December 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41254] EP 251220a: GOTO optical counterpart detection
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43169 SUBJECT: EP 251220a: GOTO optical counterpart detection DATE: 25/12/21 11:08:01 GMT FROM: Amit Kumar at The Open University, UK <amitkundu515(a)gmail.com> A. Kumar, G. Ramsay, M. Kennedy, D. O'Neill, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) that serendipitously covered the field of EP 251220a (Liu et al. GCN 43162). The observations were conducted with GOTO-North at 2025-12-20 19:51:42 UT (11.4 hours post-trigger), consisting of 4x45s exposures in the GOTO L-band (400-700 nm). Difference imaging was performed using deeper template observations of the same pointings. We detect the optical counterpart of EP 251220a (Álvarez et al., GCN 43167) in the GOTO L-band at 3σ, with a magnitude of 20.7 ± 0.3 (AB). Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/43169. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41253] GRB 251221A: COLIBRÍ detection of the optical counterpart
by GCN Circulars 21 Dec '25

21 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43168 SUBJECT: GRB 251221A: COLIBRÍ detection of the optical counterpart DATE: 25/12/21 06:43:18 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), 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 Fermi/Swift GRB 251221A (Fermi GBM team, GCN Circ. 43164; Ambrosi et al., GCN Circ. 43166) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-21 05:25:46 to 06:08 UTC (from 75 seconds to 43 minutes after the trigger) and obtained 1690 seconds of simultaneous exposure in the r and z filters. The data were reduced and coadded 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. We detected an uncatalogued, fading source at RA (J2000) = 06:45:42.73 = 101.42804 deg Dec (J2000) = +00:43:54.8 = 0.73189 deg with an uncertainty of 0.5 arcsec and preliminary magnitudes of: r > 24.2 (3-sigma) z = 22.26 +/- 0.18 The XRT uncertainty region (Ambrosi et al., GCN Circ. 43166) has a 90% confidence radius of 1.8 arcsec, and this source is 2.3 arcsec from the center. We suggest therefore that this is the optical counterpart of the GRB. The lack of detection in r is consistent with the high Galactic extinction in this direction of A_V = 3.1 mag (Schlafly et al. 2011). 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/43168. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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