +--------------------------------------------------------------------------------+ ZTF25acgniiw was first detected on 2025-11-24. Its position is coincident with a quasar listed in MILLIQUAS (Flesch et al., 2023). Because there is no sign of contemporaneous flaring activity, ZTF25acgniiw is likely not associated with IceCube-251210A. This is in agreement with previous reports (Becerra et al. 2025, GCN 43071). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/43079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41158] GRB 251209A: NuSTAR detection of prompt emission
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43078 SUBJECT: GRB 251209A: NuSTAR detection of prompt emission DATE: 25/12/12 18:15:43 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 251209A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2025-12-09 13:24:26 (with a resolution ~5-seconds). This is consistent with the detections of GRB 251209A by Fermi/GBM (Fermi GBM Team, GCN Circ. 43048) and AstroSat/CZTI (Tembhurnikar et al., GCN Circ. 43066). The NusTAR trigger is consistent with triggering on the longer-duration “main burst” as seen in the Fermi-GBM lightcurves. The NuSTAR CsI shield data are recorded at 1 Hz. We detect two peaks lasting for ~30-s, consistent with the detections of Fermi/GBM & AstroSat/CZTI. A fainter, narrower initial burst at 2025-12-09 13:24:03 is also seen by eye in the NuSTAR lightcurves but did not trigger the automated algorithm. The peak count rate is ~3000-cps over a baseline rate of ~1,000-cps during this time period. The Fermi/GBM localization (GCN Circ. 43048) at RA = 214.2, Dec = 43.1 implies an offset from the NuSTAR boresight of 92-deg (i.e. from the side of the instrument) and an offset from the geocenter of 120-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/251209A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/43078. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41157] EP251212a : COLIBRÍ optical upper limit
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43077 SUBJECT: EP251212a : COLIBRÍ optical upper limit DATE: 25/12/12 14:49:35 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Enrique Moreno Méndez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the EP251212a (Yang et al., GCN Circ. 43076) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-12T11:08:54.118 to 11:27:56.049 UTC (from 4.94 to 5.25 hours after the trigger) and obtained 960 seconds of simultaneous exposure in the r and z filters. The data were reduced, coadded and analyzed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the WXT uncertainty region (Yang et al., GCN Circ. 43076) down to the following 5-sigma limit: r > 22.59 z > 21.41 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43077. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41156] EP251212a: Einstein Probe detection of an X-ray transient
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43076 SUBJECT: EP251212a: Einstein Probe detection of an X-ray transient DATE: 25/12/12 12:39:39 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. Yang (ZZU), Y. H. Jiang (NJU), Z. X. Li, G. L. Huang, J. Y. Cao (IHEP), S. Y. Fu (HUST), Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251212a. The source did not trigger the WXT on-board trigger unit. A GCN Notice was sent manually (trigger ID: 11916652735). The ground analysis of the WXT data shows that the event started at T0=2025-12-12T06:12:52 (UTC) and lasted for around 100 seconds. The WXT position of the source is R.A. = 134.041 deg, DEC = -23.279 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a hydrogen column density of 3.6 x 10^21 cm^-2 and a photon index of 1.1. The derived average unabsorbed 0.5-4 keV flux is 2.0 x 10^-9 erg/s/cm^2. The follow-up observation with the Follow-up X-ray Telescope (FXT) has been scheduled. Further information will be updated when the FXT telemetry data are received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/43076. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41155] Fermi-LAT Gamma-ray Observations of IceCube-251210A
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43075 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251210A DATE: 25/12/12 09:04:29 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC251210A neutrino event (GCN 43064) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-12-10 at 11:06:14.40 UTC (T0) with J2000 position RA = 35.29 (+0.68, -0.69) deg, Decl. = 20.34 (+0.64, -0.71) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC251210A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC251210A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251210A best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.2e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <1.5e-08 (<9.1e-08) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43075. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41154] IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43074 SUBJECT: IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/12/12 05:49:23 GMT FROM: Sam Hori at IceCube/U Wisc-Madison <sahori(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-251210A (https://gcn.nasa.gov/circulars/43064) in a time range of 1000 seconds centered on the alert event time (2025-12-10 10:57:54.429 UTC to 2025-12-10 11:14:34.429 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-251210A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251210A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 9e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-12-09 11:06:14.429 UTC to 2025-12-11 11:06:14.429 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.7e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251210A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/43074. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41153] Fermi GRB 251211B: Global MASTER-Net observations report
by GCN Circulars 12 Dec '25

12 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43073 SUBJECT: Fermi GRB 251211B: Global MASTER-Net observations report DATE: 25/12/12 00:15:55 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251211B ( Fermi GBM team, GCN 43072) errorbox 622 sec after notice time and 629 sec after trigger time at 2025-12-11 20:42:33 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 72 deg. The sun altitude is -39.1 deg. The galactic latitude b = 48 deg., longitude l = 279 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3068576 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 643 | 2025-12-11 20:42:33 | MASTER-Tunka | (11h 44m 16.21s , -11d 00m 25.5s) | C | 25 | 16.9 | 665 | 2025-12-11 20:42:33 | MASTER-Tunka | (11h 44m 16.21s , -11d 00m 25.6s) | C | 70 | 17.5 | Coadd 671 | 2025-12-11 20:43:02 | MASTER-Tunka | (11h 44m 16.37s , -11d 00m 25.6s) | C | 25 | 16.9 | 697 | 2025-12-11 20:43:30 | MASTER-Tunka | (11h 44m 16.51s , -11d 00m 25.3s) | C | 20 | 16.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43073. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0