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[vsnet-grb-info 40953] EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42884 SUBJECT: EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient DATE: 25/11/29 05:21:00 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wu, Y. H. Jiang, C. Y. Dai (NJU), Y. Wang (PMO), H. C. Ding, T. Wu (AHNU), W. J. Zhang, Y. Liu (NAO, CAS), 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 EP251129a. The transient triggered EP-WXT (ID: 01709248891) at 2025-11-29T03:14:23 (UTC). The WXT position of the source is R.A. = 224.294 deg, DEC = 79.301 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 224.3331 deg, DEC = 79.2903 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). The position of FXT is 36 arcsec from SVOM/MXT detection of GRB 251129A (Tan et al., GCN 42877), and 10 arcsec from its optical counterpart (Angulo et al., GCN 42883). Further information will be updated when the telemetry data is 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/42884. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40952] GRB 251129A: Correction to the position of the optical counterpar
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42883 SUBJECT: GRB 251129A: Correction to the position of the optical counterpar DATE: 25/11/29 04:48:59 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan Watson (UNAM) reports: The position of the optical counterpart given by Angulo et al. (GCN 42880) was not given completely correctly. The position was given correctly in sexagesimal but not in degrees. The correct position is: RA(J2000) = 14:57:18.88 = 224.3286 degrees Dec(J2000) = +79:17:34.8 = 79.2930 degrees We apologize for this error. We thank Huali Li for bringing this mistake to our attention. View this GCN Circular online at https://gcn.nasa.gov/circulars/42883. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40951] GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42882 SUBJECT: GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data DATE: 25/11/29 04:12:26 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> C. Wu, H. L. Li, L.P. Xin, Y. L. Qiu (NAOC), J. T. Palmerio (CEA), W. J. Tan (IHEP), D. F. Kong (GXU) report on behalf of the SVOM team. After the trigger by SVOM/ECLAIRs at 2025-11-29T02:32:05 UTC (T0), SVOM/VT performed an automatic slew to the burst GRB 251129A (sb25112901, Tan et al., GCN 42879). The observation began at 2025-11-29T02:43:03, 658 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart reported (Angulo et al., GCN 42880) was clearly detected in the 1-bit subimages and source lists downloaded via VHF network in both channels. The magnitudes are : Mid_time Band Magnitude (AB) 808 sec VT_B 18.63+/-0.01 mag 808 sec VT_R 18.02+/-0.01 mag Our photometry was derived in AB magnitude and not corrected for Galactic extinction. Given the VT color, it is likely a low redshift GRB. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42882. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40950] GRB 251128A: Fermi GBM Observation
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42881 SUBJECT: GRB 251128A: Fermi GBM Observation DATE: 25/11/29 03:48:05 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA), M. Godwin (UAH), Padraig McDermott (UCD), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 04:22:21.61 UT on 28 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251128A (trigger 785996546/251128182; GCN 42865), which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 42874). The angle from the Fermi LAT boresight is 114 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 47 s (50-300 keV). The time-averaged spectrum from T0-0.0 to T0+44 s is best fit by a Band function with Epeak = 124 +/- 2, alpha = -0.92 +/- 0.01, and beta = -2.0 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (1.95 +/- 0.13)e-05 ergs/cm^2. The 1-sec peak photon flux measured starting from T0+9.1 s in the 10-1000 keV band is 11.8 +/- 0.5 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/42881. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40949] GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42880 SUBJECT: GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 25/11/29 03:38:10 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Nikos Mandarakas (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), 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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Wenjun Tan (IHEP), Defeng Kong (GXU), Wenjin Xie (NAOC), Donghua Zhao (NAOC), Hatsune Goto (Kanazawa Univ.) report: We imaged the field of the SVOM GRB 251129A (Tan et al., GCN Circ. 42877) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-11-29 02:51:22 to 02:57:11 UTC (from 20.0 to 25.8 minutes after the trigger) and obtained 5 minutes of simultaneous exposure in the r and z filters. 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. We detect an uncatalogued source just outside the MXT error circle at: RA(J2000) = 14:57:18.88 = 224.2949 degrees Dec(J2000) = +79:17:34.8= 79.3050 degrees with an uncertainty of 0.5 arcsec. The preliminary magnitude derived for that source is: r = 18.30 +/- 0.01 z = 18.03 +/- 0.01 Further observations are ongoing. 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/42880. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40948] GRB 251129A: SVOM detection of a burst
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42879 SUBJECT: GRB 251129A: SVOM detection of a burst DATE: 25/11/29 03:15:27 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Wenjun Tan (IHEP), Defeng Kong (GXU), Wenjin Xie, Donghua Zhao (NAOC), Hatsune Goto (Kanazawa Univ.) report on behalf of the SVOM mission team: At 2025-11-29T02:32:05 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251129A (SVOM burst-id sb25112901). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.82 in the [8-50] keV energy band over a time window of 81.92 seconds starting at 2025-11-29T02:31:24. The localization of the best alert is R.A., Dec. 224.5380, 79.4287 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.96 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-11-29T02:45:53 UTC, 828 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 224.3258, 79.3004 degrees: R.A. (J2000) = 14h57m01.94s Dec. (J2000) = 79d18m32.94s with a 90% C.L. radius of 25.08 arcseconds. This location is 7.82 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Wenjun Tan: tanwj(a)ihep.ac.cn Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42879. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40947] SVOM GRB251129.11: Global MASTER-Net observations report
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42878 SUBJECT: SVOM GRB251129.11: Global MASTER-Net observations report DATE: 25/11/29 03:14:31 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 SVOM GRB251129.11 (trigger No 1764383485,14h 58m 09.12s , +79d 25m 43.3s, R=0.1493) errorbox 9 sec after notice time and 997 sec after trigger time at 2025-11-29 02:48:01 UT, with upper limit up to 18.9 mag. Observations started at twilight. The observations began at zenith distance = 45 deg. The sun altitude is -16.3 deg. The galactic latitude b = 36 deg., longitude l = 116 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3054567 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1057 | 2025-11-29 02:48:01 | MASTER-Kislovodsk | (14h 59m 33.58s , +79d 37m 30.3s) | C | 120 | 18.3 | 1177 | 2025-11-29 02:48:01 | MASTER-Kislovodsk | (14h 59m 33.58s , +79d 37m 30.3s) | C | 360 | 18.9 | Coadd 1057 | 2025-11-29 02:48:01 | MASTER-Kislovodsk | (15h 21m 37.07s , +79d 09m 16.3s) | C | 120 | 18.4 | 1197 | 2025-11-29 02:50:21 | MASTER-Kislovodsk | (14h 59m 33.13s , +79d 37m 36.2s) | C | 120 | 18.0 | 1197 | 2025-11-29 02:50:21 | MASTER-Kislovodsk | (15h 21m 37.81s , +79d 09m 22.5s) | C | 120 | 18.2 | 1337 | 2025-11-29 02:52:41 | MASTER-Kislovodsk | (14h 59m 32.62s , +79d 37m 42.8s) | C | 120 | 18.0 | 1337 | 2025-11-29 02:52:41 | MASTER-Kislovodsk | (15h 21m 38.00s , +79d 09m 30.4s) | C | 120 | 18.0 | 1487 | 2025-11-29 02:55:11 | MASTER-Kislovodsk | (14h 59m 32.17s , +79d 37m 50.0s) | C | 120 | 17.8 | 1607 | 2025-11-29 02:55:11 | MASTER-Kislovodsk | (14h 59m 32.18s , +79d 37m 50.0s) | C | 360 | 18.3 | Coadd 1487 | 2025-11-29 02:55:11 | MASTER-Kislovodsk | (15h 21m 37.94s , +79d 09m 39.5s) | C | 120 | 18.0 | 1627 | 2025-11-29 02:57:31 | MASTER-Kislovodsk | (14h 59m 31.42s , +79d 37m 57.4s) | C | 120 | 17.6 | 1627 | 2025-11-29 02:57:31 | MASTER-Kislovodsk | (15h 21m 37.84s , +79d 09m 49.2s) | C | 120 | 17.7 | 1766 | 2025-11-29 02:59:50 | MASTER-Kislovodsk | (14h 59m 30.65s , +79d 38m 04.2s) | C | 120 | 17.5 | 1766 | 2025-11-29 02:59:50 | MASTER-Kislovodsk | (15h 21m 37.58s , +79d 09m 57.9s) | C | 120 | 17.8 | 1906 | 2025-11-29 03:02:10 | MASTER-Kislovodsk | (14h 59m 29.69s , +79d 38m 11.3s) | C | 120 | 17.6 | 1906 | 2025-11-29 03:02:10 | MASTER-Kislovodsk | (15h 21m 37.28s , +79d 10m 06.9s) | C | 120 | 17.9 | 2046 | 2025-11-29 03:04:31 | MASTER-Kislovodsk | (14h 59m 28.84s , +79d 38m 19.5s) | C | 120 | 17.7 | 2046 | 2025-11-29 03:04:31 | MASTER-Kislovodsk | (15h 21m 37.01s , +79d 10m 17.3s) | C | 120 | 17.9 | 2186 | 2025-11-29 03:06:50 | MASTER-Kislovodsk | (14h 59m 27.87s , +79d 38m 27.5s) | C | 120 | 17.7 | 2186 | 2025-11-29 03:06:50 | MASTER-Kislovodsk | (15h 21m 36.63s , +79d 10m 27.4s) | C | 120 | 17.9 | 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/42878. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40946] GRB 251129A: SVOM detection of a burst
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42877 SUBJECT: GRB 251129A: SVOM detection of a burst DATE: 25/11/29 03:14:08 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Wenjun Tan (IHEP), Defeng Kong (GXU), Wenjin Xie, Donghua Zhao (NAOC), Hatsune Goto (Kanazawa univ.) report on behalf of the SVOM mission team: At 2025-11-29T02:32:05 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251129A (SVOM burst-id sb25112901). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.82 in the [8-50] keV energy band over a time window of 81.92 seconds starting at 2025-11-29T02:31:24. The localization of the best alert is R.A., Dec. 224.5380, 79.4287 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.96 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-11-29T02:45:53 UTC, 828 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 224.3258, 79.3004 degrees: R.A. (J2000) = 14h57m01.94s Dec. (J2000) = 79d18m32.94s with a 90% C.L. radius of 25.08 arcseconds. This location is 7.82 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Wenjun Tan: tanwj(a)ihep.ac.cn Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40945] GRB 251126A: Swift-BAT refined analysis
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42876 SUBJECT: GRB 251126A: Swift-BAT refined analysis DATE: 25/11/29 01:05:23 GMT FROM: Amy <yarleen(a)gmail.com> S. D. Barthelmy (GSFC), R. Caputo (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), 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 251126A (trigger #1417793) (Caputo et al., GCN Circ. 42843). The BAT ground-calculated position is RA, Dec = 99.939, 54.989 deg which is RA(J2000) = 06h 39m 45.4s Dec(J2000) = +54d 59' 21.9" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%. The mask-weighted light curve shows two overlapping pulses. The first pulse peaks at ~T+1 s, and the second pulse peaks at ~T+4 s. The overall structure starts at ~T0 and ends at ~T+10 s. T90 (15-350 keV) is 9.00 +- 2.00 sec (estimated error including systematics). The time-averaged spectrum from T-0.41 to T+10.59 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.43 +- 0.71, and Epeak of 51.4 +- 8.8 keV (chi squared 58.43 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.4 +- 0.4 x 10^-07 erg/cm2 and the 1-sec peak flux measured from T+0.59 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.76 +- 0.12 (chi squared 72.99 for 57 d.o.f.). 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/1417793 View this GCN Circular online at https://gcn.nasa.gov/circulars/42876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40944] GRB 251126A: TShAO, Mondy, and AbAO optical observations
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42875 SUBJECT: GRB 251126A: TShAO, Mondy, and AbAO optical observations DATE: 25/11/28 21:30:36 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> N. S. Pankov (HSE, IKI), A. A. Volnova (IKI), I. V. Reva (FAI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO), A. S. Moskvitin (SAO RAS), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851) with the Zeiss-1000 1m telescope of the Tien-Shan Observatory (TSHAO), the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy), and the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. The observations began at TSHAO on 2025-11-27 at 16:32 UT (~0.907 days after the trigger), further observations at AZT-33IK started at 18:55 (~1.01 days after the trigger), then followed by AbAO starting at 20:09 UT (~1.06 days after the trigger). The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al, GCN 42859; Volnova et al, GCN 42861; Breeveld, GCN 42863; Gupta et al., GCN 42864; Burkhonov et al., GCN 42866; Maksut et al., GCN 42868; Moskvitin et al., GCN 42870; Adami et al., GCN 42871) is not detected in the stacked frames from Zeiss-1000 and AS-32 and is seen in the stacked AZT-33IK frame. The preliminary results and observational details are provided below. Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-27 16:32:42 0.90745 35*90 R n/d n/d 21.2 TSHAO/Zeiss-1000 2025-11-27 18:55:21 1.01164 30*120 R 22.10 0.12 22.3 Mondy/AZT-33IK 2025-11-27 20:09:59 1.06624 72*60 R n/d n/d 21.9 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/42875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40943] GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42874 SUBJECT: GRB 251128A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/11/28 21:14:53 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251128A onboard (T0: 2025-11-28T04:22:21.61 UTC, Fermi Trig 785996546) 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 21.2 in a 4.096 s analysis time bin, starting at T0 - 1.024 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 550 deg2 and the 50% credible area is 74 deg2 The integrated probability inside the coded field of view is <1%. The NITRATES skymap is consistent with the Ferm/GBM localization reported in the final position notice (GCN 42865). The combined Fermi/GBM+NITRATES 90% credible area is 49 deg2 and the 50% credible area is 14 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=785996578/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/785996578/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/785996578/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=785996578 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/42874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40942] Fermi GRB 251128A: Global MASTER-Net observations report
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42873 SUBJECT: Fermi GRB 251128A: Global MASTER-Net observations report DATE: 25/11/28 15:15:24 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 251128A ( Fermi GBM team, GCN 42865) errorbox 36273 sec after notice time and 36305 sec after trigger time at 2025-11-28 14:27:27 UT, with upper limit up to 16.6 mag. Observations started at twilight. The observations began at zenith distance = 80 deg. The sun altitude is -9.0 deg. The galactic latitude b = 30 deg., longitude l = 166 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3053740 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 36336 | 2025-11-28 14:27:27 | MASTER-Kislovodsk | (07h 48m 24.78s , +54d 16m 19.6s) | C | 60 | 12.8 | 36336 | 2025-11-28 14:27:27 | MASTER-Kislovodsk | (07h 55m 11.13s , +53d 52m 14.4s) | C | 60 | 15.7 | 36496 | 2025-11-28 14:30:07 | MASTER-Kislovodsk | (07h 27m 49.20s , +52d 20m 52.7s) | C | 60 | 13.1 | 36496 | 2025-11-28 14:30:07 | MASTER-Kislovodsk | (07h 34m 27.48s , +51d 56m 56.6s) | C | 60 | 16.0 | 36575 | 2025-11-28 14:31:27 | MASTER-Kislovodsk | (07h 44m 12.06s , +56d 08m 56.4s) | C | 60 | 13.4 | 36575 | 2025-11-28 14:31:27 | MASTER-Kislovodsk | (07h 51m 27.99s , +55d 44m 39.4s) | C | 60 | 16.3 | 36655 | 2025-11-28 14:32:46 | MASTER-Kislovodsk | (07h 29m 20.17s , +53d 53m 04.8s) | C | 60 | 16.6 | 37136 | 2025-11-28 14:40:47 | MASTER-Kislovodsk | (07h 59m 24.43s , +51d 57m 45.1s) | C | 60 | 16.3 | 37136 | 2025-11-28 14:40:47 | MASTER-Kislovodsk | (07h 52m 49.54s , +52d 22m 11.6s) | C | 60 | 13.5 | 37608 | 2025-11-28 14:48:39 | MASTER-Kislovodsk | (07h 39m 46.04s , +50d 04m 30.2s) | C | 60 | 16.5 | 37608 | 2025-11-28 14:48:39 | MASTER-Kislovodsk | (07h 33m 24.33s , +50d 28m 49.0s) | C | 60 | 14.3 | 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/42873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40941] GRB 251127A: Glowbug gamma-ray detection
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42872 SUBJECT: GRB 251127A: Glowbug gamma-ray detection DATE: 25/11/28 14:57:16 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 251127A, which was also detected by Fermi/GBM (GCN 42852). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-27 03:17:42.528 with a duration of 14.8 s and a total significance of about 16.1 sigma. The light curve comprises a bright peak at ~T0 followed by a fainter multi-peaked structure. Note that data from ~T0+7s to +11s suffered from deadtime in various detectors. 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 telescopes 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/42872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40940] GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42871 SUBJECT: GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift DATE: 25/11/28 14:22:37 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), A. Saccardi (CEA/Irfu), B. Schneider (LAM), M. Dennefeld (IAP), E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRAL GRB collaboration: We carried out observations of the Swift GRB 251126A (Caputo et al., GCN 42843) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 3 exposures of 3 min in the r-band at a midtime of 2025-11-26 22:58 UT corresponding to T-T0 = 3.79 hours. The afterglow reported by Swain et al. (GCN 42844), Lipunov et al. (GCN 42847), Fu et al. (GCN 42848), Reguitti et al. (GCN 42849), Broens et al. (GCN Circ. 42850), Angulo et al. (GCN 42855), Pulido-Torres et al. (GCN 42856), Gupta et al. (GCN 42857), Cotter et al. (GCN 42858), Seki et al. (GCN 42859), Volnova et al. (GCN 42861), Breeveld and Caputo (GCN 42863), Gupta et al. (GCN 42864), Burkhonov et al. (GCN 42866), Maksut et al. (GCN 42868) and Moskvitin et al. (GCN 42870) is very well detected in r’ with a preliminary magnitude of : r’ = 20.1 +/- 0.13 We also obtained 1 exposure of 600s in the g-band at a midtime of 2025-11-27 00:38 UT. The afterglow is only barely visible with an upper magnitude limit of : g’ > 21.9 (S/N=3) The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction. In addition, a spectrum covering the wavelength range 4200-8000 AA was secured with the MISTRAL spectroscopic blue setting, starting at 23:10 UT (midtime = T0+4.5h) with a total exposure time of 2x1800 s. In a preliminary reduction of the spectrum, a faint trace is detected down to ~5600 AA (in the flux calibrated spectrum), where a spectral break is observed despite the low S/N. If due to Lyman alpha, this would correspond to a redshift of z~3.6. Our spectroscopic value is in agreement with the photometric redshift reported by Angulo et al. (GCN 42855). Given the low S/N over the continuum, we caution that this redshift solution should be considered tentative. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Stephane Favard, and the SOPHIE observer Felix Savoure. View this GCN Circular online at https://gcn.nasa.gov/circulars/42871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40939] GRB 251126A: further SAO RAS optical observations
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42870 SUBJECT: GRB 251126A: further SAO RAS optical observations DATE: 25/11/28 12:46:09 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), V. S. Shergin (SAO RAS), A. A. Volnova (IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN and GRB follow-up team. We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851; Page et al., GCN 42860) with the Zeiss-1000 1m telescope of the SAO RAS on November 27/28 night. We obtained two series of 300 sec. images in Rc band under a good weather conditions and seeing (FWHM) ~1".5. The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859; Volnova et al., GCN 42861; Breeveld and Caputo, GCN 42863; Gupta et al., GCN 42864; Burkhonov et al., GCN 42866; Maksut et al., GCN 42868) is clearly detected in the stacked frames. The preliminary results are as following. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-27 20:20:22 1.07076 11*300 Rc 22.02 0.04 24.1 2025-11-27 23:31:00 1.19809 8*300 Rc 22.24 0.07 23.8 The photometry is based on 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/42870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40938] GRB 250702B: detection of the compact radio counterpart 139 days after the burst
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42869 SUBJECT: GRB 250702B: detection of the compact radio counterpart 139 days after the burst DATE: 25/11/28 12:16:56 GMT FROM: ailing.wang.wal(a)gmail.com Ailing Wang (IHEP), Tao An, Yuanqi Liu (SHAO), Jinjun Geng, Songbo Zhang, Xuefeng Wu (PMO), Xinwen Shu (ANU) et al. report: We are conducting a multi-telescope, multi-epoch, multi-frequency radio campaign on GRB 250702BCD to trace its long-term afterglow evolution. Previous radio observations from other facilities have been reported by independent groups (e.g. GCNs 40983, 40985, 41053, 41059, 41061). Here we report results from Karl G. Jansky Very Large Array (VLA) observations on 2025 November 18 in B-array configuration. The data were calibrated and imaged with standard procedures in CASA. At C band (the central frequency of 6 GHz), we detect a radio source at the position of the known counterpart to GRB 250702B. The source is unresolved with a synthesized beam of 1.42 arcsec × 2.40 arcsec (PA = 28 deg) and has a peak flux density of ≈ 200 μJy beam⁻¹. The measured peak position is RA (J2000) = 18:58:45.5648 Dec (J2000) = -07:52:26.235 which is consistent with previously reported radio positions of the counterpart (GCN 41053). Complementary observations with eMERLIN and the European VLBI Network (EVN) in September yield flux densities consistent with the VLA measurement. This agreement indicates that the bulk of the radio emission, arising from long-lived synchrotron radiation (Levan et al. 2025, O'Connor et al. 2025), remains confined to a compact component on milliarcsecond to sub-arcsecond scales. This late-time detection at approximately 139 days after the 2025 July 2 trigger provides an important additional point on the radio light curve and confirms the persistence of a compact radio source. The full multi-epoch, multi-resolution dataset will be used to characterize the long-lived synchrotron emission and continued long-term monitoring is scheduled. We thank the TACs and operations staff of the VLA, eMERLIN, EVN, and ATCA for approving and supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40937] GRB 251126A NUTTelA-TAO Early Measurements
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42868 SUBJECT: GRB 251126A NUTTelA-TAO Early Measurements DATE: 25/11/28 10:49:00 GMT FROM: Zhanat Maksut at Nazarbayev University <zhanat.maksut(a)nu.edu.kz> Z. Maksut (NU), B. Grossan (UCB, NU), T. Komesh (NU), E. Abdikamalov (NU), M. Krugov (FAI) and D. Berdikhan (NU) The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 251126A on receipt of an automated GCN / BAT position alert, observing in Sloan g' and i' bands with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). Observations started at UT 2025 November 26, 19:11:32, 52 s after the SWIFT/BAT trigger (Caputo et al., GCN 42843). Weather conditions were good within the first 1 hour of observation, but gradually deteriorated to cloudy over the course of the night. A new optical counterpart reported by Swain et al., GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et al., GCN 42855; Pulido-Torres et al., GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859, was detected. We report the following preliminary, uncorrected, selected photometric values for the optical transient: tc-t0(s) t_exp i'(mag) err(mag) g’(mag) err(mag) -------- ------ ------- -------- 76 48.0 18.12 0.08 19.49 0.06 142 30.0 17.38 0.07 18.96 0.06 322 30.0 17.62 0.08 19.03 0.09 502 30.0 17.88 0.09 19.31 0.08 tc-t0 = trigger time minus image center time. Calibration was done with 5 bright Pan-STARRS catalog stars on our images (see Komesh, T. et al. 2023, MNRAS 520, 6104). We caution the reader that these are preliminary results, without color or other corrections, and will likely change. Please also note that times are approximate. Systematic errors are estimated from previous measurements. We welcome requests for additional data. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/42868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40936] LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42867 SUBJECT: LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates DATE: 25/11/28 08:15:18 GMT FROM: Mankeun Jeong <jmk5040(a)gmail.com> Mankeun Jeong, Myungshin Im, Seo-Won Chang, Hyeonho Choi (SNU/SNU ARC), Gregory S.-H. Paek (IfA), and Chung-Uk Lee (KASI), on behalf of the GECKO team We observed the S251112cm sky localization region (Updated; GCN 42690) following the LIGO/Virgo/KAGRA trigger. Optical imaging was obtained with the three 1.6-m Korea Microlensing Telescope Network (KMTNet) telescopes at CTIO, SAAO, and SSO, with most of the data taken from SSO. We surveyed the southern portion (decl. < -10 deg) of the S251112cm 90% localization region, covering ~1,012 deg^2 from 2025-11-13 to 2025-11-27. During the first three nights, we obtained R and I imaging with 480 sec total exposure per field (four dithered 120 sec exposures) over ~180 deg^2. For the remainder of the run, observations were conducted in R-band only with the same 480 sec per-field exposure. A fraction of the surveyed area overlaps with regions having KMTNet Synoptic Survey of the Southern Sky (KS4) reference images. Difference image analysis has been completed for ~60 deg^2, with additional processing ongoing. Below we list transient candidates re-identified from TNS and new GECKO sources detected in our imaging. Redshifts are adopted from the GLADE+ host-galaxy associations. Name | RA (deg) | Dec (deg) | R (AB mag) | I (AB mag) | Date-Obs (UTC) | Redshift -----|----------|-----------|------------|------------|-------------------|--------- AT2025aebs | 354.16948 | -33.01666 | 20.42 ± 0.05 | 20.66 ± 0.07 | 2025-11-16T12:24:50 | 0.1642 AT2025adbw | 3.31215 | -36.40843 | 19.07 ± 0.02 | — | 2025-11-14T14:23:37 | — AT2025abnc | 7.50565 | -34.96515 | 19.95 ± 0.05 | 20.54 ± 0.08 | 2025-11-14T12:40:10 | 0.1067 GECKO25dryb | 1.69517 | -33.38614 | 18.95 ± 0.01 | 19.05 ± 0.05 | 2025-11-14T13:39:42 | 0.2094 GECKO25drxk | 1.53192 | -35.03043 | 18.89 ± 0.01 | 18.86 ± 0.03 | 2025-11-14T13:39:42 | 0.2408 GECKO25dulp | 358.59508 | -35.91373 | 19.58 ± 0.06 | 18.65 ± 0.03 | 2025-11-16T13:40:59 | 0.0859 GECKO25dukb | 356.10091 | -34.07094 | 18.37 ± 0.01 | 18.13 ± 0.01 | 2025-11-16T12:24:50 | 0.1269 All newly identified GECKO candidates lie close to the center of the host galaxy, whose redshifts exceed the estimated distance of S251112cm, indicating they are unrelated to the GW event's physical origin. Further difference imaging and transient vetting across the remaining fields are underway. The GECKO network (Im et al. 2023; Paek et al. 2024) operates 0.5–1 m class telescopes worldwide for EM follow-up of gravitational-wave events. KMTNet is operated by the Korea Astronomy and Space Science Institute. We thank the KMTNet staff for their support during these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40935] GRB251126A: MAO/AZT-22 optical observations
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42866 SUBJECT: GRB251126A: MAO/AZT-22 optical observations DATE: 25/11/28 05:08:59 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> O. Burkhonov, Y. Rajabov, B.Abidkhanov, S. Ehgamberdiev, Y. Tillayev (UBAI), T. Boyqobilov, A. Shaymanov (Maidanak Observatory/UBAI) report on behalf of UBAI team. We observed the field of GRB 251126A detected by Swift (Caputo et al. 2025, GCN 42843) ), with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2025-11-27 at 22:17:50 UT, i.e, ~1.13 days after the Swift trigger. In total we obtained 6x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of GIT (Swain et al. 2025, GCN 42844). Our detection is consistent with Swain et al. 2025 (GCN 42844); Lipunov et al. 2025 (GCN 42847); Fu et al. 2025 (GCN 42848); Reguitti et al. 2025 (GCN 42849); Broens et al. 2025 (GCN 42850); Angulo et al. 2025 (GCN 42855); and Torres et al. 2025 (GCN 42856); Gupta et al. 2025 (GCN 42857); Cotter et al. 2025 (GCN 42858); Seki et al. 2025 (GCN 42859); Volnova et al. 2025 (GCN 42861); Breeveld et al. 2025 (GCN 42863); Gupta et al. 2025 (GCN 42864). Preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err. UL Site/Telescope (nxs) (mid, days) 2025-11-27 22:37:36 6x300 1.144 R 22.14 0.11 22.93 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. The data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40934] GRB 251128A: Fermi GBM Final Real-time Localization
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42865 SUBJECT: GRB 251128A: Fermi GBM Final Real-time Localization DATE: 25/11/28 04:33:00 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 04:22:21 UT on 28 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251128A (trigger 785996546.612178 / 251128182). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 117.5, Dec = 52.2 (J2000 degrees, equivalent to J2000 07h 49m, 52d 12'), with a statistical uncertainty of 2.0 degrees. The angle from the Fermi LAT boresight is 114.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40933] GRB251126A: Continued optical observation from 1.3m DFOT
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42864 SUBJECT: GRB251126A: Continued optical observation from 1.3m DFOT DATE: 25/11/28 01:22:33 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Debalina Kar, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB 251126A detected by Swift (Caputo et al. 2025, GCN 42843) 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 2025-11-27 at 18:10:19 UT, i.e., ~22.99 hours after the Swift trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of GIT (Swain et al. 2025, GCN 42844). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-27 18:10:19 ~22.99 R 300*12 21.62+/- 0.02 Our detection is consistent with Swain et al. 2025 (GCN 42844); Lipunov et al. 2025 (GCN 42847); Fu et al. 2025 (GCN 42848); Reguitti et al. 2025 (GCN 42849); Broens et al. 2025 (GCN 42850); Angulo et al. 2025 (GCN 42855); and Torres et al. 2025 (GCN 42856); Gupta et al. 2025 (GCN 42857); Cotter et al. 2025 (GCN 42858); Seki et al. 2025 (GCN 42859); Volnova et al. 2025 (GCN 42861); Breeveld et al. 2025 (GCN 42863). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40932] GRB 251126A: Swift/UVOT Detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42863 SUBJECT: GRB 251126A: Swift/UVOT Detection DATE: 25/11/27 14:51:12 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251126A 86s after the BAT trigger (Caputo et al., GCN Circ. 42843). The fading optical afterglow (Swain et al., GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et al., GCN 42855; Pulido-Torres et al., GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859 and Volnova et al., GCN 42861) is clearly detected in the initial UVOT exposures. The non detection in the U and UV filters is consistent with the redshift of z=3.5 found by Angulo et al., (GCN Circ. 42855). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 86 236 147 20.0 ± 0.1 white 579 772 39 20.3 ± 0.3 white 880 1377 186 20.5 ± 0.2 u_FC 299 548 246 >20.4 v 629 1080 58 18.7 ± 0.3 b 1159 1352 39 19.4 ± 0.3 uvw1 853 1467 35 >18.32 uvm2 653 847 39 >18.00 uvw2 778 1402 58 >18.70 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.063 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40931] EP251124a: Pan-STARRS ri-band imaging and photometry
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42862 SUBJECT: EP251124a: Pan-STARRS ri-band imaging and photometry DATE: 25/11/27 13:50:26 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> J. H. Gillanders (Oxford), M. Huber, K. C. Chambers (IfA, Univ. Hawaii), S. J. Smartt, K. W. Smith (Oxford/QUB), S. Srivastav (Oxford), M. Nicholl, D. Young, M. Fulton (QUB), T.-W. Chen (NCU, Taiwan) A. S. B. Schultz, T. de Boer, J. Fairlamb, G. Paek, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii). We observed the optical counterpart of EP251124a (Zhou et al., GCN 42816), using the Pan-STARRS telescope system (Chambers et al., 2016, arXiv e-prints, 1612.05560) on MJD 61004.36 (2025-11-25 08:38:24 UTC), 0.90 days after the EP-WXT detection (Zhou et al., GCN 42816). The Pan-STARRS system consists of 2x1.8m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy, and a broad w filter, which is a composite of the gri filters. Our observation consisted of 6x150s exposures in both the r and i filters with Pan-STARRS1. The images were processed with the Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target stacked images (Magnier et al., 2020a, ApJS, 251, 3; Magnier et al., 2020b, ApJS, 251, 6; Waters et al., 2020, ApJS, 251, 4). From these difference images, we do not detect any optical counterpart down to 3.5-sigma limiting AB magnitudes of r~22.3 and i~22.3. Our upper limits are in agreement with previously reported limits from Mohan et al. (GCN 42817), Wang et al. (GCN 42824), Lipunov et al. (GCN 42828), van Hoof et al. (GCN 42829), and Ma et al. (GCN 42833). View this GCN Circular online at https://gcn.nasa.gov/circulars/42862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40930] GRB 251126A: Mondy and SAO RAS optical observations
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42861 SUBJECT: GRB 251126A: Mondy and SAO RAS optical observations DATE: 25/11/27 13:38:15 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. S. Moskvitin (SAO RAS), V. P. Goranskij (SAI MSU, SAO RAS), E. Klunko (ISTP), V. S. Shergin (SAO RAS), N. Pankov (HSE, IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) in R-band and the Zeiss-1000 1m telescope of the SAO RAS in Rc-band on November 26/27 night. Observations with the AZT-33IK started at 20:35:11 UT (1.4097 hours after the trigger), observations with the Zeiss-1000 started at 21:31:39 UT (2.3508 hours after the trigger). The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al, GCN 42859) is clearly detected in individual frames. Preliminary photometry is given below. Date UT start t-T0 Exp. Filter OT Err. UL Seeing" Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-26 20:35:11 0.06221 5*120 R 19.99 0.08 21.1 5.0 Mondy/AZT-33IK 2025-11-26 20:45:12 0.07125 8*120 R 19.84 0.07 21.4 5.0 Mondy/AZT-33IK 2025-11-26 21:01:12 0.08584 13*120 R 19.89 0.06 21.7 5.0 Mondy/AZT-33IK 2025-11-26 21:31:39 0.10164 2*300 Rc 19.81 0.08 21.2 2.2 SAO/Zeiss-1000 2025-11-26 21:58:22 0.12230 3*300 Rc 19.95 0.03 22.7 2.0 SAO/Zeiss-1000 2025-11-27 01:14:02 0.25960 2*600 Rc 20.63 0.04 23.2 1.6 SAO/Zeiss-1000 2025-11-27 01:57:56 0.29372 3*600 Rc 20.62 0.03 23.4 1.6 SAO/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/42861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40929] GRB 251126A: Swift-XRT refined Analysis
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42860 SUBJECT: GRB 251126A: Swift-XRT refined Analysis DATE: 25/11/27 13:02:50 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.2 ks of XRT data for GRB 251126A, from 66 s to 56.7 ks after the trigger. The data comprise 9 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 a series of power-law decays. The initial decay index is alpha=3.5 (+0.6, -0.5). At T+210 s the decay flattens to an alpha of -0.50 (+0.00, -0.17) before breaking again at T+1954 s to a final decay with index alpha=1.13 (+0.21, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.11 (+0.25, -0.24). The best-fitting absorption column is 1.7 (+0.8, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 9.5 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 3.3 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 9.5 x 10^20 cm^-2 Excess significance: 1.8 sigma Photon index: 2.11 (+0.25, -0.24) If the light curve continues to decay with a power-law decay index of 1.13, the count rate at T+24 hours will be 8.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-13 (3.9 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01417793. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40928] GRB 251126A : MITSuME Akeno optical afterglow candidate detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42859 SUBJECT: GRB 251126A : MITSuME Akeno optical afterglow candidate detection DATE: 25/11/27 12:08:00 GMT FROM: seki(a)hp.phys.titech.ac.jp H. Seki, I. Takahashi, M. Sasada, Y. Kubo, H. Hagio, A. Ochi, R. Kato, S. Joshima, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 251126A detected by Swift (Caputo et al., GCN 42843) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2025-11-26 19:11:15 UT (39 seconds after the trigger). We stacked the images taken under good conditions. We detected a point source in the g'-, Rc- and Ic-band images at a position of the reported optical candidate (Swain et al., GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et al., GCN 42855; Pulido-Torres et al., GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858). Here we report the magnitudes of the source as follows. T0+[sec] | MID-UT | T-EXP[sec] | magnitudes --------------------------------------------------------------------------------------------------------------- 1310 | 2025-11-26 19:32:26 | 1560 | g'=20.5+/-0.3, Rc=18.7+/-0.1, Ic=18.2+/-0.1 --------------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the trigger T-EXP: Total exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire) View this GCN Circular online at https://gcn.nasa.gov/circulars/42859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40927] GRB 251126A: NOT optical observations
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42858 SUBJECT: GRB 251126A: NOT optical observations DATE: 25/11/27 11:11:11 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> L. Cotter (UCD), A. Martin-Carrillo (UCD), S.Y. Fu (HUST), J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), T. Pursimo (NOT) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 251126A (Caputo et al., GCN 42843) with the Nordic Telescope (NOT) equipped with the ALFOSC Camera. We obtained 3x300s r-band images with observations starting on 2025-11-26 at 23:31:36 UTC, under good seeing (~1”). However, unfortunately, observations had to be interrupted due to adverse weather conditions. The optical counterpart reported by Swain et al. (GCN 42844), Lipunov et al. (GCN 42847), Fu et al. (GCN 42848), Reguitti et al. (GCN 42849), Broens et al. (GCN 42850), Angulo et al. (GCN 42855), Torres et al. (GCN 42856) and Gupta et al. (GCN 42857) is well detected in our stacked image with an AB magnitude of r = 20.72 ± 0.05 at a mid epoch of 2025-11-26 23:34:06.554 (4.4 hr after the Swift/BAT trigger). This magnitude was calibrated against nearby objects from the Pan-STARRS catalog and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40926] GRB 251126A: 1.3m DFOT optical afterglow detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42857 SUBJECT: GRB 251126A: 1.3m DFOT optical afterglow detection DATE: 25/11/27 08:14:19 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 251126A detected by Swift (Caputo et al. 2025, GCN 42843) 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 2025-11-26 at 22:17:19 UT, i.e., ~3.11 hour after the Swift 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 the optical counterpart in our stacked image within the error box of GIT (Swain et al. 2025, GCN 42844). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-26 22:17:19 ~3.11 I 300*12 19.41+/- 0.01 Our detection is consistent with Swain et al. 2025 (GCN 42844); Lipunov et al. 2025 (GCN 42847); Fu et al. 2025 (GCN 42848); Reguitti et al. 2025 (GCN 42849); Broens et al. 2025 (GCN 42850); Angulo et al. 2025 (GCN 42855); and Torres et al. 2025 (GCN 42856). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40925] GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42856 SUBJECT: GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory DATE: 25/11/27 06:40:21 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> M. Pulido-Torres, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, L. Juliá-Maroto, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez, E. Urquijo-Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). Following the detection of the Swift GRB 251126A (Caputo et al., GCN Circ. 42843; Evans et al., GCN Circ. 42845; and Goad et al., GCN Circ. 42851), 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 McDonald Observatory, Texas. The observation, a single exposure of 300 sec in the SDSS r' filter, started on 2025-11-27 at 04:41:19 UT, about 9.51 hours after the Swift trigger. The optical counterpart first detected by the GROWTH-India Telescope (GIT) (Swain et al., GCN Circ. 42844) is clearly detected in our image with a magnitude of r' = 20.86 +/- 0.13 (AB), calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical observations: Swain et al. (GCN Circ. 42844), Lipunov et al. (GCN Circ. 42847), Fu et al. (GCN Circ. 42848), Reguitti et al. (GCN Circ. 42849), Broens et al. (GCN Circ. 42850), and Angulo et al. (GCN Circ. 42855). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-010). These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain). 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/42856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40924] GRB 251126A: COLIBRÍ photometric redshift z = 3.5
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42855 SUBJECT: GRB 251126A: COLIBRÍ photometric redshift z = 3.5 DATE: 25/11/27 04:57:59 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), 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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Swift GRB 251126A (Caputo et al., GCN Circ. 42843) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-27 02:49 to 04:14 UTC (from 7.6 to 9.1 hours after the trigger) and obtained, respectively, 10, 27, 11, 23, and 23 minutes of exposure in the g, r, i, z, and y filters. 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. We detected the optical counterpart reported by Swain et al. (GCN Circ. 42844), Lipunov et al. (GCN Circ. 42847), Fu et al. (GCN Circ. 42848), Reguitti et al. (GCN Circ. 42849), and Broens et al. (GCN Circ. 42850) at preliminary magnitudes of: r = 20.62 +/- 0.05 z = 19.86 +/- 0.07 In our data, we see a clear break in the spectrum in g. After correcting for the Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.063 mag (Schlafly & Finkbeiner 2011) and fitting a power-law model to the grizy-bands with SMC extinction, we derive a photometric redshift of z = 3.52 (+0.18, -0.20, 1-sigma confidence interval). Further observations are ongoing. 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/42855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40923] GRB 251125B: GECAM-B detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42854 SUBJECT: GRB 251125B: GECAM-B detection DATE: 25/11/27 04:41:58 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst, GRB 251125B, at 2025-11-25T20:23:45.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #42836). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a pulse with a duration (T90) of 8.5 +2.0/-3.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251125B.png The time-averaged spectrum from T0-0.8 s to T0+9.3 s is best fitted by a power law function. The power law index is -1.36 +0.06/-0.05. The event fluence (10-1000 keV) in this time interval is (2.86 +0.34/-0.31)E-06 erg/cm^2. 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/42854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40922] Fermi GRB 251127A: Global MASTER-Net observations report
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42853 SUBJECT: Fermi GRB 251127A: Global MASTER-Net observations report DATE: 25/11/27 03:30:35 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 251127A ( Fermi GBM team, GCN 42852) errorbox 26 sec after notice time and 61 sec after trigger time at 2025-11-27 03:18:44 UT, with upper limit up to 16.6 mag. Observations started at twilight. The observations began at zenith distance = 14 deg. The sun altitude is -10.6 deg. The galactic latitude b = 58 deg., longitude l = 199 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3052815 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 67 | 2025-11-27 03:18:44 | MASTER-Kislovodsk | (10h 26m 49.07s , +29d 21m 07.8s) | C | 10 | 15.7 | 67 | 2025-11-27 03:18:44 | MASTER-Kislovodsk | (10h 21m 41.55s , +29d 42m 18.9s) | C | 10 | 14.2 | 96 | 2025-11-27 03:19:13 | MASTER-Kislovodsk | (10h 26m 49.14s , +29d 21m 07.1s) | C | 10 | 15.7 | 96 | 2025-11-27 03:19:14 | MASTER-Kislovodsk | (10h 21m 41.27s , +29d 42m 13.3s) | C | 10 | 14.1 | 144 | 2025-11-27 03:19:52 | MASTER-Kislovodsk | (10h 28m 11.83s , +32d 30m 38.8s) | C | 30 | 16.6 | 144 | 2025-11-27 03:19:52 | MASTER-Kislovodsk | (10h 22m 52.53s , +32d 52m 02.7s) | C | 30 | 15.4 | 194 | 2025-11-27 03:20:42 | MASTER-Kislovodsk | (10h 22m 52.49s , +32d 52m 02.0s) | C | 30 | 15.2 | 194 | 2025-11-27 03:20:42 | MASTER-Kislovodsk | (10h 28m 11.82s , +32d 30m 38.3s) | C | 30 | 16.4 | 249 | 2025-11-27 03:21:31 | MASTER-Kislovodsk | (10h 22m 52.28s , +32d 51m 59.6s) | C | 40 | 15.4 | 249 | 2025-11-27 03:21:31 | MASTER-Kislovodsk | (10h 28m 11.77s , +32d 30m 37.9s) | C | 40 | 16.6 | 314 | 2025-11-27 03:22:31 | MASTER-Kislovodsk | (10h 28m 11.71s , +32d 30m 37.2s) | C | 50 | 16.4 | 314 | 2025-11-27 03:22:31 | MASTER-Kislovodsk | (10h 22m 52.22s , +32d 51m 59.0s) | C | 50 | 15.1 | 394 | 2025-11-27 03:23:41 | MASTER-Kislovodsk | (10h 22m 51.99s , +32d 51m 57.2s) | C | 70 | 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/42853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40921] GRB 251127A: Fermi GBM Final Real-time Localization
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42852 SUBJECT: GRB 251127A: Fermi GBM Final Real-time Localization DATE: 25/11/27 03:28:10 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 03:17:42 UT on 27 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251127A (trigger 785906267.770746 / 251127137). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 155.6, Dec = 30.2 (J2000 degrees, equivalent to J2000 10h 22m, 30d 11'), with a statistical uncertainty of 4.1 degrees. The angle from the Fermi LAT boresight is 24.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251127137/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251127137/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251127137/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40920] GRB 251126A: Enhanced Swift-XRT position
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42851 SUBJECT: GRB 251126A: Enhanced Swift-XRT position DATE: 25/11/27 01:31:57 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 633 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251126A, 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 = 99.94120, +54.98588 which is equivalent to: RA (J2000): 06h 39m 45.89s Dec (J2000): +54d 59' 09.2" with an uncertainty of 4.5 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/42851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40919] GRB 251126A: Kilonova-Catcher optical afterglow detection
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42850 SUBJECT: GRB 251126A: Kilonova-Catcher optical afterglow detection DATE: 25/11/26 21:24:46 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> E. Broens (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251126A detected by Swift (Caputo et al., GCN 42843) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a private telescope T-BRO operated by E. Broens. Our observations started at TGRB+35 min and were taken unfiltered. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we marginally detect the optical counterpart reported by GIT (Swain, GCN 42844). Despite the pretty low SNR (while the source is visible by eye in our image), we performed a forced photometry at the position we found to be at RA, Dec (J2000): 99.9440, +54.9864. We report our follow-up results in the table below: +---------------+-----------+---------+----------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+=========+================+=============+ | 0.83 | 10 x 180s | r (AB) | 19.43 +/- 0.42 | T-BRO | +---------------+-----------+---------+----------------+-------------+ Compared to the magnitude reported by GIT (Swain, GCN 42844) the source has significantly faded even when considering our marginal detection which induced large error bars on the source photometry. Therefore, we confirm that this source is likely the optical afterglow of GRB 251126A. This is in agreement with the detections also reported by the Nanshan/HMT team (Fu et al., GCN 42848) and the Asiago team (Reguitti et al., GCN 42849). All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Clear filters were calibrated using the PanSTARRS DR1 catalog using the PS1-r filter. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40918] GRB 251126A: Asiago i-band detection
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42849 SUBJECT: GRB 251126A: Asiago i-band detection DATE: 25/11/26 21:14:37 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. Reguitti (INAF/OAPD), L. Tomasella (INAF/OAPD), D. B. Malesani (DAWN/NIB and Radboud), report on behalf of a larger collaboration: We observed the optical afterglow (Swain et al., GCN 42844; Fu et al., GCN 42848) of GRB 251126A (Caputo et al., GCN 42843) using the 67/92 Schmidt Telescope located at the Asiago observatory (Italy). Observations were carried out using the Sloan i filter. In a single exposure with start time 2025 Nov 26.8252 UT (37.8 min after the Swift/BAT trigger), the afterglow is detected with a magnitude i = 18.27 +- 0.15 (AB), calibrated against nearby stars fron the Pan-STARRS catalog, and not corrected for Galactic extinction. Compared to the earlier optical measurements (Swain et al., GCN 42844; Fu et al., GCN 42848), our images seem to indicate a red r-i color for the optical afterglow. View this GCN Circular online at https://gcn.nasa.gov/circulars/42849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40917] GRB 251126A: Nanshan/HMT optical afterglow detection
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42848 SUBJECT: GRB 251126A: Nanshan/HMT optical afterglow detection DATE: 25/11/26 21:01:26 GMT FROM: syfu(a)nao.cas.cn S.Y. Fu (HUST), S.Q. Jiang, J. An, X. Liu, L.B. He, Z.P. Zhu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 251126A detected by Swift/BAT (Caputo et al., GCN 42843) using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 19:11:52 UT on 2025-11-26, i.e., 76 seconds after the Swift/BAT trigger, and a series of unfiltered frames with different exposures were obtained. An uncatalogued and varying optical source is detected within the XRT error circle (Caputo et al., GCN 42843) at coordinates: R.A.(J2000) = 06:39:46.56 Dec.(J2000) = +54:59:12.27 with an uncertainty of ~0.5 arcsec. This position is consistent with the previous report by GIT (Swain, GCN 42844). The source has ~ 19.0 mag in the first image, calibrated with the nearby Pan-STARRS field and not corrected for Galactic extinction. The early light curve initially shows a slow rise, reaching a peak at ~150s, and then decays with power law index of ~0.5. Thus, we conclude that the source is the afterglow of GRB 251126A. Observations are still ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/42848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40916] Swift GRB 251126A: Global MASTER-Net observations report
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42847 SUBJECT: Swift GRB 251126A: Global MASTER-Net observations report DATE: 25/11/26 20:34:46 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) was pointed to the Swift GRB 251126A ( R. Caputo et al., GCN 42843) errorbox 4521 sec after notice time and 4538 sec after trigger time at 2025-11-26 20:26:15 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 31 deg. The sun altitude is -67.1 deg. The galactic latitude b = 21 deg., longitude l = 161 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3052530 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 4629 | MASTER-Kislovodsk | C | 180 | 15.7 | 4629 | MASTER-Kislovodsk | C | 180 | 18.4 | 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/42847. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40915] GRB 251121A: Fermi GBM Observation
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42846 SUBJECT: GRB 251121A: Fermi GBM Observation DATE: 25/11/26 20:32:32 GMT FROM: Angus Jameson <abj0023(a)uah.edu> S. Bala (USRA), A. Jameson (UAH), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:30:58.99 UT on 21 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251121A (trigger 785435463/251121688), which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025 GCN 42795). The Fermi GBM on-ground location (GCN 42790) is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 100 degrees. The GBM light curve single peak with a duration (T90) of about 0.3 s (50-300 keV). The time-averaged spectrum from T0-0.2 to T0+0.3 s is best fit by a simple power law function with index -1.31 +/- 0.07. The event fluence (10-1000 keV) in this time interval is (2.8 +/- 0.3)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 5 +/- 1 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/42846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40914] GRB 251126A: Prompt enhanced Swift-XRT position
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42845 SUBJECT: GRB 251126A: Prompt enhanced Swift-XRT position DATE: 25/11/26 19:53:46 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-XRT team: Using 1.4 ks of promptly downlinked XRT event data for GRB 251126A, we find an enhanced XRT position of the afterglow: RA, Dec: 99.94311, 54.98585 which is equivalent to: RA (J2000) = 06 39 46.35 Dec (J2000) = +54 59 09.1 with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1417793. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40913] GRB 251126A: GIT discovery of the likely optical afterglow
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42844 SUBJECT: GRB 251126A: GIT discovery of the likely optical afterglow DATE: 25/11/26 19:41:15 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> We observed the field of GRB 251126A detected by Swift (Caputo et al., GCN 42843) with 0.7m GROWTH-India Telescope (GIT). We started observations at 19:14:32 UT, i.e., 3.93 mins after the Swift/BAT trigger. We obtained multiple frames in the r' band of 360 sec each. We detected an uncatalogued source at RA 06:39:46.42, Dec: +54:59:11.78 with an uncertainty of 0.4 arcsec. There is no minor planet present at this position. The photometric results follow as: | JD (mid) | tmid-t0 (mins) | Filter | Exposure (s) | Mag (AB) | | ------------- | ----------- | ------ | ------------ | -------------- | | 2461006.3017592593 | 3.93 | r' | 360 | 18.26 +- 0.06 | We encourage photometric for further confirmation and spectroscopic follow-up for redshift measurement. The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40912] GRB 251126A: Swift detection of a burst
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42843 SUBJECT: GRB 251126A: Swift detection of a burst DATE: 25/11/26 19:26:44 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. Caputo (GSFC), M. J. Moss (GSFC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:10:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251126A (trigger=1417793). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 99.910, +54.987 which is RA(J2000) = 06h 39m 39s Dec(J2000) = +54d 59' 13" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 20 sec. The peak count rate was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 19:11:58.3 UT, 81.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 99.94124, 54.98591 which is equivalent to: RA(J2000) = 06h 39m 45.90s Dec(J2000) = +54d 59' 09.3" with an uncertainty of 4.4 arcseconds (radius, 90% containment). This location is 64 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. No spectrum from the promptly downlinked event data is yet available to determine the column density. There are no UVOT data available at this time. Analysis will be reported at a later time. Burst Advocate for this burst is R. Caputo (regina.caputo AT nasa.gov) 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/42843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40911] GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42842 SUBJECT: GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3 DATE: 25/11/26 16:30:16 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Jean-Grégoire Ducoin (CPPM), Noémie Globus (UNAM), N. A. Rakotondrainibe (LAM), 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), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We reobserved the field of the MASTER OT J155558.56+581224.1 candidate afterglow (Gress et al., GCN Circ. 42838) of the Fermi GRB 251125B (Fermi GBM team., GCN Circ. 42836) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-26 11:44 to 13:00 UTC (from 15.34 to 16.60 hours after the trigger) and obtained 20 minutes of exposure in each of the g, r, and i filters and 60 minutes of simultaneous exposure in the z filter. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. Compared to our first epoch of observations (Globus et al., GCN Circ. 42840), the afterglow has continued to fade. After correcting for the Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.013 mag (Schlafly & Finkbeiner 2011) and fitting a power-law with a no-dust extinction model to the griz-bands, we estimate a photometric redshift upper limit of z < 3. We therefore encourage follow-up observations. 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/42842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40910] EP251124b follow-up observation by EP-FXT
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42841 SUBJECT: EP251124b follow-up observation by EP-FXT DATE: 25/11/26 10:26:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B. Zhang, J. P. Feng (USTC), D. F. Hu (PMO, CAS), H. Sun, H. N. Yang (NAO, CAS), Z. C. Zou (NJU) on behalf of the Einstein Probe (EP) team: We performed a Target-of-Opportunity observation with the Follow-up X-ray Telescope on board the Einstein Probe (EP) for EP251124b (Feng et al, GCN 42834), which was also followed by Lipunov et al. (GCN #42835) and van Hoof et al. (GCN #42839). The observation began at 2025-11-25T22:12:00 (UTC) with an exposure time of about 1790 seconds. An uncatalogued X-ray source was detected within the WXT error circle at R.A. = 93.4802 deg, DEC = 52.7313 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. including both statistical and systematic uncertainties). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.5 x 10^21 cm^-2 and a photon index of 0.97 (-0.84, +0.93). The derived average unabsorbed 0.5-10 keV flux is 9.02 (-5.33, +13.9) x 10^(-13) 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/42841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40909] GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42840 SUBJECT: GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate DATE: 25/11/26 05:51:53 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Nathaniel R. Butler (ASU), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the MASTER OT J155558.56+581224.1 candidate afterglow (Gress et al., GCN Circ. 42838) of the Fermi GRB 251125B (Fermi GBM team., GCN Circ. 42836) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-26 01:36 to 02:39 UTC (median epoch 5.73 hours after the trigger) and obtained 48 minutes of simultaneous exposure in each of the r and z filters. 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 detect the optical candidate at preliminary magnitudes of: r = 20.46 +/- 0.02 z = 20.17 +/- 0.05 The source has faded considerably since the observation of Gress et al. (GCN Circ 42838), which confirms that it is likely to be the afterglow of the GRB. Further observations are planned. 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/42840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40908] EP251124b: NOT r- and z-band optical upper limits
by GCN Circulars 26 Nov '25

26 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42839 SUBJECT: EP251124b: NOT r- and z-band optical upper limits DATE: 25/11/26 00:24:55 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), G. Corcoran (UCD), J. N. D. van Dalen, A. Martin-Carrillo (UCD), D. Xu (NAOC), S.Q. Jiang (NAO, CAS), T. Pursimo (NOT, Aarhus University), J.P.U. Fynbo (DAWN/NBI), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP251124b (Feng et al., GCN 42834) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (5x200 s) bands, starting on 2025-11-25 at 22:19:58.38 UTC (1.2 days after the WXT trigger). No new source is detected within the EP/WXT uncertainty region (Feng et al., GCN 42834). From the stacked images we obtain the following 3-sigma upper limits: r > 24.4 z > 23.2 These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. We also performed image subtraction in r band using a reference image from the Legacy Survey. No new source is revealed compared to the reference. However, we note that there are artefacts across the field. View this GCN Circular online at https://gcn.nasa.gov/circulars/42839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40907] Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42838 SUBJECT: Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery DATE: 25/11/25 23:04:15 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> O.A.Gress, N.M.Budnev (Irkutsk State University), V.M. Lipunov, A.Kuznetsov, I.Panchenko, E.Gorbovskoy, G.Antipov, P.Balanutsa, V.Senik, I.Panchenko, N. Tiurina, K.Zhirkov, Ya.Kechin, A.Chasovnikov, V.Topolev, D.Vlasenko, Yu. Tselik(Lomonosov MSU, SAI, Moscow), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D. Buckley (SAAO, South Africa), O.Ershova (Irkutsk State University), 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-Tunka robotic telescope (Global MASTER-Net [1-4], http://observ.pereplet.ru) started inspect (Lipunov et al. GCN 42837) of Fermi GRB 251125B ( GCN 42836) at MASTER-Tunka and MASTER-Kislovodsk. MASTER auto-detection system discovered optical counterpart of this GRB MASTER OT J155558.56+581224.1 with unfiltered m_OT=18.2 at 2025-11-25 20:34:32UT with typical for GRB light curve with decay. https://www.wis-tns.org/object/2025aevl Real time updated cover map and discovered OT position is available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051835 Observations and data analysis will be continued. [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/42838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40906] Fermi GRB 251125B: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42837 SUBJECT: Fermi GRB 251125B: Global MASTER-Net observations report DATE: 25/11/25 20:45:36 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 251125B ( Fermi GBM team, GCN 42836) errorbox 37 sec after notice time and 71 sec after trigger time at 2025-11-25 20:24:57 UT, with upper limit up to 19.8 mag. The observations began at zenith distance = 62 deg. The sun altitude is -39.2 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251125B errorbox 40 sec after notice time and 74 sec after trigger time at 2025-11-25 20:25:00 UT, with upper limit up to 13.2 mag. The observations began at zenith distance = 79 deg. The sun altitude is -66.8 deg. The galactic latitude b = 46 deg., longitude l = 89 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051835 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 76 | 2025-11-25 20:24:57 | MASTER-Tunka | (15h 49m 53.68s , +58d 02m 46.1s) | C | 10 | 19.0 | 77 | 2025-11-25 20:24:57 | MASTER- | (15h 50m 33.82s , +57d 56m 14.3s) | C | 10 | 18.9 | 80 | 2025-11-25 20:25:00 | MASTER-Kislovodsk | (15h 48m 55.38s , +57d 57m 14.7s) | C | 10 | 12.3 | 81 | 2025-11-25 20:25:01 | MASTER-Kislovodsk | (15h 41m 25.24s , +58d 17m 41.9s) | C | 10 | 12.3 | 613 | 2025-11-25 20:33:29 | MASTER-Tunka | (15h 50m 14.31s , +57d 20m 48.8s) | C | 60 | 19.0 | 673 | 2025-11-25 20:33:29 | MASTER-Tunka | (15h 50m 14.31s , +57d 20m 48.8s) | C | 180 | 19.8 | Coadd 613 | 2025-11-25 20:33:29 | MASTER- | (15h 50m 55.15s , +57d 14m 04.0s) | C | 60 | 18.9 | 649 | 2025-11-25 20:33:35 | MASTER-Kislovodsk | (15h 49m 05.73s , +57d 13m 41.7s) | C | 120 | 12.9 | 677 | 2025-11-25 20:34:32 | MASTER-Tunka | (15h 50m 14.11s , +57d 20m 48.0s) | C | 60 | 19.2 | 677 | 2025-11-25 20:34:32 | MASTER- | (15h 50m 55.07s , +57d 14m 02.7s) | C | 60 | 19.1 | 740 | 2025-11-25 20:35:36 | MASTER-Tunka | (15h 50m 13.87s , +57d 20m 46.9s) | C | 60 | 18.9 | 740 | 2025-11-25 20:35:36 | MASTER- | (15h 50m 54.92s , +57d 14m 02.1s) | C | 60 | 18.7 | 789 | 2025-11-25 20:35:54 | MASTER-Kislovodsk | (15h 49m 06.58s , +57d 13m 30.8s) | C | 120 | 13.2 | 803 | 2025-11-25 20:36:39 | MASTER-Tunka | (15h 50m 13.66s , +57d 20m 45.9s) | C | 60 | 19.5 | 804 | 2025-11-25 20:36:39 | MASTER- | (15h 50m 54.78s , +57d 14m 01.8s) | C | 60 | 19.3 | 928 | 2025-11-25 20:38:14 | MASTER-Kislovodsk | (15h 49m 07.46s , +57d 13m 23.9s) | C | 120 | 13.1 | 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/42837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40905] GRB 251125B: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42836 SUBJECT: GRB 251125B: Fermi GBM Final Real-time Localization DATE: 25/11/25 20:34:30 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 20:23:45 UT on 25 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251125B (trigger 785795030.880336 / 251125850). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 237.5, Dec = 57.5 (J2000 degrees, equivalent to J2000 15h 50m, 57d 30'), with a statistical uncertainty of 3.1 degrees. The angle from the Fermi LAT boresight is 45.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40904] EP251124b: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42835 SUBJECT: EP251124b: Global MASTER-Net observations report DATE: 25/11/25 15:54:29 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 EP251124b ( EP Team et al., GCN 42834) errorbox 186 sec after notice time and 80214 sec after trigger time at 2025-11-25 15:39:56 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 68 deg. The sun altitude is -21.6 deg. The galactic latitude b = 17 deg., longitude l = 162 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051627 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 80245 | 2025-11-25 15:39:56 | MASTER-Kislovodsk | (06h 13m 18.49s , +52d 39m 59.0s) | C | 60 | 15.3 | 80245 | 2025-11-25 15:39:56 | MASTER-Kislovodsk | (06h 13m 25.72s , +52d 17m 24.8s) | 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/42835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40903] EP251124b: EP-WXT detection of a fast X-ray transient
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42834 SUBJECT: EP251124b: EP-WXT detection of a fast X-ray transient DATE: 25/11/25 15:33:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Feng, B. Zhang (USTC), X. X. Sun (NAO, CAS), Q. C. Liu (THU), D. F. Hu, Y. L. Hua (PMO, CAS), C. C. Jin (NAO, CAS), 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 EP251124b. The transient was detected by EP-WXT at 2025-11-24T17:23:02 (UTC). The WXT position of the source is R.A. = 93.493 deg, DEC = 52.694 deg (J2000) with an uncertainty of 2.6 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for ～240 seconds, the average 0.5-4 keV spectrum can be fitted with an absorbed power-law model, with fixed galactic nH of 1.51 x 10^21 cm^-2 and a photon index of 1.72 (-0.78, +0.83). The unabsorbed average 0.5-4 keV flux is estimated to be 2.97 (-0.95, +1.51) x 10^-10 erg/s/cm2. The peak flux reaches around 4.8e-9 erg/s/cm2. The uncertainties are at the 90% confidence level for the above parameters. The transient was discovered by the ground analysis of the delayed telemetry data. The follow-up observation of EP-FXT has been scheduled. 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/42834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40902] EP251124a: Xinglong GWAC-F60A optical observation
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42833 SUBJECT: EP251124a: Xinglong GWAC-F60A optical observation DATE: 25/11/25 09:48:40 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, X. H. Han, P. P. Zhang, H. L. Li, Z. H. Yao, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team: We observed the field of EP251124a triggered by EP/WXT (Zhou et al., GCN 42816; GCN 42832) using the GWAC-F60A telescope located at Xinglong observatory, China. We obtained a series of frames in R-band, starting at 2025-11-24T11:22:30 UTC, about 12.42 minutes after the trigger. No uncataloged sources were detected in our single or stacked images within the error box provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827), the three sigma limit is: mid-time | exposure time | band | upper limit ----------- -|-----------------|-------|------------- 19.5 minutes | 10*50 sec | R | 19.5 mag None of the known sources showed significant brightness variations within EP/FXT and Swift/XRT errorbox compared with USNO-B1.0 catalog. Our results are consistent with GIT (Mohan et al., GCN 42817), Kinder (Wang et al., GCN 42824), MASTER (Lipunov et al., GCN 42828), and NOT (van Hoof et al., GCN 42829). Our photometry was 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/42833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40901] EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42832 SUBJECT: EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7 DATE: 25/11/25 09:23:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Zhou (PMO, CAS), J.-Y. Cao (IHEP), H.-N. Yang, and Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: Refined analysis of the WXT data shows that EP251124a (GCN #42816) is associated with the Cluster of Galaxies AWM 7. The estimated flux is ~6.17e-11 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/42832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40900] Fermi GRB 251125A: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42831 SUBJECT: Fermi GRB 251125A: Global MASTER-Net observations report DATE: 25/11/25 01:15:21 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) started inspect of the Fermi GRB 251125A ( Fermi GBM team, GCN 42830) errorbox 29 sec after notice time and 35 sec after trigger time at 2025-11-25 01:00:14 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 58 deg. The sun altitude is -35.2 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251125A errorbox 58 sec after notice time and 64 sec after trigger time at 2025-11-25 01:00:43 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 65 deg. The sun altitude is -25.5 deg. The galactic latitude b = 44 deg., longitude l = 259 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051146 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40 | 2025-11-25 01:00:14 | MASTER-Kislovodsk | (10h 47m 41.84s , -02d 16m 18.0s) | C | 10 | 16.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 57.0s) | C | 10 | 17.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 48m 05.24s , -02d 41m 35.6s) | C | 10 | 17.7 | 70 | 2025-11-25 01:00:44 | MASTER-Kislovodsk | (10h 47m 41.88s , -02d 16m 25.2s) | C | 10 | 16.7 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 46m 14.21s , -02d 25m 59.4s) | C | 20 | 18.1 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 35.0s) | C | 20 | 18.5 | 106 | 2025-11-25 01:01:14 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 40.7s) | C | 20 | 17.2 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 46m 14.28s , -02d 25m 58.7s) | C | 30 | 18.5 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 48m 05.23s , -02d 41m 33.9s) | C | 30 | 18.8 | 146 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.97s , -02d 16m 43.6s) | C | 20 | 17.2 | 181 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.96s , -02d 16m 43.7s) | C | 90 | 18.2 | Coadd 195 | 2025-11-25 01:02:38 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 44.6s) | C | 30 | 17.5 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 46m 14.26s , -02d 25m 58.4s) | C | 40 | 18.8 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 33.1s) | C | 40 | 18.9 | 250 | 2025-11-25 01:03:28 | MASTER-Kislovodsk | (10h 47m 41.92s , -02d 16m 45.1s) | C | 40 | 17.8 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 58.5s) | C | 50 | 18.9 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 48m 05.17s , -02d 41m 32.9s) | C | 50 | 19.0 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 47m 41.90s , -02d 16m 45.0s) | C | 50 | 17.8 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 52m 01.99s , -02d 40m 47.8s) | C | 50 | 12.0 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 46m 14.20s , -02d 25m 58.8s) | C | 60 | 19.1 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 48m 05.12s , -02d 41m 32.9s) | C | 60 | 19.3 | 395 | 2025-11-25 01:05:38 | MASTER-Kislovodsk | (10h 47m 41.86s , -02d 16m 44.4s) | C | 70 | 18.1 | 480 | 2025-11-25 01:07:08 | MASTER-Kislovodsk | (10h 51m 53.78s , -02d 19m 53.0s) | C | 60 | 17.8 | 560 | 2025-11-25 01:08:28 | MASTER-Kislovodsk | (10h 51m 23.73s , -00d 26m 51.2s) | C | 60 | 18.0 | 639 | 2025-11-25 01:09:48 | MASTER-Kislovodsk | (10h 36m 38.70s , -02d 21m 11.9s) | C | 60 | 17.0 | 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/42831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40899] GRB 251125A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42830 SUBJECT: GRB 251125A: Fermi GBM Final Real-time Localization DATE: 25/11/25 01:09:58 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 00:59:38 UT on 25 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251125A (trigger 785725183.783164 / 251125041). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 161.9, Dec = -7.6 (J2000 degrees, equivalent to J2000 10h 47m, -7d 35'), with a statistical uncertainty of 7.6 degrees. The angle from the Fermi LAT boresight is 37.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40898] EP251124a: NOT r- and z-band optical upper limits
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42829 SUBJECT: EP251124a: NOT r- and z-band optical upper limits DATE: 25/11/24 23:32:52 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. N. D. van Dalen (Radboud), P. G. Jonker (Radboud), Shilpa Bijavara Seshashayana (NOT and Malmo Univ.), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP251124a (Zhou et al., GCN 42816) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (3x200 s) bands, starting on 2025-11-24 at 21:34:32 UTC (10.4 hr after the WXT trigger). No new source is detected within any of the X-ray error circles provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827). From the stacked images we obtain the following 3-sigma upper limits: r > 24.4 z > 23.0 These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. The upper limits are consistent with previously reported upper limits in r-band (Mohan et al., GCN 42817; Wang et al., GCN 42824). View this GCN Circular online at https://gcn.nasa.gov/circulars/42829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40897] EP251124a: Global MASTER-Net observations report
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42828 SUBJECT: EP251124a: Global MASTER-Net observations report DATE: 25/11/24 21:09:29 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 EP251124a ( EP Team et al., GCN 42816) errorbox 21097 sec after notice time and 28845 sec after trigger time at 2025-11-24 19:10:50 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 7 deg. The sun altitude is -58.5 deg. The galactic latitude b = -15 deg., longitude l = 147 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3050758 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 11.63s , +41d 55m 39.9s) | C | 180 | 18.2 | 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 47.32s , +41d 32m 52.8s) | C | 180 | 12.7 | 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/42828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40896] EP251124a: Swift-XRT observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42827 SUBJECT: EP251124a: Swift-XRT observations DATE: 25/11/24 17:36:48 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected source EP251124a, collecting 2.5 ks of Photon Counting (PC) mode data between T0+5.1 ks and T0+11 ks after the trigger. The field is full of extended emission due to a cluster of galaxies. We have detected 3 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J025449.9+413724): ================================== RA (J2000.0): 43.7081 = 02 54 49.94 Dec (J2000.0): +41.6234 = +41 37 24.2 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.0 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.1 +/- -2.1)e-11 erg cm^-2 s^-1 Peak rate: (8.5 [+3.4, -3.0])e-3 ct s^-1 Peak flux: (1.80 [+0.71, -0.63])e-13 erg cm^-2 s^-1 ECF: 2.12e-11 erg cm^-2 ct^-1 assuming NH=2.22e+22 cm^-2, gamma=5.93 determined from a spectral fit. LSXPS UL: 1.0e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `2MASX J02544959+4137278' is 5.1" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 3 (SWIFT J025510.5+413444): ================================== RA (J2000.0): 43.7940 = 02 55 10.56 Dec (J2000.0): +41.5789 = +41 34 44.0 Error: 5.7 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.8 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-1.6 +/- -1.6)e-10 erg cm^-2 s^-1 Peak rate: (3.8 [+2.5, -2.2])e-3 ct s^-1 Peak flux: (6.0 [+4.0, -3.4])e-13 erg cm^-2 s^-1 ECF: 1.57e-10 erg cm^-2 ct^-1 assuming NH=2.84e+21 cm^-2, gamma=0.31 determined from a spectral fit. LSXPS UL: 1.6e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Source 6 (SWIFT J025445.0+413429): ================================== RA (J2000.0): 43.6876 = 02 54 45.02 Dec (J2000.0): +41.5749 = +41 34 29.6 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.0 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0245 [+0.0084, -0.0071] ct s^-1 Mean flux: (8.9 [+3.1, -2.6])e-13 erg cm^-2 s^-1 Peak rate: 0.043 [+0.022, -0.018] ct s^-1 Peak flux: (1.56 [+0.81, -0.66])e-12 erg cm^-2 s^-1 ECF: 3.63e-11 erg cm^-2 ct^-1 assuming NH=1.20e+21 cm^-2, gamma=1.87 determined from a spectral fit. LSXPS UL: 3.2e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. 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/EP/EP_FIELD00083. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40895] GRB 251124b: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42826 SUBJECT: GRB 251124b: Fermi GBM Final Real-time Localization DATE: 25/11/24 17:34:45 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 12:58:03 UT on 24 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251124b (trigger 785681888.46989 / 251124540). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 262.1, Dec = 18.4 (J2000 degrees, equivalent to J2000 17h 28m, 18d 23'), with a statistical uncertainty of 13.1 degrees. The angle from the Fermi LAT boresight is 52.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40894] LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42825 SUBJECT: LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations DATE: 25/11/24 17:22:31 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> J. H. Gillanders (Oxford), A. Aryan, T.-W. Chen, Y.-H. Lee, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. J. Smartt (Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, H.-Y. Hsiao, 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: Here we report follow-up observations of the candidate optical counterpart AT 2025adht (first reported by Franz et al., GCN 42675; see also Anand et al., GCN 42677; Burkhonov et al., GCN 42798) to the LIGO-Virgo-KAGRA (LVK) gravitational-wave event S251112cm (LVK Collaboration, GCN 42650). We observed AT 2025adht utilizing the 1m LOT 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 LOT epoch of observations began at 20:31 UTC on November 21, 2025 (MJD 61000.855), 9.225 days after the GW trigger. The second LOT epoch began at 20:16 UTC, or MJD 61001.845, 10.207 days after the GW 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 DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 images using the 'hotpants' (Becker 2015, ascl.soft. ascl:1504.004) algorithm. Moreover, we further utilized AutoPhOT to perform PSF photometry. The details of the observations and the measured magnitudes (in the AB system) are as follows: Telescope | Filter | MJD (start) | t - t0 (d) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61000.855 | 9.225 | 300 * 6 | 21.83 +/- 0.06 | 1".2 | 1.41 LOT | r | 61001.845 | 10.207 | 300 * 6 | 21.86 +/- 0.08 | 1".2 | 1.46 Burkhonov et al. (GCN 42698) report a (PS1-equivalent) r-band magnitude of 21.64 +/- 0.1 on MJD 60994.009 (2.37 days post-GW trigger). Our observations indicate that AT 2025adht has faded only slightly in the ~week since detection. The slow evolution indicates that AT 2025adht is not some rapidly declining kilonova-like transient; we instead suspect that AT 2025adht is a background supernova near peak, hence the slow evolution. This interpretation is supported by the Legacy Survey's host galaxy phot-z estimate (0.139 +/- 0.033; see also Anand et al., GCN 42677). The presented magnitudes are calibrated using field stars from the ATLAS-RefCat2 catalog from MAST (Tonry et al. 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinction of A_r = 0.06 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology and details on the capabilities of Lulin observatory telescopes can be found in Aryan et al. 2025, ApJS, 281, 20. doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40893] EP251124a: Optical upper limit with Kinder observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42824 SUBJECT: EP251124a: Optical upper limit with Kinder observations DATE: 25/11/24 17:15:34 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> Z. N. Wang (HNAS), A. Aryan, T.-W. Chen, W.-J. Hou, Y.-H. Lee (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, H.-C. Lin, C.-S. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), S. Yang, 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 EP251124a (Zhou et al., GCN 42816) using the 40cm 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). Our SLT observation started at 16:21 UTC on the 24th of November 2025 (MJD 61003.477), 0.27 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 utilised the Python-based package AutoPhOT (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the Pan-STARRS1 3Pi archive image (Chambers et al. 2016, arXiv:1612.05560) using the 'hotpants' (Becker 2015, ascl.soft. ascl:1504.004) algorithm. In the difference image, we do not detect any uncataloged sources within the 20" error circle, for each of the three EP-FXT positions reported. We note that the position of FXTB-2 is not covered by Pan-STARRS1. Although this field is included in SDSS DR14 (Abolfathi et al. 2018, arXiv:1707.09322), we do not find any new or uncataloged sources by eye within the 20″ error circle of FXTB-2. Moreover, we further utilized AutoPhOT to perform the PSF photometry. The details of the observations and the 3-sigma upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61003.477 | 0.27 | 300 * 24 | >21.7 | 1".40 | 1.19 The presented magnitude is calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry et al. 2018, ApJ, 867, 105) and is not corrected for the expected Galactic foreground extinction of A_r = 0.27 mag in the direction of the transient (Schlafly & Finkbeiner 2011). Our observation agrees with Mohan et al. (GCN 42817) and provides a deeper constraint. 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, ApJS, 281, 20. doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40892] GRB 251121B: Fermi GBM Final Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42823 SUBJECT: GRB 251121B: Fermi GBM Final Localization DATE: 25/11/24 16:55:01 GMT FROM: atrigg2(a)lsu.edu The Fermi GBM team reports the detection of a likely SHORT GRB "At 23:44:26.90 UT on 22 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251121B (trigger 785547871/251122989). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 336.52, Dec = -55.63 (J2000 degrees, equivalent to J2000 22h 26m, -55d 38'), with a statistical uncertainty of 10.74 degrees. The angle from the Fermi LAT boresight is 36.00 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40891] EP251118A: 6 GHz VLA Detection
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42822 SUBJECT: EP251118A: 6 GHz VLA Detection DATE: 25/11/24 15:40:05 GMT FROM: muskan.yadav(a)students.uniroma2.eu Muskan Yadav, Roberto Ricci, Eleonora Troja (U Rome) report: We observed the position of EP251118A (Jiang et al., GCN 42749; Malesani et al., GCN 42751) with the Karl G. Jansky Very Large Array (VLA) on 2025 November 20, starting at 13:52 UT (~1.88 days after the EP/WXT trigger), at a central frequency of 6 GHz. In our preliminary analysis, we detect a radio counterpart at 6 GHz with a flux density of ∼74 μJy. The position is consistent with the optical counterpart (An et al., GCN 42756; Belkin et al., GCN 42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773; Lee et al., GCN 42780; Li et al., GCN 42776; Liu et al., GCN 42793; Moskvitin et al., GCN 42785; Aryan et al., GCN 42798; Gupta et al., GCN 42787) and the X-ray counterpart (Shi et al., GCN 42754). We thank the VLA staff for rapidly executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40890] Fermi GRB 251124a: Global MASTER-Net observations report
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42821 SUBJECT: Fermi GRB 251124a: Global MASTER-Net observations report DATE: 25/11/24 15:30:22 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 251124a ( Fermi GBM team, GCN 42820) errorbox 5857 sec after notice time and 5878 sec after trigger time at 2025-11-24 14:36:01 UT, with upper limit up to 13.0 mag. Observations started at twilight. The observations began at zenith distance = 62 deg. The sun altitude is -10.2 deg. The galactic latitude b = 29 deg., longitude l = 38 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3050796 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 5938 | 2025-11-24 14:36:01 | MASTER-Kislovodsk | (17h 11m 31.23s , +16d 54m 33.8s) | P- | 120 | 12.6 | 6078 | 2025-11-24 14:38:21 | MASTER-Kislovodsk | (17h 11m 31.15s , +16d 54m 22.6s) | P- | 120 | 12.5 | 6218 | 2025-11-24 14:40:41 | MASTER-Kislovodsk | (17h 11m 32.20s , +17d 16m 49.8s) | P| | 120 | 12.2 | 6218 | 2025-11-24 14:40:41 | MASTER-Kislovodsk | (17h 11m 31.11s , +16d 54m 13.1s) | P- | 120 | 13.0 | 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/42821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40889] GRB 251124a: Fermi GBM Final Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42820 SUBJECT: GRB 251124a: Fermi GBM Final Localization DATE: 25/11/24 15:09:47 GMT FROM: Andreas von Kienlin at MPE <azk(a)mpe.mpg.de> The Fermi GBM team reports the detection of a LONG GRB "At 12:58:03.47 UT on 24 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251124a (trigger 785681888/251124540). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.14, Dec = 16.86 (J2000 degrees, equivalent to J2000 17h 12m, +16d 51'), with a statistical uncertainty of 1.00 degrees. The angle from the Fermi LAT boresight is 63 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42820. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40888] LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42819 SUBJECT: LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901 DATE: 25/11/24 15:06:20 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, L. P. Xin, Z. H. Yao, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), H. Yang, O. Godet, J.-L. Atteia, M. Brunet, S. Guillot (IRAP), M. Pillas (IAP) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of the high-energy transient SVOM J2320.0-2901 detected by SVOM/ECLAIRs (Yang et al., GCN 42797), right after S251105aj reported by LIGO/Virgo/KAGRA (The LIGO-Virgo-Kagra Collaboration, GCN 42587; GCN 42616). The observation began at 2025-11-16T00:47:45 UT, 10.5 days after SVOM/ECLAIRs detection, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The VT field of view covered 96% of the 90% C.L. ECLAIRs error region, but no uncataloged sources were detected within the error box of ECL. VT also covered three EP/FXT sources (source#1: RA, Dec = 349.8643, -29.0602 deg; source#2: 350.1419, -29.0148 deg; source#3: 349.9737, -28.8522 deg) reported by Guillot et al. (GCN 42818). None of the known sources became apparent brighter within errorbox of three FXT candidates compared with Legacy Survey DR10. The 3 sigma upper limit was VT_R > 23.6 mag and VT_B > 23.8 mag with the exposure time of 65*70 sec. Further analysis is ongoing. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42819. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40887] LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42818 SUBJECT: LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901 DATE: 25/11/24 15:05:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S. Guillot, H. Yang, O. Godet, J.-L. Atteia (IRAP), M. Pillas (IAP), L. P. Xin, Y. N. Ma, H. W. Pan, T. Zhao (NAOC), Y. J. Yi, A. Li (BNU), R. X. Hu (WHU), D. Z. Du (ZJU), C. Y. Wang (THU) on behalf of the Einstein Probe (EP) team: EP-FXT performed a Target of Opportunity observation of the high-energy transient SVOM J2320.0-2901 detected by SVOM/ECLAIRs (Yang et al., GCN 42797), in a search for possible counterparts of the compact binary merger candidate S251105aj (The LIGO-Virgo-Kagra Collaboration, GCN 42587). The observation was conducted at 2025-11-15T21:39:22 UTC with an exposure of 5 ks, about 10.36 days after the GW trigger and the detection time of SVOM J2320.0-2901. EP-FXT covered the full area of the 90% C.L. ECLAIRs error region and detected six sources above a SNR of 4.5 within 15 arcminutes from SVOM J2320.0-2901. Their information is summarized below (RA/Dec in degrees with 10" error radius (90% C.L.); fluxes are the observed ones in 0.5–10 keV): # | Name | RA | Dec | Flux (erg/s/cm^2) | SNR —---------------------------------------------------------------------------------------------------- 1 | EPF_J231927.4-290337 | 349.8643 | -29.0602 | 1.4e-13 | 4.7 2 | EPF_J232034.0-290053 | 350.1419 | -29.0148 | 2.2e-13 | 10.0 3 | EPF_J231953.7-285108 | 349.9737 | -28.8522 | 1.7e-13 | 5.7 4 | EPF_J231906.2-290806 | 349.7760 | -29.1351 | 3.4e-13 | 5.8 5 | EPF_J232051.4-285356 | 350.2140 | -28.8990 | 2.4e-13 | 8.4 6 | EPF_J232108.1-290032 | 350.2839 | -29.0088 | 2.6e-13 | 7.9 We cross-matched all six FXT detections against the SIMBAD, NED, and Vizier catalogues, using a 20″ matching radius (for a galaxy at 2000 Mpc, this corresponds to an offset of ~200 kpc). Five FXT detections (#2,3,4,5,6) are matched to five optical quasars correspondingly, with their redshifts in a range of 0.721 to 1.641, higher than z=0.374 estimated for the GW event. The remaining source (#1) is matched to a source from the KiDSDR4 QSOs photometric redshifts catalog (Nakoneczny et al., 2021), which is classified as a quasar with 68% probability and a photometric redshift of 0.5 +/- 1.2 based on machine learning estimates. We conducted SVOM/VT on this field with the results reported in GCN 42819. Further FXT observations of these candidates will be conducted. 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/42818. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40886] EP251124a: GROWTH-India Telescope optical upper limits
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42817 SUBJECT: EP251124a: GROWTH-India Telescope optical upper limits DATE: 25/11/24 15:02:41 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan (IITB), S. Patil (IITB), D. Eappachen (IIA), V.Swain (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP transient (Zhou et al., GCN 42816), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-11-24T13:25:59 UT, i.e., about 2.27 hours after the EP-WXT trigger. Two exposures were obtained each in r' and g' filters. We did not detect any transient in our images within the WXT localization region and at the position of FXT sources - FXTA, FXTB1, and FXTB2. The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (min) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | ------------- | ------------------- | ---------------- | | 61003.55971 | r' | 135.9 | 300 | 20.5 | | 61003.56539 | g' | 144.1 | 300 | 20.8 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42817. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40885] EP251124a: Einstein Probe detection of an X-ray transient
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42816 SUBJECT: EP251124a: Einstein Probe detection of an X-ray transient DATE: 25/11/24 13:17:56 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Zhou (PMO, CAS), J. -Y. Cao (IHEP), H.-N. Yang, and Z.-X. Ling (NAO, CAS) 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 EP251124a. The transient triggered EP-WXT (ID: 01709248862) at 2025-11-24T11:10:05 (UTC). The WXT position of the source is R.A. = 43.732 deg, DEC = 41.577 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. According to the FXT onboard alert, which provided coordinates calculated autonomously on board the satellite, FXTA detected an X-ray source and FXTB detected two X-ray sources (denoted as FXTB-1 and FXTB-2) within the WXT error circle. Their coordinates (J2000) are: FXTA: R.A. = 43.7117 deg, DEC = 41.5715 deg FXTB-1: R.A. = 43.7188 deg, DEC = 41.5692 deg FXTB-2: R.A. = 43.7061 deg, DEC = 41.6121 deg All FXT localizations are reported with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). FXTB-1 is consistent with the source detected by FXTA. Further information will be updated when the telemetry data is 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/42816. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40884] GRB 251116C: Swift-XRT confirmation of fading
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42815 SUBJECT: GRB 251116C: Swift-XRT confirmation of fading DATE: 25/11/24 10:30:46 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, M. G. Bernardini, B. Sbarufatti, C. Salvaggio, R. Brivio, A. Mei (INAF-OAB) report on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the SVOM/ECLAIRs-detected burst GRB 251116C (Pillas et al., GCN 42703). The observations now extend from T0+10 ks to T0+452 ks and have a total exposure time of 6.1 ks. The previously-reported "Source 1" (Evans et al., GCN 42721), is now found to be fading with ~3-sigma significance, and is therefore likely the GRB afterglow. The results of the XRT-team automatic analysis of the source are available at https://www.swift.ac.uk/SVOM/team/SVOM_FIELD00051/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00051/. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42815. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40883] GRB 251122A/EP251122a: FTW optical and NIR observations
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42814 SUBJECT: GRB 251122A/EP251122a: FTW optical and NIR observations DATE: 25/11/23 22:37:25 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Xander J. Hall (CMU), Brendan O’Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the FXT localization of GRB 251122A/EP251122a (Wang et al., GCN 42779; Lin et al., GCN 42800; Yin et al., GCN 42808; Wang et al., GCN 42809) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands simultaneously for 40 x 180 s starting at 2025-11-23T00:06:12 UT (0.43 days after the trigger). We used r-band templates from the DESI Legacy Survey for difference imaging and did not detect the source identified by Cheng et al. (GCN 42803), Li et al. (GCN 42806), Sun et al. (GCN 42807), Ma et al. (GCN 42811), and Gupta et al. (GCN 42813) at a 3-sigma depth of r > 24 AB mag. The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42814. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40882] GRB 251122A/EP251122A: 1.3m DFOT optical detection
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42813 SUBJECT: GRB 251122A/EP251122A: 1.3m DFOT optical detection DATE: 25/11/23 20:02:06 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Debalina Kar, Pankaj Pawar, Divyanshu Janghel, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of GRB251122A/ EP251122A detected by Einstein Probe (Wang et al. 2025, GCN 42799) and SVOM (Lin et al. 2025, GCN 42800) 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 2025-11-22 at 16:03:25 UT, i.e., ~ 2.15 hours after the EP trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect a faint optical afterglow in our stacked image within the error box of EP/FXT (Wang et al. 2025, GCN 42799, 42809) and SVOM/ECLAIRs (Lin et al. 2025, GCN 42800). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude =============================================================== 2025-11-22 16:03:25 ~2.15 R 300s*19 22.37 +/-0.04 The optical detection of the burst is consistent with WU et al. 2025 (GCN 42801); Lipunov et al. 2025 (GCN 42802); Cheng et al. 2025 (GCN 42803); Saccardi et al. 2025 (GCN 42804); Cotter et al. 2025 (GCN 42805); Li et al. 2025 (GCN 42806); Sun et al. 2025 (GCN 42807); Ma et al. 2025 (GCN 42811) . 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/42813. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40881] The EP-WXT trigger 01709248783 is likely a flaring star
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42812 SUBJECT: The EP-WXT trigger 01709248783 is likely a flaring star DATE: 25/11/23 09:51:43 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> C.-L. Guo (NAO, CAS), J. Yang (ZZU), W.-F. Wen (SZTU), and Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709248783 at the time of 2025-11-23T09:00:39, is likely a stellar flare associated with a Double or Multiple Star BPS CS 31060-0015. The estimated flux of the flare is around 1e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3.8e30 erg/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/42812. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40880] GRB 251122A / EP251122a: Xinglong 2.16m optical observation
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42811 SUBJECT: GRB 251122A / EP251122a: Xinglong 2.16m optical observation DATE: 25/11/23 08:45:24 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, X. H. Han, P. P. Zhang, H. L. Li, Z. H. Yao, J. Zheng, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team: We observed the field of GRB 251122A triggered by SVOM/ECLAIRs (Lin et al., GCN 42800) and EP/WXT (Wang et al., GCN 42799; Yin et al., GCN 42808; Wang et al., GCN 42809) using the 2.16m telescope located at Xinglong observatory, China, equipped with the BFOSC camera. We obtained 7*200s frames in R-band, starting at 14:17:55 UT on 2025-11-22, about 20.8 minutes after the trigger. The optical counterpart (Wu et al., GCN 42801; Lipunov et al., GCN 42802; Cheng et al., GCN 42803; Saccardi et al., GCN 42804; Cotter et al., GCN 42805; Li et al., GCN 42806; Sun et al., GCN 42807) was detected in the stacked image in R band. The magnitude is: mid time (min) | exposure time (s) | band | mag | mag err ---------------|-------------------|------|--------|-------- 32.9 | 7*200 | R | 22.7 | 0.1 The photometry calibration was performed with nearby USNO-B1.0 1040-0024912 as the reference star. Our photometry was 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/42811. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40879] EP251118A: 3.6m DOT optical afterglow detection
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42810 SUBJECT: EP251118A: 3.6m DOT optical afterglow detection DATE: 25/11/23 04:45:13 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Dhruv Jain, Debolina Kar, and Kuntal Misra (ARIES) report: We observed the field of EP251118A detected by Einstein Probe( Jiang et al. 2025, GCN 42749) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-11-22 at 04:57:21.74 UT, i.e., ~84.24 hours after the Einstein Probe trigger. We have taken multiple frames with an exposure time of 120 s in the r filter. We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of NOT (Malesani et al. 2025, GCN 42751). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-22 04:57:21.74 ~ 84.24 r 120s*9 22.33 +/- 0.18 Our detection is consistent with Malesani et al. 2025 (GCN 42751); Belkin et al. 2025 (GCN 42758); Yadav et al. 2025 (GCN 42760); Busmann et al. 2025 (GCN 42763); Francile et al. 2025 (GCN 42767); Rodríguez et al. 2025 (GCN 42773); Li et al. 2025 (GCN 42776); Lee et al. 2025 (GCN 42780); Moskvitin et al. 2025 (GCN 42785); Gupta et al. 2025 (GCN 42787); Liu et al. 2025 (GCN 42793); Aryan et al. 2025 (GCN 42798). 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 Gaia catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42810. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40878] GRB 251122A / EP251122a: EP-FXT counterpart detection
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42809 SUBJECT: GRB 251122A / EP251122a: EP-FXT counterpart detection DATE: 25/11/23 03:57:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.-T. Wang (YNAO), Y.-H. I. Yin (HKU), G. J. Yang (NAOC), H.-Z. Wu (HUST) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 251122A (SVOM/sb25112204, Lin et al., GCN 42800), also triggered by EP/WXT as EP251122a (Wang et al., GCN 42799) at 2025-11-22T17:08:09 (UTC), about 3.2 hours after the SVOM/ECLAIRs trigger, with an exposure time of 1719 s. One uncatalogued source is detected within the ECLAIRs error circle, and the source is spatially consistent with the counterpart reported in optical and X-ray bands, including detections (Cheng et al., GCN 42803; Li et al., GCN 42806; Sun et al., GCN 42807; Yin et al., GCN 42808) and several upper limits (Wu et al., GCN 42801; Lipunov et al., GCN 42802; Saccardi et al., GCN 42804; Cotter et al., GCN 42805). Preliminary analysis on this source are automatically conducted, and details are listed as follows. Source 1: EPF_J023205.2+140740 RA (J2000): 38.0226 Dec (J2000): 14.1282 Flux: 5.27 x 10^-13 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.04 x 10^-13 erg/s/cm2 (1 sigma) The position uncertainty of the source is about 10 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/42809. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40877] EP251122a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 23 Nov '25

23 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42808 SUBJECT: EP251122a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/11/23 03:13:31 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), B.-T. Wang (YNAO), G. J. Yang (NAOC), H.-Z. Wu (HUST) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251122a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 42799) and SVOM/ECLAIRs as GRB 251122A (Lin et al, 42800), and followed by several optical telescopes (Wu et al., GCN 42801, Lipunov et al., GCN 412802, Cheng et al., GCN 42803, Saccardi et al., GCN 42804, Cotter et al., GCN 42805, Li et al., GCN 42806, Sun et al., GCN 42807). The refined analysis of the WXT data shows that the event started at T0=2025-11-22T13:53:43 (UTC) and lasted for 10 s with a single pulse, before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.33 x 10^21 cm^-2 and a photon index of 1.26 (-0.58/+0.59). The derived average unabsorbed 0.5-4 keV flux is 2.07 (-0.67/+0.77) x 10^(-9) erg/s/cm^2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2025-11-22T13:57:19 (UTC), about 4 minutes after T0. The exposure time of this observation is 6029 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 38.0220, 14.1283 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The light curve displays two pulses structure lasting for around 400 s. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 1.33 x 10^21 cm^-2 and a photon index of 1.74 (-0.05/+0.04). The derived average unabsorbed 0.5-10 keV flux is 7.66 (-0.30/+0.33) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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/42808. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40876] LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42797 SUBJECT: LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search DATE: 25/11/22 10:00:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, O. Godet, J.-L. Atteia, M. Brunet, S. Guillot (IRAP), M. Pillas (IAP), L. P. Xin, Y. N. Ma (NAOC) Using the event-by-event data downloaded through the X-band ground stations, we report on the identification of a faint SVOM/ECLAIRs transient SVOM J2320.0-2901 detected at 2025-11-05T13:00:48.34 UTC (T0), 88.4 s after the compact binary merger candidate S251105aj (The LIGO-Virgo-Kagra Collaboration, GCN 42587). This transient was detected through an offline targeted search for possible counterparts of the GW event S251105aj. SVOM J2320.0-2901 was detected with a timescale of 82 s and below 60 keV, with a best signal-to-noise ratio of 6.1 starting at T0. The localization of SVOM J2320.0-2901 is RA, Dec = 349.998, -29.022 degrees: RA (J2000) = 23h20m00s Dec (J2000) = -29d01m19s with a 90% C.L. radius of 13.9 arcmin (including a systematic error of 6 arcmin added in quadrature). This position is about 2 degrees outside the 99% area contour of the Bilby.multiorder.fits skymap of S251105aj. At the time of the GW trigger, ECLAIRs was covering 88% of the skymap 99% area. The time-averaged spectrum from T0 to T0+82 s in the energy range of 5-60 keV is well fitted by a blackbody (BB) model, with a measured temperature of 7.8 (+1.5/-1.2) keV. With this model, the total 4-120 keV flux is (3.6+/-0.8)e-9 erg/cm^2/s. Assuming a distance of 2071 Mpc (z=0.374) for the source, this corresponds to a luminosity of 1.8e48 erg/s and a BB emission radius of 1.9e6 cm. A broken power-law model is also tested, providing a comparable fit, though with less well-constrained parameters of photon index 1 around -0.5, break energy of 22 (+21/-10) keV, and photon index 2 around 2.9. At this stage, the nature of SVOM J2320.0-2901 is unknown. We conducted SVOM/VT and EP/FXT follow-up observations on this field. The results will be published in dedicated circulars. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this source is: Hui Yang (IRAP) (hui.yang(a)irap.omp.eu) View this GCN Circular online at https://gcn.nasa.gov/circulars/42797. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40875] GRB 251122A / EP251122a: WFST optical observations
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42807 SUBJECT: GRB 251122A / EP251122a: WFST optical observations DATE: 25/11/22 17:50:46 GMT FROM: ylhua(a)pmo.ac.cn Tian-Rui Sun, Yan-Long Hua (PMO), Chao Wu (NAOC), Jin-Jun Geng, Xue-Feng Wu, Jun-Jie Wei,, Yi-Fang Liang, Ding-Fang Hu, Guan-Xiao Li, Yuan-Tai Yang, Xu Kong, Ji-An Jiang report on behalf of the WFST team: Following the detection of GRB 251122A / EP251122a by SVOM/ECLAIRs (Lin et al., GCN 42800) and by the Einstein Probe (Wang et al., GCN 42799), we conducted follow-up observations with the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. WFST began i-band imaging at 2025-11-22T15:45:51 UTC, approximately 1.85 hours after the trigger. The afterglow is clearly detected in the i band, with a preliminary magnitude derived from 10 × 150 s exposures: i = 21.89 ± 0.12 (AB) The photometric calibration was performed using nearby stars from the ATLAS-REFCAT2 catalog, in the AB magnitude system. The reported magnitude is not corrected for Galactic extinction. We thank the staff of WFST and the Lenghu observation station for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42807. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40874] GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42806 SUBJECT: GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data DATE: 25/11/22 17:25:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H.L. Li, C. Wu (NAOC), J. T. Palmerio (CEA), L.P. Xin, Y. L. Qiu (NAOC), Z.-Y. Lin, C. Lachaud (APC) report on behalf of the SVOM team. SVOM/VT performed an automatic slew on the burst of GRB 251122A/EP251122a (sb25112204) triggered by SVOM/ECLAIRs (Lin et al., GCN 42800) and EP/WXT(Wang et al., GCN 42799). SVOM/VT began observing the field automatically at 2025-11-22T14:02:17 UTC, ~5.15 minutes after the T0 (SVOM trigger time:2025-11-22T13:57:08), with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. We confirm the detection of the source reported by Cheng et al. (GCN 42803) in the VT_R band of sequence 1 and 3 with the downlinked VHF data. The AB magnitude was derived as follows: -------------------------------------------- (T-T0)mid exptime band mag 7.65 min 300 sec VT_R 21.82 +/-0.12 88.30 min 300 sec VT_R 21.96 +/-0.15 No correction for Galactic extinction was applied to the photometry. This result is consistent with the report by Wu et al.(GCN 42801), Lipunov et al.(GCN 42802), Saccardi et al.(GCN 42804), Cotter et al.(GCN 42805). 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/42806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40873] GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42805 SUBJECT: GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit DATE: 25/11/22 17:04:27 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> L. Cotter, G. Corcoran (UCD), J. A. Chacon (PUC), 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 transient event GRB 251122A / EP251122a detected by EP/WXT (Wang et al., GCN 42799) and by SVOM/ECLAIR (Lin et al., GCN 42800) with the Las Cumbres Observatory (LCO) network. We acquired six 300 s exposures in the r band starting on 2025-11-22 at 15:20:01 UTC (86 min after the EP/EXTtrigger). No new source is detected within the error circle provided by EP/FXT (Wang et al., GCN 42799) and SVOM/MXT (Lin et al., GCN 42800). From the stacked r-band images we obtained a three sigma upper limit of r > 22.4 mag (AB), calibrated against the Pan-STARRS catalog and is not corrected for Galactic extinction. We do not detect the candidate counterpart reported by Cheng et al. (GCN 42803), which was however fainter than our limit and observed at an earlier epoch. Our non-detection is also consistent with previous reports (Wu et al., GCN 42801; Lipunov et al., GCN 42802; Saccardi et al., GCN 42804). View this GCN Circular online at https://gcn.nasa.gov/circulars/42805. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40872] GRB 251122A / EP251122a: LCO optical upper limits
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42804 SUBJECT: GRB 251122A / EP251122a: LCO optical upper limits DATE: 25/11/22 16:36:43 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), L. P. Xin (NAOC), D. Turpin, J. T. Palmerio (CEA/Irfu), C. Wu (NAOC), B. Cordier (CEA/Irfu), Z.-Y. Lin, C. Lachaud (APC), report on behalf of the SVOM mission team: We observed the field of GRB 251122A / EP251122a detected by SVOM/ECLAIRs (Lin et al. GCN 42800) and EP/WXT (Wang et al., GCN 42799) with the LCO 1m telescope at the Siding Spring Observatory equipped with the Sinistro instrument. Our observation started at 2025-11-22T14:56:27 (UTC) about 1 hour after the trigger. We obtained 3x200 s exposures in each of the SDSS r and Pan-STARRS z filters. The r-band images are unfortunately trailed, which reduces our sensitivity. In the stacked images, we do not detect any new optical source within the EP/FXT and SVOM/MXT error circles. We measure the following 3-sigma upper limits calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r > 20.8 AB (mid time 80 min after the SVOM T0); z > 20.4 AB (mid time 63 min after the SVOM T0). Our results are consistent with the limits reported by Wu et al. (GCN 42801). We do not detect the candidate counterpart reported by Cheng et al. (GCN 42803), which is fainter and reported at an earlier epoch than our observations. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/42804. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40871] EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42803 SUBJECT: EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations DATE: 25/11/22 16:25:24 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> Y.-C. Cheng (NCU), J.Y.B Choo (UKM), A.N. Garcia (PUP), A.L.A.M. Nasir (UniSZA), J.-L. Yang (NCU) on behalf of the 47th International School for Young Astronomers (ISYA) in Taipei, A. Aryan, T.-W. Chen, Y.-H. Lee, C.-S. Lin (all NCU), S. Yang (HNAS), A. K. H. Kong (NTHU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), 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 EP251122a (Wang et al., GCN 42799) using the 1m LOT 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). A follow-up observation by SVOM found a temporally and spatially coincident long GRB 251122A (Lin et al. GCN 42800). The first LOT epoch of observations began at 14:13 UTC on the 22nd of November 2025 (MJD 61001.592), 0.31 hr after the EP-WXT trigger. We used the Kinder pipeline (Yang et al. A&A 646, A22) to stack the images and perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image. In the difference image, we find a faint, uncataloged optical counterpart candidate at RA, DEC = 02:32:05.1284, +14:07:43.826; lying within the 20" EP-FXT localization circle. The counterpart candidate is likely associated with the DESI Legacy Survey (DR10) galaxy at RA, Dec = 38.0213, 14.1289, with r = 24.64 mag and a photometric redshift of 1.113 ± 0.368. We perform PSF photometry on the position of the source with the stacked frames. The details of the observations and measured PSF magnitude (in the AB system) of the proposed counterpart of EP251122a are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61001.592 | 0.31 | 300 * 6 | 23.1 +/- 0.2 | 0".93 | 1.01 We caution that the optical counterpart candidate is detected at a level close to the detection limit (>23.2 mag). Our observation is consistent with Wu et al. (GCN 42801) and deeper than their limits. The presented magnitude is calibrated using the field stars from the Pan-STARRS1 DR2 and is not corrected for the expected Galactic foreground extinction of A_r = 0.35 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, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42803. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40870] EP251122a: Global MASTER-Net observations report
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42802 SUBJECT: EP251122a: Global MASTER-Net observations report DATE: 25/11/22 16:09:30 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 EP251122a ( EP Team et al., GCN 42799) errorbox 3880 sec after notice time and 5537 sec after trigger time at 2025-11-22 15:26:08 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 60 deg. The sun altitude is -18.9 deg. The galactic latitude b = -42 deg., longitude l = 157 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3049413 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 5627 | 2025-11-22 15:26:08 | MASTER-Kislovodsk | (02h 30m 23.79s , +14d 20m 55.2s) | C | 180 | 16.9 | 5628 | 2025-11-22 15:26:08 | MASTER-Kislovodsk | (02h 30m 33.71s , +13d 58m 00.6s) | C | 180 | 17.8 | 7537 | 2025-11-22 15:57:58 | MASTER-Kislovodsk | (02h 30m 49.90s , +14d 17m 52.7s) | C | 180 | 18.7 | 7539 | 2025-11-22 15:58:00 | MASTER-Kislovodsk | (02h 31m 02.20s , +13d 55m 05.3s) | C | 180 | 19.3 | 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/42802. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40869] GRB 251122A/EP251122a: SVOM/C-GFT upper limit
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42801 SUBJECT: GRB 251122A/EP251122a: SVOM/C-GFT upper limit DATE: 25/11/22 16:06:03 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chao WU (NAOC), Zhe Kang (CHO), 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), Z.-Y. Lin, C. Lachaud (APC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 251122A detected by EP/WXT(Wang et al., GCN 42799, ID:01709248658) and SVOM/ECLAIRs (Lin et al., GCN 42800, SVOM burst-id sb25112204) with LATIOS on SVOM/C-GFT. Observations started at 2025-11-22T13:59:06 UTC, ~118 seconds after the trigger. A series of g, r, and i band images were obtained. No credible candidate was detected within the error box provided by EP/FXT (Wang et al., GCN 42799) and SVOM/MXT (Lin et al., GCN 42800 ) in our images after preliminary processing, the three sigma upper limit is: | Date-Obs (mid-time) | Mid_t - T0 (s) | Exposure Time (s) | Band | Upper Limit (AB) | |---------------------|----------------|-------------------|------|------------------| | 2025-11-22T13:59:45 | 157 | 6×10 | i | 20.05 | The photometry was calibrated against nearby UCAC4 catalogue and no correction for Galactic dust extinction was applied. We thank the observation assistants Bowen Li and Hongyan Xue 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/42801. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40868] GRB 251122A / EP251122a: SVOM detection of a long burst
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42800 SUBJECT: GRB 251122A / EP251122a: SVOM detection of a long burst DATE: 25/11/22 14:26:21 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z.-Y. Lin, C. Lachaud (APC), S. Schanne, D. Turpin (CEA/Irfu), T. Maiolino (LUPM), D. Götz (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the SVOM team: At 2025-11-22T13:57:08 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251122A (SVOM burst-id sb25112204), also triggered by EP/WXT as EP251122a (Wang et al., GCN 42799). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 6 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.68 in the [5-20] keV energy band over a time window of 327.68 seconds starting at 2025-11-22T13:52:01. The localization of the best alert is R.A., Dec. 38.1450, 14.0645 degrees (J2000) with a 90% confidence level (C.L.) radius of 7.48 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-11-22T14:00:05 UTC, 177 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 38.026, +14.124 degrees: R.A. (J2000) = 02h32m06s Dec. (J2000) = +14d07m26s with a 90% C.L. radius of 75 arcseconds. This location is 7.8 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Zheyu Lin: zheyu.lin(a)apc.in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42800. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40867] EP251122a: Einstein Probe detection of an X-ray transient
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42799 SUBJECT: EP251122a: Einstein Probe detection of an X-ray transient DATE: 25/11/22 14:20:22 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.-T. Wang (YNAO), Y.-H. I. Yin (HKU), G. J. Yang (NAOC), H.-Z. Wu (HUST) and W. D. Zhang (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 EP251122a. The transient triggered EP-WXT (ID: 01709248658) at 2025-11-22T13:53:51 (UTC). The WXT position of the source is R.A. = 38.017 deg, DEC = 14.132 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 38.0199 deg, DEC = 14.1277 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is 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/42799. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40866] EP251118a: Continued Optical Detection with Kinder observations
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42798 SUBJECT: EP251118a: Continued Optical Detection with Kinder observations DATE: 25/11/22 13:04:05 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, T.-W. Chen, Y.-H. Lee, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, H.-Y. Hsiao, 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: Followed by our previous detection (Lee et al., GCN 42780 ), we continued to observe the field of the fast X-ray transient EP251118a (Jiang et al., GCN 42749) using the 1m LOT 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 LOT epoch of observations began at 18:09 UTC on November 21, 2025 (MJD 61000.756), 73.45 hours 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 DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'hotpants' (Becker A., 2015, ascl.soft. ascl:1504.004) algorithm. In the difference image, we onece again clearly detected the optical counterpart candidate proposed by Malesani et al. (GCN 42751) at a spectroscopic redshift of z = 1.216 (An et al., GCN 42756), and confirmed by Belkin et al. (GCN 42758); Yadav et al. (GCN 42760); Busmann et al. (GCN 42763); Francile et al. (GCN 42767); Urquijo-Rodríguez et al. (GCN 42773); Moskvitin et al. (GCN 42785); Gupta et al. (GCN 42787); and Liu et al (GCN 42793) Moreover, we further utilized AutoPhOT to perform the PSF photometry. The details of the observations and the measured magnitude(in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61000.756 | 73.45 | 300 * 6 | 22.5 +/- 0.1 | 0".92 | 1.12 The presented magnitude is calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and is not corrected for the expected Galactic foreground extinction of A_r = 0.09 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, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42798. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40865] LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient through targeted search
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42797 SUBJECT: LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient through targeted search DATE: 25/11/22 10:00:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, O. Godet, J.-L. Atteia, M. Brunet, S. Guillot (IRAP), M. Pillas (IAP), L. P. Xin, Y. N. Ma (NAOC) Using the event-by-event data downloaded through the X-band ground stations, we report on the identification of a faint SVOM/ECLAIRs transient detected at 2025-11-05T13:00:48.34 UTC (T0), 88.4 s after the compact binary merger candidate S251105aj (The LIGO-Virgo-Kagra Collaboration, GCN 42587). This transient was detected through an offline targeted search for possible counterparts of the GW event S251105aj. The ECLAIRs source was detected with a timescale of 82 s and below 60 keV, with a best signal-to-noise ratio of 6.1 starting at T0. The localization of the source is RA, Dec = 349.998, -29.022 degrees: RA (J2000) = 23h20m00s Dec (J2000) = -29d01m19s with a 90% C.L. radius of 13.9 arcmin (including a systematic error of 6 arcmin added in quadrature). This position is about 2 degrees outside the 99% area contour of the Bilby.multiorder.fits skymap of S251105aj. At the time of the GW trigger, ECLAIRs was covering 88% of the skymap 99% area. The time-averaged spectrum from T0 to T0+82 s in the energy range of 5-60 keV is well fitted by a blackbody (BB) model, with a measured temperature of 7.8 (+1.5/-1.2) keV. With this model, the total 4-120 keV flux is (3.6+/-0.8)e-9 erg/cm^2/s. Assuming a distance of 2071 Mpc (z=0.374) for the source, this corresponds to a luminosity of 1.8e48 erg/s and a BB emission radius of 1.9e6 cm. A broken power-law model is also tested, providing a comparable fit, though with less well-constrained parameters of photon index 1 around -0.5, break energy of 22 (+21/-10) keV, and photon index 2 around 2.9. At this stage, the nature of this transient is unknown. We conducted SVOM/VT and EP/FXT follow-up observations on this field. The results will be published in dedicated circulars. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this source is: Hui Yang (IRAP) (hui.yang(a)irap.omp.eu) View this GCN Circular online at https://gcn.nasa.gov/circulars/42797. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40864] LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42796 SUBJECT: LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates DATE: 25/11/22 07:28:12 GMT FROM: Hemanth kumar <hemanth.bommireddy195(a)gmail.com> Hemanth Bommireddy (U de Chile), Regis Cartier (UA), Felipe Olivares (U Hawaii), reporting on behalf of the Dark Energy Survey Gravitational Wave (DESGW) spectroscopy team: We report spectroscopic observations of the transients AT2025adgp, AT2025adhf, and AT2025adhs obtained with the SOAR telescope on 2025-11-14 at 04:10:05 UTC (PI: Bommireddy). For each source, we obtained an exposure of approximately 900s. The spectra were preliminarily reduced and classified using the NGSF spectral classification software (Goldwasser et al. 2022). Based on the reported redshifts (GCN 42675), the top 3 template fits for each event are listed below. | event | SN type/event/instrument (χ²/dof) | | -----------| --------------------------------------------------------------------------- | | AT2025adgp | II/2013fs/KAST (~0.83), Ic-BL/1998bw/DFOSC (~0.82), IIn/2010jl/KAST (~0.82) | AT2025adhf | Ic-BL/1998bw/DFOSC (~1.96), Ic-BL/1998bw/EFOSC2-3.6 (~1.99), Ic-BL/1998bw/DFOSC (~2.06)| | AT2025adhs | SLSN-I/PTF10aagc/LRIS (~1.57), Ia-pec/2000cx/KAST (~1.61), SLSN-I/PTF12dam/DBSP (~1.62)| We thank the SOAR staff for their support during these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42796. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40863] GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42795 SUBJECT: GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst DATE: 25/11/22 03:08:50 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> Jimmy DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251121A onboard (T0: 2025-11-21T16:30:58.99 UTC, Fermi Trig 785435463, Glowbug GCN 42794) 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 10.7 in a 0.128 s analysis time bin, starting at T0 - 0.032 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 12,627 deg2 and the 50% credible area is 4,629 deg2 The integrated probability inside the coded field of view is 2%. The NITRATES skymap is consistent with the Ferm/GBM localization reported in the final position notice (GCN 42790). The combined Fermi/GBM+NITRATES 90% credible area is 893 deg2 and the 50% credible area is 256 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=785435495/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/785435495/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/785435495/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=785435495 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/42795. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40862] GRB 251121A: Glowbug gamma-ray detection of a likely short burst
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42794 SUBJECT: GRB 251121A: Glowbug gamma-ray detection of a likely short burst DATE: 25/11/22 02:28:23 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> R. Woolf, C.C. Cheung, 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 251121A, which was also detected by Fermi/GBM (GCN 42790). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-21 16:30:57.936 with a duration of 0.06 s and a total significance of about 9.4 sigma. The light curve comprises a single peak. 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 telescopes 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/42794. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40861] EP251118a: Xinglong-2.16m optical observation
by GCN Circulars 22 Nov '25

22 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42793 SUBJECT: EP251118a: Xinglong-2.16m optical observation DATE: 25/11/22 01:34:51 GMT FROM: liuxing(a)nao.cas.cn X. Liu, J.J. Jin, J. Zheng, Z. Fan, D. Xu, L.B. He, J. An, S.Q. Jiang, Z.P. Zhu, J.J. Jia(NAOC), S.Y. Fu(HUST) report on behalf of a large collaboration: We observed the field of EP251118a detected by EP/WXT (Jiang et al., GCN 42749; Shi et al., GCN 42754;) and likely GRB 251118C (Frederiks et al., GCN 42765; Wang et al., GCN 42766; Delaunay et al., GCN 42770; Woolf et al, GCN 42771) using the Xinglong-2.16m telescope equipped with the BFOSC camera. Observations started at 19:28:32 UT on 2025-11-21 (i.e., 74.77 h after the EP trigger), and 15x300 s R-band frames have been obtained. The optical afterglow (Melasani et al., GCN 42751; An et al., GCN 42756; Belkin et al., GCN42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Rodríguez et al., GCN 42773; Li et al., GCN 42776; Lee et al., GCN 42780; Moskvitin et al., GCN 42785; Gupta et al., GCN42787) was cleary detected in our stacked frame with a magnitude of R = 22.1 +/- 0.1 at a mid-time of 75.28hr, calibrated with Pan-STARRS1 DR2 catalog converted using Lupton (2005) equations 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/42793. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40860] GRB 251115A: Fermi GBM Observation
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42792 SUBJECT: GRB 251115A: Fermi GBM Observation DATE: 25/11/21 23:37:57 GMT FROM: Angus Jameson <abj0023(a)uah.edu> A. Jameson (UAH), S. Bala (USRA), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 03:20:02.67 UT on 15 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251115A (trigger 784869607/251115139), which was also detected by Fermi-LAT (E. Bissaldi et al. 2025, GCN 42696). The Fermi GBM on-ground location is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 80 degrees. The GBM light curve consists of a double-peaked emission with a duration (T90) of about 13 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+13.8 s is best fit by a Band function with Epeak = 36 +/- 6 keV, alpha = -0.7 +/- 0.4, and beta = -2.09 +/- 0.07. The event fluence (10-1000 keV) in this time interval is (3.5 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.064 s in the 10-1000 keV band is 9.0 +/- 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/42792. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40859] The EP-WXT trigger 01709248635 is likely a flaring star
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42791 SUBJECT: The EP-WXT trigger 01709248635 is likely a flaring star DATE: 25/11/21 16:45:02 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), B.-T. Wang (YNAO), H.-Z. Wu (HUST) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709248635 at the time of 2025-11-21T16:11:59, is likely a stellar flare associated with a T Tauri Star HD 285751. The estimated flux of the flare is around 1.0e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.3e32 erg/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/42791. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40858] GRB 251121A: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42790 SUBJECT: GRB 251121A: Fermi GBM Final Real-time Localization DATE: 25/11/21 16:41:36 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 16:30:58 UT on 21 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251121A (trigger 785435463.990588 / 251121688). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 250.6, Dec = -19.8 (J2000 degrees, equivalent to J2000 16h 42m, -19d 48'), with a statistical uncertainty of 19.5 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/bn251121688/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251121688/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251121688/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42790. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40857] Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42789 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB DATE: 25/11/21 14:57:14 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 785388351 / 251121143 at 03:25:46.72 UT on 21 November 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to particle activity." View this GCN Circular online at https://gcn.nasa.gov/circulars/42789. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40856] Fermi trigger No 785388351: Global MASTER-Net observations report
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42788 SUBJECT: Fermi trigger No 785388351: Global MASTER-Net observations report DATE: 25/11/21 14:45:55 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB251121.14 (trigger No 785388351,21h 39m 12.00s , +42d 06m 36.0s, R=11.36) errorbox 39901 sec after notice time and 39938 sec after trigger time at 2025-11-21 14:31:24 UT, with upper limit up to 16.5 mag. Observations started at twilight. The observations began at zenith distance = 2 deg. The sun altitude is -9.1 deg. The galactic latitude b = -8 deg., longitude l = 90 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3048278 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 39968 | 2025-11-21 14:31:24 | MASTER-Kislovodsk | (21h 28m 33.86s , +41d 27m 00.7s) | C | 60 | 15.6 | 39968 | 2025-11-21 14:31:24 | MASTER-Kislovodsk | (21h 34m 49.78s , +41d 04m 07.6s) | C | 60 | 14.0 | 40048 | 2025-11-21 14:32:44 | MASTER-Kislovodsk | (21h 47m 06.83s , +43d 20m 11.1s) | C | 60 | 16.0 | 40048 | 2025-11-21 14:32:44 | MASTER-Kislovodsk | (21h 53m 30.83s , +42d 57m 01.9s) | C | 60 | 13.4 | 40227 | 2025-11-21 14:35:43 | MASTER-Kislovodsk | (21h 49m 03.50s , +41d 25m 22.5s) | C | 60 | 16.1 | 40227 | 2025-11-21 14:35:44 | MASTER-Kislovodsk | (21h 55m 10.89s , +41d 02m 46.0s) | C | 60 | 14.1 | 40308 | 2025-11-21 14:37:04 | MASTER-Kislovodsk | (21h 32m 22.61s , +39d 32m 55.4s) | C | 60 | 16.1 | 40308 | 2025-11-21 14:37:04 | MASTER-Kislovodsk | (21h 38m 18.31s , +39d 09m 16.6s) | C | 60 | 13.7 | 40388 | 2025-11-21 14:38:24 | MASTER-Kislovodsk | (21h 52m 03.41s , +39d 31m 14.7s) | C | 60 | 16.5 | 40388 | 2025-11-21 14:38:24 | MASTER-Kislovodsk | (21h 58m 00.63s , +39d 07m 52.4s) | C | 60 | 14.0 | 40474 | 2025-11-21 14:39:50 | MASTER-Kislovodsk | (21h 30m 34.79s , +41d 17m 12.7s) | C | 60 | 16.2 | 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/42788. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40855] EP251118A: 1.3m DFOT optical afterglow detection
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42787 SUBJECT: EP251118A: 1.3m DFOT optical afterglow detection DATE: 25/11/21 12:03:39 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debolina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251118A detected by the Einstein Probe (Jiang et al. 2025, GCN 42749) 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 2025-11-20 at 20:16:13 UT, i.e., ~ 2.14 days after the Einstein Probe trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of NOT (Malesani et al. 2025, GCN 42751). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ====================================================================== 2025-11-20 20:16:13 ~2.14 R 250s*18 21.15 +/- 0.25 Our detection is consistent with Malesani et al. 2025 (GCN 42751); Belkin et al. 2025 (GCN 42758);Yadav et al. 2025 (GCN 42760); Busmann et al. 2025 (GCN 42763); Francile et al. 2025 (GCN 42767); Rodríguez et al. 2025 (GCN 42773); Li et al. 2025 (GCN 42776); Lee et al. 2025 (GCN 42780); Moskvitin et al. 2025 (GCN 42785). 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 Gaia catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42787. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40854] GRB 251118A: Swift/UVOT Detection
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42786 SUBJECT: GRB 251118A: Swift/UVOT Detection DATE: 25/11/20 22:23:37 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251118A 31.3 ks after the Fermi trigger (GCN Circ. 42743). A fading source consistent with the XRT position (Osbourne et al., GCN Circ. 42782) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 10:14:01.01 = 160.00422 (deg.) Dec (J2000) = -34:31:21.1 = -34.52254 (deg.) with an estimated uncertainty of 0.42 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 31521 52651 885 18.79+/-0.05 white 108251 159027 1113 20.11+/-0.10 v 31678 42929 845 18.60+/-0.19 v 108564 147691 662 >19.73 u 31363 52627 2489 18.41+/-0.05 u 107942 158555 1113 19.61+/-0.15 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.057 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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