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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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[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…

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