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[vsnet-grb-info 41052] SVOM GRB251203.77: Global MASTER-Net observations report
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42975 SUBJECT: SVOM GRB251203.77: Global MASTER-Net observations report DATE: 25/12/03 18:56:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SVOM GRB251203.77 (trigger No 1764786825,03h 27m 07.30s , -07d 18m 36.0s, R=0.1142) errorbox 874 sec after notice time and 959 sec after trigger time at 2025-12-03 18:49:45 UT, with upper limit up to 13.4 mag. The observations began at zenith distance = 52 deg. The sun altitude is -55.8 deg. The galactic latitude b = -48 deg., longitude l = 192 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3059703 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 990 | 2025-12-03 18:49:45 | MASTER-Kislovodsk | (03h 24m 59.88s , -06d 56m 52.1s) | C | 60 | 13.4 | 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/42975. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41051] SVOM GRB251203.76: Global MASTER-Net observations report
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42974 SUBJECT: SVOM GRB251203.76: Global MASTER-Net observations report DATE: 25/12/03 18:56:30 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 SVOM GRB251203.76 (trigger No 1764785366,01h 13m 50.30s , -00d 00m 00.4s, R=0.1345) errorbox 927 sec after notice time and 1072 sec after trigger time at 2025-12-03 18:27:18 UT, with upper limit up to 14.1 mag. The observations began at zenith distance = 44 deg. The sun altitude is -52.1 deg. The galactic latitude b = -62 deg., longitude l = 136 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3059683 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1103 | 2025-12-03 18:27:18 | MASTER-Kislovodsk | (01h 13m 06.79s , +00d 09m 15.4s) | C | 60 | 14.1 | 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/42974. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41050] GRB 251203B: SVOM detection of a burst
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42973 SUBJECT: GRB 251203B: SVOM detection of a burst DATE: 25/12/03 18:54:01 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, N. A. Webb (IRAP), N. Dagoneau, M. Moita (CEA), report on behalf of the SVOM mission team At 2025-12-03T18:10:27 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251203B (SVOM burst-id sb25120304). 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 9 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.85 in the [5-20] keV energy band over a time window of 81.92 seconds starting at 2025-12-03T18:09:25. The localization of the best alert is R.A., Dec. 18.4596, -0.0001 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.07 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-12-03T18:18:55 UTC, 509 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 18.3720, 0.0157 degrees: R.A. (J2000) = 01h13m29.27s Dec. (J2000) = 00d00m56.42s with a 90% C.L. radius of 35.36 arcseconds. This location is 5.34 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. We note the presence of an X-ray source (2E 0110.9-0014) located 20.06 arcsec away from the MXT position. 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 Marius Brunet: mbrunet(a)irap.omp.eu. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42973. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41049] GRB 251129A / EP251129a: SVOM/VT optical color bluer
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42972 SUBJECT: GRB 251129A / EP251129a: SVOM/VT optical color bluer DATE: 25/12/03 15:51:33 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations for GRB 251129A / EP251129a triggered by SVOM/ECLAIRs (sb25112901, Tan et al., GCN 42877, GCN 42879) and Einstein Probe (Wu et al., GCN 42884). The observations showed the color of the afterglow (Evans, GCN 42888; Angulo et al., GCN 42880; Watson, GCN 42883; Wu et al., GCN 42882; Masi, GCN 42885; Li et al., GCN 42887; Page et al., GCN 42891; Lipunov et al., GCN 42892; Moskvitin et al., GCN 42897; Guziy et al., GCN 42899; Sanchez-Ramirez et al., GCN 42900; Jiang et al., GCN 42902; Yaqup et al., GCN 42942; Kuin et al., GCN 42959) was changed from VT_B-VT_R~0.30+/-0.03 mag at 0.5 hours to VT_B-VT_R~0+/-0.05 mag at around 4 to 50 hours post burst. The latest measurements are 21.8+/-0.1 mag in both channels at the mid time of 49.83 hours post burst with the exposure time of 47*70 sec. Our photometry was in AB magnitude and not corrected for Galactic extinction. More follow-up observations are encouraged. 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/42972. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41048] GRB 251201B: Insight-HXMT/HE detection
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42971 SUBJECT: GRB 251201B: Insight-HXMT/HE detection DATE: 25/12/03 14:29:33 GMT FROM: Yue Wang <m18509381757(a)163.com> Yue Wang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-01T16:26:24.000 (T0), Insight-HXMT/HE detected a long-duration GRB 251201B, which is also detected by Fermi/GBM (Fermi GBM team, GCN #42923) and GECAM-B (Yue Wang et. al., GCN #42952). The Insight-HXMT/HE light curve mainly consists of a long pulse with a T90 of 42 +11/-8 s. The 1s peak rate, measured from T0+6.5 s, is 494 cnts/sec. Insight-HXMT/HE detected a total of 8654 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251201B.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org View this GCN Circular online at https://gcn.nasa.gov/circulars/42971. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41047] EP251202a / GRB 251202A: Insight-HXMT/HE detection
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42970 SUBJECT: EP251202a / GRB 251202A: Insight-HXMT/HE detection DATE: 25/12/03 13:45:08 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-02T01:50:52.000 (T0), Insight-HXMT/HE detected a long GRB EP251202a / GRB 251202A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42933 and #42957), Einstein Probe (Einstein Probe (EP) team, GCN #42934, #42937 and #42946) and GOTO (GOTO collaboration, GCN #42947). The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 25 +12/-11 s. The 1s peak rate, measured from T0+8.5 s, is 254 cnts/sec. Insight-HXMT/HE detected a total of 2752 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251202A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org View this GCN Circular online at https://gcn.nasa.gov/circulars/42970. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41046] EP251130a: MAO/AZT-22 optical observations
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42969 SUBJECT: EP251130a: MAO/AZT-22 optical observations DATE: 25/12/03 12:42:19 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> B.Abidkhanov, Y. Rajabov, O. Burkhonov, S. Ehgamberdiev, Y. Tillayev (UBAI), T. Boyqobilov, A. Shaymanov (Maidanak Observatory/UBAI) report on behalf of UBAI team. We observed the field of EP transient EP251130a (Wu et al., GCN 42903 Zhang et al., GCN 42915), also detected by Swift/XRT (Evans et al., GCN 42908), with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2025-12-01 at 20:31:41 UT. In total we obtained 6x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914; Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al., GCN 42918; Moskvitin and Spiridonova, GCN 42919; Aryan et al., GCN 42921; Volnova et al., GCN 42922; Ma et al., GCN 42940; Corcoran et al., GCN 42951; and Rodríguez et. al., GCN 42963) is detected in the stacked frame. Preliminary photometry is the following: Date UTstart Exptime t-T0 Filter OT Err. UL Site/Telescope (nxs) (mid, days) 2025-12-01 20:47:55 6x300 1.40284 R 21.25 0.07 22.59 MAO/AZT-22 van Dalen et al. (GCN Circ. 42918) have reported a redshift of z = 4.035 using GTC OSIRIS+. 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/42969. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41045] GRB 251203A: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42968 SUBJECT: GRB 251203A: Fermi GBM Final Real-time Localization DATE: 25/12/03 11:49:53 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely LONG GRB "At 08:18:45.15 UT on 03 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251203A (trigger 786442730/251203346). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 165.6, Dec = -46.9 (J2000 degrees, equivalent to J2000 11h 02m, 46d 54'), with a statistical uncertainty of 2.2 degrees. The angle from the Fermi LAT boresight is 58 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42968. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41044] GRB 251203A: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42968 SUBJECT: GRB 251203A: Fermi GBM Final Real-time Localization DATE: 25/12/03 11:49:53 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely LONG GRB "At 08:18:45.15 UT on 03 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251203A (trigger 786442730/251203346). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 165.6, Dec = -46.9 (J2000 degrees, equivalent to J2000 11h 02m, 46d 54'), with a statistical uncertainty of 2.2 degrees. The angle from the Fermi LAT boresight is 58 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251203346/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42968. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41043] EP251202a / GRB251202A: AstroSat CZTI detection
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42967 SUBJECT: EP251202a / GRB251202A: AstroSat CZTI detection DATE: 25/12/03 10:02:30 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), U. Pathak (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251202A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 42933) and is associated with EP251202a detected by Einstein Probe (Zhang et. al., GCN Circ. 42937). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-02 01:51:01.50 UTC. The measured peak count rate associated with the burst is 118 (+37, -21) counts/s above the background in the combined data of all quadrants, with a total of 689 (+148, -156) counts. The local mean background count rate was 341 (+4, -5) counts/s. Using cumulative rates, we measure a T90 of 9.4 (+0.5, -1.3) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42967. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41042] GRB 251202A / EP251202a: SVOM/VT optical observation
by GCN Circulars 03 Dec '25

03 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42966 SUBJECT: GRB 251202A / EP251202a: SVOM/VT optical observation DATE: 25/12/03 05:27:52 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Y. L. Qiu, C. Wu, H. L. Li, L. P. Xin, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), J. X. Cao, X. Tian (GXU), Y. Wang (PMO) report on behalf of the SVOM/VT team. SVOM/VT performed Target of Opportunity observations of GRB 251202A / EP251202a triggered by Fermi/GBM (Fermi GBM team, GCN 42933; Bala et al., GCN 42957) and EP/WXT (Zhang et al., GCN 42937; Liang et al., GCN 42946). The observation began at 2025-12-02T06:43:31 UTC, 4.905 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Li et al., GCN 42934; Zhu et al., GCN 42939; O’Neill et al., GCN 42947; Quirola-Vasquez et al., GCN 42948; Kuin & Moss, GCN 42956; Zheng et al., GCN 42964) was clearly detected within EP/FXT and Swift/XRT's errorbox (Zhang et al., GCN 42937; Sbarufatti et al., GCN 42943) in both VT_B and VT_R bands. The measurements in AB magnitude are as below: mid time (h) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 5.307 | 22*50 | VT_B | 19.29 | 0.03 5.300 | 24*50 | VT_R | 18.86 | 0.03 16.816 | 24*50 | VT_B | 20.40 | 0.06 16.726 | 22*50 | VT_R | 19.75 | 0.04 Our photometry was not corrected for Galactic extinction. In the VT_R stacked images, we can clearly see an extended source (g=24.37, r=22.77, z=21.99) at the position 3 arcseconds away from the optical counterpart, compared to Legacy Survey DR10 catalogue, as mentioned by Li et al. (GCN 42934). 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/42966. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41041] GRB 251201B: Fermi GBM Observation
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42965 SUBJECT: GRB 251201B: Fermi GBM Observation DATE: 25/12/02 20:57:29 GMT FROM: Eva Palafox at INAOE <eva.palafox(a)gmail.com> Eva Palafox (INAOE) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:26:24.22 UT on 01 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251201B (trigger 786299189/251201685), which was also detected by Swift BAT (M. J. Moss et al. 2025, GCN 42924), and Swift XRT (J.P. Osborne et al. 2025, GCN 42927). The Fermi GBM on-ground location (GCN 42923) is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 119 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 91 s (50-300 keV). The time-averaged spectrum from T0-22.5 to T0+105.5 s is best fit by a simple power law function with index -1.83 +/- 0.04. A power law function with an exponential high-energy cutoff fits equally well with power law index = -1.71 +/- 0.08 and Epeak = 269.8 +/- 166.0. The event fluence (10-1000 keV) in this time interval is (1.2 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.7 s in the 10-1000 keV band is 4 +/- 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/42965. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41040] EP251202a/GRB 251202A: KAIT optical observations
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42964 SUBJECT: EP251202a/GRB 251202A: KAIT optical observations DATE: 25/12/02 20:38:22 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP251202a/GRB 251202A (Zhang et al., GCN 42937; Liang et al., GCN 42946; Fermi GBM team, GCN 42933; Bala et al., GCN 42957) from 6.29 to 10.59 hours after the burst. A set of 60s clear (roughly R) filter images were obtained. We clearly detected the optical afterglow (Li et al., GCN 42934; Zhu et al., GCN 42939; O’Neill et al., GCN 42947; Quirola-Vasquez et al., GCN 42948; Kuin et al., GCN 42956) in our coadd images. We measure its brightness decayed from 18.7 +/- 0.1 mag (Vega; mid time 6.30 hours) to 19.3 +/- 0.2 mag (mid time of 10.55 hours) with a power-law decay index of 1.07. View this GCN Circular online at https://gcn.nasa.gov/circulars/42964. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41039] EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42963 SUBJECT: EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory DATE: 25/12/02 19:57:57 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> T. Tundidor Rodríguez, 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. Pulido-Torres, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, E. Urquijo-Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). We report on observations of the optical counterpart of the X-ray transient EP251130a, detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wu et al., GCN Circ. 42903) and with detections of Swift-XRT (Evans et al., GCN Circ. 42908) and of the EP Follow-up X-ray Telescope (FXT) (Zhang et al., GCN Circ. 42915). We observed the field of EP251130a with one of the two Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Teide Observatory, Tenerife, Canary Islands, Spain. The observation, a single exposure of 500 sec in the SDSS i' filter, started on 2025-12-01 at 23:31:37 UT, about 36.40 hours after the EP-WXT trigger. The optical counterpart first reported by Dornic et al. (GCN Circ. 42904) is clearly detected in our image with a magnitude of i' = 20.68 +/- 0.14 (AB), calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical observations (Lipunov et al., GCN Circ. 42906; He et al., GCN Circ. 42914; Gupta et al., GCN Circ. 42916; Zheng et al., GCN Circ. 42917; van Dalen et al., GCN Circ. 42918; Moskvitin and Spiridonova, GCN Circ. 42919; Aryan et al., GCN Circ. 42921; Volnova et al., GCN Circ. 42922; Ma et al., GCN Circ. 42940; and Corcoran et al., GCN Circ. 42951). van Dalen et al. (GCN Circ. 42918) have reported a redshift of z = 4.035 using GTC OSIRIS+. 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/42963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41038] Fermi GRB 251202B: Global MASTER-Net observations report
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42962 SUBJECT: Fermi GRB 251202B: Global MASTER-Net observations report DATE: 25/12/02 19:00:24 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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251202B ( Fermi GBM team, GCN 42961) errorbox 566 sec after notice time and 598 sec after trigger time at 2025-12-02 18:37:01 UT, with upper limit up to 19.2 mag. Observations started at twilight. The observations began at zenith distance = 24 deg. The sun altitude is -12.7 deg. The galactic latitude b = -67 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=3058648 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 629 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 04m 42.90s , -23d 23m 21.3s) | C | 60 | 17.6 | 629 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 06m 42.31s , -23d 38m 56.2s) | C | 60 | 18.4 | 689 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 06m 42.31s , -23d 38m 56.2s) | C | 180 | 19.2 | Coadd 708 | 2025-12-02 18:38:20 | MASTER-SAAO | (23h 04m 42.92s , -23d 23m 16.2s) | C | 60 | 17.6 | 708 | 2025-12-02 18:38:20 | MASTER-SAAO | (23h 06m 42.32s , -23d 38m 51.7s) | C | 60 | 18.4 | 787 | 2025-12-02 18:39:39 | MASTER-SAAO | (23h 04m 42.96s , -23d 23m 12.1s) | C | 60 | 17.7 | 787 | 2025-12-02 18:39:40 | MASTER-SAAO | (23h 06m 42.35s , -23d 38m 48.1s) | C | 60 | 18.4 | 866 | 2025-12-02 18:40:58 | MASTER-SAAO | (23h 04m 43.00s , -23d 23m 08.4s) | C | 60 | 17.7 | 866 | 2025-12-02 18:40:58 | MASTER-SAAO | (23h 06m 42.37s , -23d 38m 45.0s) | C | 60 | 18.5 | 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/42962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41037] GRB 251202B: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42961 SUBJECT: GRB 251202B: Fermi GBM Final Real-time Localization DATE: 25/12/02 18:37:45 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 SHORT GRB At 18:27:03 UT on 2 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251202B (trigger 786392828.111108 / 251202769). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 347.2, Dec = -23.3 (J2000 degrees, equivalent to J2000 23h 08m, -23d 18'), with a statistical uncertainty of 4.5 degrees. The angle from the Fermi LAT boresight is 92.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41036] IPN triangulation of GRB 251129B (short/hard)
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42960 SUBJECT: IPN triangulation of GRB 251129B (short/hard) DATE: 25/12/02 18:31:26 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 251129B (AstroSat-CZTI detection: Salunke et al., GCN 42958) was detected by Konus-Wind, Swift(BAT), Mars-Odyssey (HEND), and AstroSat (CZTI), at about 35494 s UT (09:51:34). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 124.862 (08h 19m 27s) +76.391 (+76d 23' 28") Corners: 118.469 (07h 53m 53s) +78.048 (+78d 02' 53") 119.970 (07h 59m 53s) +77.774 (+77d 46' 26") 129.621 (08h 38m 29s) +74.606 (+74d 36' 22") 128.692 (08h 34m 46s) +74.931 (+74d 55' 51") --------------------------------------------- The error box area is 617 sq. arcmin, and its maximum dimension is 4.32 deg (the minimum one is 2.6 arcmin). The Sun distance was 117 deg. The localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB251129_T35496/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/42960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41035] GRB251129A/EP251129a: Swift UVOT detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42959 SUBJECT: GRB251129A/EP251129a: Swift UVOT detection DATE: 25/12/02 18:31:14 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and B. Cenko (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of GRB 251129A 16.8 ks after the SVOM trigger (Tan et al., GCN Circ. 42877). GRB251129A was also detected by the EP (Wu et al, GCN Circ. 16828). The optical afterglow consistent with the SVOM/COLIBRI position (Angulo et al. GCN Circ. 42880; Watson, GCN Circ. 42883) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:: Filter T_start(s) T_stop(s) Exp(s) Mag white 16828 17147 315 19.63 +/- 0.07 white 27564 28089 502 19.69 +/- 0.12 white 111007 117142 1044 20.22 +/- 0.12 white 227072 234439 2745 20.92 +/- 0.17 u 16503 16823 315 20.06 +/- 0.30 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41034] GRB251129A/EP251129a: Swift UVOT detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42959 SUBJECT: GRB251129A/EP251129a: Swift UVOT detection DATE: 25/12/02 18:31:14 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and B. Cenko (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of GRB 251129A 16.8 ks after the SVOM trigger (Tan et al., GCN Circ. 42877). GRB251129A was also detected by the EP (Wu et al, GCN Circ. 16828). The optical afterglow consistent with the SVOM/COLIBRI position (Angulo et al. GCN Circ. 42880; Watson, GCN Circ. 42883) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:: Filter T_start(s) T_stop(s) Exp(s) Mag white 16828 17147 315 19.63 +/- 0.07 white 27564 28089 502 19.69 +/- 0.12 white 111007 117142 1044 20.22 +/- 0.12 white 227072 234439 2745 20.92 +/- 0.17 u 16503 16823 315 20.06 +/- 0.30 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41033] GRB 251129B: AstroSat CZTI detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42958 SUBJECT: GRB 251129B: AstroSat CZTI detection DATE: 25/12/02 18:22:35 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short-duration GRB 251129B which was also detected by Konus Wind (IPN Notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a peak of emission with the strongest peak at 2025-11-29T09:51:34 UTC. The measured peak count rate associated with the burst is 1480 (+927, -83) counts/s above the background in the combined data of three quadrants (out of four), with a total of 128 (+30, -29) counts. The local mean background count rate was 212 (+20, -44)) counts/s. Using cumulative rates, we measure a T90 of 0.14 (+0.04, -0.03) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42958. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41032] GRB 251202A: Fermi GBM Observation
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42957 SUBJECT: GRB 251202A: Fermi GBM Observation DATE: 25/12/02 16:57:29 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:50:52.31 UT on 02 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251202A (GCN trigger 786333057/251202077), which was also detected by Einstein Probe (Y. J. Zhang et al. 2025, GCN 42937), Swift XRT (B. Sbarufatti et al. 2025, GCN 42943), Swift UVOT (N.P.M. Kuin et al. 2025, GCN 42956) GOTO (D. O’Neill et al. 2025, GCN 42947) and LCO (J. Quirola-Vasquez et al. 2025, GCN 42948). The spectroscopic redshift of GRB 251202A is found to be 2.785 by NOT (Z.P. Zhu et al. 2025, GCN 42939). The Fermi GBM Final Real-time Localization (GCN 42933) is consistent with the position reported by other instruments. The angle from the Fermi LAT boresight is 73 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 43 s (50-300 keV). The time-averaged spectrum from T0-10 to T0+55 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.07 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 350 +/- 50 keV. The event fluence (10-1000 keV) in this time interval is (9.9 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+8.8 s in the 10-1000 keV band is 4.2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/42957. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41031] GRB 251202A: Swift/UVOT Detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42956 SUBJECT: GRB 251202A: Swift/UVOT Detection DATE: 25/12/02 16:35:43 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of EP251202a/GRB 251202A 17,500s after the EP trigger (Zhang et al., GCN Circ. No 42937). A source consistent with Li et al. (GCN Circ No 42934) and the XRT position (Sbarufatti et al. GCN Circ. No. 42943) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 08:08:27.5 = 122.11420 (deg.) Dec (J2000) = 40:36:45.3 = 40.61244 (deg.) with an estimated uncertainty of 0.48 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 u 17500 18104 509 19.80 +/- 0.20 u 23697 24044 342 20.26 +/- 0.39 u 28710 28841 129 20.06 +/- 0.53 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.043 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42956. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41030] GRB 251201B: Kilonova-Catcher optical afterglow detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42955 SUBJECT: GRB 251201B: Kilonova-Catcher optical afterglow detection DATE: 25/12/02 16:14:17 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Freeberg (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 251201B detected by Swift/BAT (Moss et al., GCN 42924) and Fermi/GBM (Fermi GBM team, GCN 42923) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iTelescope 72 located in Chile and operated by M. Freeberg. Our observations started at TGRB+8.4h and were taken with Rc filter. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical counterpart reported by Swift/UVOT(Moss et al., GCN 42924, Kuin et al., GCN 42954), LCO/1m (Cerón et al., GCN 42929), MASTER (Buckley et al., GCN 42930), SVOM/VT (Li et al., GCN 42931). We report our follow-up results in the table below: +---------------+-----------+-----------+----------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+=============+ | 8.89 | 17 x 180s | Rc (Vega) | 20.33 +/- 0.09 | iT72 | +---------------+-----------+-----------+----------------+-------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Johnson-Cousins filters were calibrated using the GAIA DR3 Synphot catalog. 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/42955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41029] GRB 251201B: Swift/UVOT Detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42954 SUBJECT: GRB 251201B: Swift/UVOT Detection DATE: 25/12/02 15:52:28 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251201B 101 s after the BAT trigger (Moss et al., GCN Circ. 42924). A source consistent with the XRT position is detected in the initial UVOT exposures. 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 101 251 147 17.31 +/- 0.03 v 644 663 19 15.97 +/- 0.12 b 570 589 20 16.71 +/- 0.10 u 314 564 246 16.48 +/- 0.04 w1 693 1808 117 18.35 +/- 0.18 m2 668 1093 39 >18.7 w2 1196 1562 39 >18.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.008 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42954. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41028] GRB 251130B: Glowbug gamma-ray detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42953 SUBJECT: GRB 251130B: Glowbug gamma-ray detection DATE: 25/12/02 15:52:05 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 251130B, which was also detected by Fermi/GBM (GCN 42905, 42907) and AstroSat/CZTI (GCN 42925). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-30 15:33:27.216 with a duration of 82.0 s and a total significance of about 31.8 sigma. The light curve comprises an initial broad peak at ~T0+1s, a narrow peak ~T0+19s, followed by a dominant peak at ~T0+70s. An excess at the Fermi/GBM trigger time (15:33:18) may be present in the Glowbug data at low significance. 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/42953. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41027] GRB 251201B: GECAM-B observation of a long burst
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42952 SUBJECT: GRB 251201B: GECAM-B observation of a long burst DATE: 25/12/02 15:41:14 GMT FROM: Yue Wang <m18509381757(a)163.com> Yue Wang, Chen-Wei Wang, Hao-Xuan Guo, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 251201B, at 2025-12-01T16:26:32.950 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #42923). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a long pulse with a duration (T90) of 65 +6/-5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251201B.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42952. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41026] EP251130a: continued NOT optical observations indicate steep fading phase
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42951 SUBJECT: EP251130a: continued NOT optical observations indicate steep fading phase DATE: 25/12/02 15:26:45 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> G. Corcoran (UCD), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), R. H. Rasmussen (NOT and Aarhus) report on behalf of a larger collaboration. We continued the monitoring of the optical counterpart (Dornic et al., GCN 42904; Evans et al., GCN 42908; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917; van Dalen et al., GCN 42918; Moskvitin et al., GCN 42919; Aryan et al., GCN 42921; Volnova et al., GCN 42922; Ma et al., GCN 42940) of EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations consisted of two epochs, the first consisting of 3 x 300 s exposures in SDSS-i and 5 x 200 s exposures in SDSS-z starting at 2025-12-01T23:32:00, with the second epoch being a repeat of the first i-band observation starting at 2025-12-02T05:56:48. The source was detected in all stacked images. We calibrated our photometry using nearby stars from the Pan-STARRS catalog and did not correct for Galactic extinction. We obtain the following i-band photometry: epoch 1: i = 20.84 +/- 0.07 (mid time: 2025-12-01T23:42:39, ~1.52 days post trigger); epoch 2: i = 21.23 +/- 0.04 (mid time: 2025-12-02T06:07:27, ~1.79 days post trigger). These measurements show that the re-brightening reported by Zheng et al. (GCN 42917), van Dalen et al. (GCN 42918) and Moskvitin et al. (GCN 42919) seems to have finished and the light curve is fading quickly with a power-law decay index of ~2.2. Further observations are planned and encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/42951. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41025] GRB 251122A/EP251122a: CrAO ZTSh optical observations
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42950 SUBJECT: GRB 251122A/EP251122a: CrAO ZTSh optical observations DATE: 25/12/02 15:21:45 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), V. V. Rumyantsev (CrAO), A. S. Pozanenko (IKI), N. S. Pankov (IKI) report on behalf of IKI GRB-FuN collaboration: 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 ZTSH telescope of CrAO starting on 2025-11-11 (UT) 21:37:17 UT and taking several 120s exposures in R-band. The optical counterpart (Cheng et al., GCN 42803; Li et al., GCN 42806; Sun et al., GCN 42807; Ma et al., GCN 42811; Gupta et al., GCN 42813; Busmann et al., GCN 42814) is detected in the stacked frame. Preliminary photometry is the following: Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-22 21:37:17 0.34097 20*120 R 22.36 0.25 22.8 CrAO/ZTSh 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/42950. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41024] Fermi-LAT Gamma-ray Observations of IceCube-251130A
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42949 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-251130A DATE: 25/12/02 15:10:50 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC251130A neutrino event (GCN 42909) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-11-30 at 17:53:30.69 UTC (T0) with J2000 position RA = 229.70 (+0.53, -0.52) deg, Decl. = -5.53 (+0.58, -0.60) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC251130A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC251130A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC251130A best-fit position, the >100 MeV flux upper limit (95% confidence) is <5.5e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <8.7e-09 (<1.7e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/42949. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41023] EP251202a / GRB 251202A: LCO r- and i-band optical detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42948 SUBJECT: EP251202a / GRB 251202A: LCO r- and i-band optical detection DATE: 25/12/02 14:00:22 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> J. Quirola-Vasquez (Radboud), J. Sanchez-Sierras (Radboud), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), A. J. Levan (Radboud and Warwick), J. A. Chacón (PUC), F. E. Bauer (SSI and UTA), J. N. D. van Dalen (Radboud), A. P. C. van Hoof (Radboud) report on behalf of a larger collaboration: We observed the optical counterpart (Li et al., GCN 42934) of EP251202a (Zhang et al., GCN 42937, Liang et al., GCN 42946) and Fermi GRB 251202A (Fermi GBM team, GCN 42933) with a spectroscopic redshift of z = 2.785 (Zhu et al., GCN 42939) using the Las Cumbres Observatory (LCO) network at the McDonald Observatory, equipped with the SINISTRO camera. Observations were obtained in the r (6x200 s) and i (6x200 s) bands, starting on 2025-12-02 at 09:00:43 UTC (i.e., a mid-time observation of 7.35 and 7.75 hr after the EP/WXT trigger, respectively). Calibrated to nearby stars from the Pan-STARRS catalog, we measure AB magnitudes r = 19.22 +/- 0.06 and i = 19.12 +/- 0.06, not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42948. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41022] GRB 251202A: GOTO optical afterglow detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42947 SUBJECT: GRB 251202A: GOTO optical afterglow detection DATE: 25/12/02 13:55:02 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, S. Moran, G. Ramsay, R. Starling, B. P. Gompertz, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar and M. Pursiainen report on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the GRB 251202A (Fermi GBM team, GCN 42923; Einstein Probe, GCN 42937). Targeted observations were performed beginning at 2025-12-02 03:00:49 UT, (+1.19h post trigger). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. We detect the counterpart (Moss et al., GCN 42924; Osborne et al., GCN 42927; Goyal et al., GCN 42925; Li et al., GCN 42931; Sbarufatti et al. GCN 42943) with magnitude L = 17.92 ± 0.04 AB mag (+1.71h), before fading to L = 18.83 ± 0.07 AB mag (+4.3h). Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/42947. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41021] EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42946 SUBJECT: EP251202a/GRB 251202A: refined analysis of the EP-WXT observations DATE: 25/12/02 12:20:05 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R. D. Liang (NAOC) Z. M. Wang (BNU), Y. Wu (NJU), Y. J. Zhang (THU), H. N. Yang, H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251202a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 42937), and was followed by several telescopes (Li et al., GCN 42934, Lipunov et al., GCN 42938 and Zhu et al., GCN 42939, Sbarufatti et al. GCN 42943). The refined analysis of the WXT data shows that the event started at T0=2025-12-02T01:48:23.9 (UTC) and lasted for ~400 s. Three peaks are detected in the lightcurve, whose spectra are characterized by photon indice of 2.33 (-0.90/+1.02), 1.12 (-0.48/+0.60) and 1.19 (-0.51/+1.1), respectively. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 6.48 x 10^20 cm^-2 and a photon index of 1.23 (-0.19/+0.19). The derived average unabsorbed 0.5-4 keV flux is 5.40 (-0.63/+0.70) x 10^(-10) 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/42946. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41020] GRB 251201A: GECAM-B observation of a burst
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42945 SUBJECT: GRB 251201A: GECAM-B observation of a burst DATE: 25/12/02 12:08:00 GMT FROM: Yue Wang <m18509381757(a)163.com> Yue Wang, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 251201A, at 2025-12-01T04:37:04.100 UTC (denoted as T0), which is also detected by MAXI/GSC (MAXI team, GCN #42913) and SVOM/GRM (Yue Wang et al., GCN #42932). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses followed by a possible flare with a total T90 of 47.7 +/-15.6 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251201A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42945. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41019] GRB 251126A: SAO RAS optical marginal detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42944 SUBJECT: GRB 251126A: SAO RAS optical marginal detection DATE: 25/12/02 12:05:32 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova, V. Shergin (SAO RAS), A. Volnova (IKI), N. Pankov (HSE, IKI), A. 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; Barthelmy et al., GCN 42876) with the Zeiss-1000 1m telescope of the SAO RAS starting on 2025-11-30 (UT) 00:19:43. 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; Moskvitin et al, GCN 42870; Adami et al., GCN 42871; Pankov et al., GCN 42875; Goranskij et al., GCN 42896; Yao et al., GCN 42941) is marginally detected in the stacked frame with the following brightness. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-30 00:19:43 3.24019 13*300 Rc 24.3 0.4 24.3 The preliminary 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/42944. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41018] GRB 251202A: Swift-XRT afterglow detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42943 SUBJECT: GRB 251202A: Swift-XRT afterglow detection DATE: 25/12/02 11:00:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> B. Sbarufatti (INAF-OAB), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 251202A. We searched for X-ray sources in 759 s of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 759 s, obtained between T0+2.4 ks and T0+24.0 ks. An uncatalogued X-ray source are clearly detected within the Einstein Probe/WXT error region. Using 411 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 122.11512, +40.61228 which is equivalent to: RA (J2000): 08h 08m 27.63s Dec(J2000): +40d 36' 44.2" with an uncertainty of 2.4 arcsec (radius, 90% confidence). This position is 10.3 arcsec from the EP/FXT position (Zhang et al., GCN Circ. 42937) and 2.2 arcsec from the optical counterpart reported by Li et al. (GCN 42934). The light curve can be modelled with a power-law decay with a decay index of alpha=1.08 (+0.33, -0.24). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.93 (+0.45, -0.22). The best-fitting absorption column is consistent with the Galactic value of 6.5 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 3.4 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 6.5 x 10^20 cm^-2 Intrinsic column: 6 (+/-166) x 10^20 cm^-2 at z=2.785 Photon index: 1.93 (+0.45, -0.22) If the light curve continues to decay with a power-law decay index of 1.08, the count rate at T+24 hours will be 0.018 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.3 x 10^-13 (7.2 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/03000226. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/EP/EP_FIELD00086. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42943. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41017] EP251129a/GRB 251129A: NOWT Detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42942 SUBJECT: EP251129a/GRB 251129A: NOWT Detection DATE: 25/12/02 08:20:32 GMT FROM: Abdusamatjan Iskandar at XAO,CAS <abudu(a)xao.ac.cn> Shahidin Yaqup, Abdusamatjan Iskandar, Jinzhong Liu, report on behalf of optical group of the XAO: We imaged the field of the GRB 251129A/EP 251129a (GCN Circ. 42877, 42880, 42884 ) using the Nanshan One-meter Wide-field Telescope (NOWT) at Nanshan Station of Xinjiang Astronomical Observatory (XAO). We observed from 2025-11-29 20:08:26 to 20:32:43 UTC and obtained 6 x 300 s exposure in the V filter. The stack image photometry was calibrated using nearby stars from the GAIA synthesis catalog, without correction for Galactic extinction. We detect a source at the position (RA, DEC(J2000) = 14:57:18.88, +79:17:34.8) reported by GCN Circ.42880, with preliminary magnitude of V = 21.74+-0.64 mag. View this GCN Circular online at https://gcn.nasa.gov/circulars/42942. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41016] GRB 251126A: SVOM/VT optical observation
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42941 SUBJECT: GRB 251126A: SVOM/VT optical observation DATE: 25/12/02 06:57:14 GMT FROM: zhyao(a)bao.ac.cn Z. H. Yao, Y. L. Qiu, C. Wu, H. L. Li, Y. N. Ma, L. P. Xin, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC) and J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 251126A detected by Swift/BAT (Caputo et al., GCN 42843). SVOM/VT began observing the field at 2025-11-26T19:45:56.502 UTC, 35 minutes after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (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; 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 et al. 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; Pankov et al., GCN 42875; Goranskij et al. GCN 42896) was detected in both VT_B and VT_R band within BAT (Caputo et al., GCN 42843; Barthelmy et al. GCN 42876) and XRT's (Caputo et al., GCN 42843; Evans et al., GCN 42845; Goad et al., GCN 42851) error box.We detect a clear fading with a decay slope of approximately 1.6, followed by a rebrightening bump occurring at ~13.48 h after the trigger. The most recent photometric measurement is as follows: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|---------------- 25.34 | 20*70 | VT_B | 22.87+/-0.12 25.34 | 20*70 | VT_R | 21.64+/-0.05 Our photometry was not corrected for Galactic extinction. 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/42941. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41015] EP251130a: SVOM/VT optical observation
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42940 SUBJECT: EP251130a: SVOM/VT optical observation DATE: 25/12/02 06:52:47 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Y. L. Qiu, C. Wu, H. L. Li, L. P. Xin, Z. H. Yao, 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) report on behalf of the SVOM/VT team. SVOM performed a Target of Opportunity observation of EP251130a detected by EP/WXT (Wu et al., GCN 42903). SVOM/VT began observing the field at 2025-12-01T16:10:37 UTC, 29.05 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Dornic et al., GCN 42904; Lipunov et al., GCN 42906; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917; van Dalen et al., GCN 42918; Moskvitin and Spiridonova, GCN 42919; Aryan et al., GCN 42921; Volnova et al., GCN 42922) was detected within EP/FXT and Swift/XRT errorbox (Zhang et al., GCN 42915; Evans et al., GCN 42908) in both VT_B and VT_R bands. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 29.61 | 23*50 | VT_B | 22.8 | 0.3 29.61 | 23*50 | VT_R | 20.54 | 0.08 Our photometry was not corrected for Galactic extinction. 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/42940. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41014] EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42939 SUBJECT: EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785 DATE: 25/12/02 06:18:17 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> Z.P. Zhu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF/OACN and DARK/NBI), A. de Ugarte Postigo (LAM), D. Xu, X. Liu, S.Q. Jiang, J. An, L.B. He (NAOC), A. Saccardi (CEA/Irfu), R. H. Rasmussen (NOT and Aarhus) report on behalf of a large collaboration: We observed the optical counterpart (Li et al., GCN 42934) of EP251202a (Zhang et al., GCN 42937), which is likely the same event of Fermi GRB 251202A (Fermi GBM team, GCN 42933), using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera and spectrograph. We obtained 10x120 s and 9x120 s exposures in the r and z bands, respectively, starting on 2025 Dec 2 at 02:51:32 UT. The afterglow is clearly detected in single images, with an AB magnitude of r = 17.27 +/- 0.01 at a mid time of 1.05 hr after the trigger. A sequence of 3 spectra by 1200 s each was then acquired using grism #4, covering the wavelength range 3500-9500 AA. Our first spectrum started on 2025 Dec 2.156 UT (1.93 hr after the EP/WXT trigger). Continuum is detected across the whole wavelength range. A spectral break is detected around 4610 AA, and the onset of the forest is seen blueward of this wavelength. We match existing features to a low-column density Lyman alpha and C IV (unresolved) at z = 2.785, which we believe to be the redshift of the burst. Intervening systems are also seen in Lyman alpha and C IV at z = 2.450 and 2.356. We acknowledge the use of the grbspec.eu tool to analyse this spectrum. View this GCN Circular online at https://gcn.nasa.gov/circulars/42939. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41013] Fermi GRB 251202A: Global MASTER-Net observations report
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42938 SUBJECT: Fermi GRB 251202A: Global MASTER-Net observations report DATE: 25/12/02 03:30:34 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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251202A ( Fermi GBM team, GCN 42933) errorbox 570 sec after notice time and 604 sec after trigger time at 2025-12-02 02:00:56 UT, with upper limit up to 18.8 mag. Observations started at twilight. The observations began at zenith distance = 76 deg. The sun altitude is -15.8 deg. The galactic latitude b = 31 deg., longitude l = 177 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3057770 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 634 | 2025-12-02 02:00:56 | MASTER-SAAO | (07h 56m 46.47s , +43d 37m 13.0s) | C | 60 | 17.7 | 694 | 2025-12-02 02:00:56 | MASTER-SAAO | (07h 56m 46.46s , +43d 37m 13.0s) | C | 180 | 18.6 | Coadd 634 | 2025-12-02 02:00:56 | MASTER-SAAO | (07h 59m 07.79s , +43d 21m 09.1s) | C | 60 | 18.0 | 694 | 2025-12-02 02:00:56 | MASTER-SAAO | (07h 59m 07.80s , +43d 21m 09.1s) | C | 180 | 18.8 | Coadd 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/42938. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41012] EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42937 SUBJECT: EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient DATE: 25/12/02 03:28:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Zhang (THU), R. D. Liang (NAOC) Z. M. Wang (BNU), Y. Wu (NJU), H. N. Yang, H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251202a. The transient triggered EP-WXT (ID: 01709249064) at 2025-12-02T01:49:15 (UTC). The WXT position of the source is R.A. = 122.121 deg, DEC = 40.600 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The trigger time and the position of the transient is consistent with that of GRB 251202A detected by Fermi/GBM (GCN 42933). We performed a follow-up observation with the Follow-up X-ray Telescope (FXT), starting at 2025-12-02T02:09:51 (UTC), about 20 minutes after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 122.1190 deg, DEC = 40.6125 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). The position is 12 arcsec from the optical counterpart reported by Las Cumbres Observatory (Li et al., GCN 42934). 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/42937. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41011] GRB 251201B: Swift-XRT refined Analysis
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42936 SUBJECT: GRB 251201B: Swift-XRT refined Analysis DATE: 25/12/02 03:23:04 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Salvaggio (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 251201B, from 86 s to 23.3 ks after the trigger. The data comprise 362 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+6.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.6 (+/-0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.40 (+/-0.04). The best-fitting absorption column is 2.30 (+/-0.12) x 10^21 cm^-2, in excess of the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.93 (+0.16, -0.15) and a best-fitting absorption column of 10.0 (+4.5, -4.0) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 10.0 (+4.5, -4.0) x 10^20 cm^-2 Galactic foreground: 1.8 x 10^20 cm^-2 Excess significance: 3.4 sigma Photon index: 1.93 (+0.16, -0.15) If the light curve continues to decay with a power-law decay index of 1.6, the count rate at T+24 hours will be 3.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.5 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/01418729. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42936. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41010] IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42935 SUBJECT: IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/12/02 02:50:34 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-251130A (https://gcn.nasa.gov/circulars/42909) in a time range of 1000 seconds centered on the alert event time (2025-11-30 17:45:10.690 UTC to 2025-11-30 18:01:50.690 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-251130A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 4.2e-01 to 5.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251130A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 4e+02 GeV and 3e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-11-29 17:53:30.690 UTC to 2025-12-01 17:53:30.690 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 4.3e-01 to 5.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-251130A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/42935. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41009] The EP-WXT trigger 01709249064: Las Cumbres discovery of the optical counterpart
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42934 SUBJECT: The EP-WXT trigger 01709249064: Las Cumbres discovery of the optical counterpart DATE: 25/12/02 02:44:37 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of The EP-WXT trigger 01709249064 with a Las Cumbres 1m telescope at Teide Observatory, Tenerife, 18 mins after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w band. We find a uncataloged source at RA=122.1143 Dec=40.6123 within the EP/WXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 61011.089 Mag 15.6 We find a faint red likely extended source at this position in Legacy Survey data (https://www.legacysurvey.org/viewer) Additional followup is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/42934. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41008] GRB 251202A: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42933 SUBJECT: GRB 251202A: Fermi GBM Final Real-time Localization DATE: 25/12/02 02:01:27 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 01:50:52 UT on 2 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251202A (trigger 786333057.306028 / 251202077). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 120.3, Dec = 43.5 (J2000 degrees, equivalent to J2000 08h 01m, 43d 30'), with a statistical uncertainty of 2.8 degrees. The angle from the Fermi LAT boresight is 70.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202077/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202077/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202077/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42933. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41007] GRB 251201A: SVOM/GRM observation of a burst
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42932 SUBJECT: GRB 251201A: SVOM/GRM observation of a burst DATE: 25/12/02 01:33:14 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Wen-Jun Tan, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Maria Grazia BERNARDINI (INAF-OAB, LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 251201A (SVOM trigger reference: sb25120107) at 2025-12-01T04:37:04.500 (T0), which is also detected by MAXI/GSC (MAXI team, GCN #42913) and GECAM-B. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a multi-pulses followed by a possible flare with a total T90 of 39.3 +5.1/-1.8 s in the 15-5000 keV band, the T90 of the main emission is 4.1 +0.4/-0.2 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251201A.png In addition, the position of this burst, as determined by MAXI/GSC (RA=309.032, DEC=30.413, GCN #42913), is located at about 59 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-3 to T0+40 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.55 +0.15/-0.11 and the cutoff energy, parameterized as Epeak, is 352 +308/-144 keV. The event fluence (10-1000 keV) in this time interval is (5.32 +0.54/-0.58)E-06 erg/cm^2. The 1s peak spectrum, measured from T0-0.3 to T0+0.7 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.51 +0.11/-0.12 and the cutoff energy, parameterized as Epeak, is 154 +11/-9 keV. The flux (10-1000 keV) in this time interval is (1.71 +0.08/-0.07)E-06 erg/cm^2/s. The localization of GRB 251201A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251201A_amati.png The localization of GRB 251201A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251201A_yonetoku.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42932. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41006] GRB 251201B: SVOM/VT optical fading
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42931 SUBJECT: GRB 251201B: SVOM/VT optical fading DATE: 25/12/02 00:45:58 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H.L. Li, L.P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the field of GRB 251201B (Fermi GBM team, GCN 42923; Moss et al., GCN 42924; Osborne et al., GCN 42927; Goyal et al., GCN 42925). The observation stared at 2025-12-01T17:48:58 UTC, I.e., 1.4 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Cerón et al., GCN 42929;Buckley et al., GCN 42930) was detected Within the error box of Swift-UVOT (Moss et al., GCN 42924) and Swift-XRT (Osborne et al., GCN 42927). The position is at R.A., Dec. = 6.39414, -44.23374 degrees, equivalent to: R.A. (J2000) = 0:25:34.59 Dec. (J2000) = -44:14:01.46 with an uncertainty of 0.5 arcsec. The measurements in AB magnitude without correction for Galactic extinction are given below: Mid_time Band Exposure Time Magnitude (AB) 1.40 hours VT_B 70 sec 18.56+/-0.03 mag 1.40 hours VT_R 70 sec 18.08+/-0.03 mag 3.04 hours VT_B 70 sec 19.46+/-0.04 mag 3.04 hours VT_R 70 sec 18.97+/-0.04 mag It was fading with a slope of about -1.0 with a single power law. 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/42931. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41005] Swift GRB 251201B : MASTER optical counterpart detection
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42930 SUBJECT: Swift GRB 251201B : MASTER optical counterpart detection DATE: 25/12/01 23:18:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> D.Buckley (SAAO), V.M. Lipunov (Lomonosov MSU), A.Kuznetsov, I.Panchenko, G.Antipov, P.Balanutsa, K.Zhirkov, V.Senik, N. Tiurina, Ya.Kechin, A.Chasovnikov, D.Vlasenko, E.Gorbovskoy, Yu.Tselik(Lomonosov MSU, SAI, Moscow), O.A.Gress, N.M.Budnev, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); 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-SAAO robotic telescope of MASTER Global Robotic Net (Lipunov et al. [1-4], http://observ.pereplet.ru ), started Swift GRB 251201B (Moss et al GCN 42924, Osborne et al. GCN 42927) inspect at 2025-12-01 22:00:57 UT (20067s after trigger time), Lipunov et al. GCN 42929 There is optical counterpart MASTER OT J002534.28-441352.2 at Swift UVOT position (Moss et al. GCN 42924) with unfiltered m_OT~20.4m at summary image at 22:00:57 UT (420s exposition, mlim=21m). Real time updated cover map and OT position are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3054567 Observation and reduction will continue. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/42930. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41004] GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42929 SUBJECT: GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory DATE: 25/12/01 22:57:16 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> A. Cerón, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, 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. Pulido-Torres, 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 GRB 251201B by Fermi (Fermi GBM team, GCN Circ. 42923) and Swift (Moss et al., GCN Circ. 42924; Osborne et al., GCN Circ. 42927), we observed the field with one of the three Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Sutherland Observatory, South Africa. The observation, a single exposure of 300 sec in the SDSS r' filter, started on 2025-12-01 at 22:00:22 UT, about 5.73 hours after the Fermi and Swift trigger. The optical counterpart detected by Swift UVOT (Moss et al., GCN Circ. 42924) is clearly detected in our image with a magnitude of r' = 19.78 +/- 0.11 (AB), calibrated against the Legacy Imaging Surveys DR10 catalog and not corrected for Galactic extinction. 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/42929. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41003] Swift GRB 251201B: Global MASTER-Net observations report
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42928 SUBJECT: Swift GRB 251201B: Global MASTER-Net observations report DATE: 25/12/01 22:31:04 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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 251201B ( M. J. Moss et al., GCN 42924) errorbox 20045 sec after notice time and 20067 sec after trigger time at 2025-12-01 22:00:57 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 45 deg. The sun altitude is -35.7 deg. The galactic latitude b = -73 deg., longitude l = 317 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3057197 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 20158 | MASTER-SAAO | C | 180 | 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/42928. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41002] GRB 251201B: Enhanced Swift-XRT position
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42927 SUBJECT: GRB 251201B: Enhanced Swift-XRT position DATE: 25/12/01 21:24:42 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1078 s of XRT Photon Counting mode data and 3 UVOT images for GRB 251201B, 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 = 6.39463, -44.23233 which is equivalent to: RA (J2000): 00h 25m 34.71s Dec (J2000): -44d 13' 56.4" with an uncertainty of 3.8 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/42927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41001] EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42926 SUBJECT: EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations DATE: 25/12/01 18:59:42 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), A. S. Pozanenko (IKI), A. S. Moskvitin (SAO RAS), E. Klunko (ISTP), V. Rumyantsev (CrAO), M. Krugov (FAI), O. I. Spiridonnova (SAO RAS), N. S. Pankov (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the transient EP251118a (Jiang et al., GCN 42749) detected by the Einstein Probe Wide-field X-ray Telescope (EP WXT), with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) on Nov. 20 and 24 in R filter, with the ZTSH telescope of CrAO on Nov. 20 and 22 in B and R bands, with the AZT-20 1.5m telescope of Assy-Turgen observatory on Nov. 21 in Sloan r filter and Zeiss-1000 of SAO RAS on Nov. 30 in Rc-filter. The optical counterpart (Malesani et al., GCN 42751; Lipunov et al., GCN 42755; 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; Li et al., GCN 42776; Lee et al., GCN 42780; Moskvitin and Spiridonova, GCN 42785; Gupta et al., GCN 42787; Liu et al., GCN 42793; Aryan et al, GCN 42798; Gupta et al., GCN 42810) is detected in the stacked frame of each epoch. However the flux of the optical transient might be affected by the nearby red star SDSS J081239.57+105619.8 (r_SDSS = 21.911+/-0.178, g-r ~ 3 mag) located in 2.5 arcsec to the East. Some of our preliminary PSF photometry and observational details are the following: Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-20 18:58:01 2.12539 45*120 R 21.45 0.11 22.4 Mondy/AZT-33IK 2025-11-20 21:40:22 2.23886 42*120 R 21.29 0.10 23.2 CrAO/ZTSh 2025-11-20 23:13:01 2.31556 51*120 B 21.02 0.11 23.1 CrAO/ZTSh 2025-11-21 19:57:19 3.16164 57*60 r 22.39 0.08 23.8 Assy/AZT-20 2025-11-22 22:55:20 4.29925 48*120 R 21.62 0.17 22.5 CrAO/ZTSh 2025-11-24 19:51:39 6.15840 36*120 R 23.1 0.4 22.5 Mondy/AZT-33IK 2025-11-30 01:49:42 11.40863 12*300 Rc 22.90 0.15 24.0 SAO/Zeiss-1000 The photometry is calibrated using several nearby stars, USNO-B1.0 B2, R2 magnitudes for AZT-33IK, ZTSh and Zeiss-1000 data, and SDSS r magnitudes for AZT-20 data, all magnitudes are not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41000] GRB 251130B: AstroSat CZTI detection
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42925 SUBJECT: GRB 251130B: AstroSat CZTI detection DATE: 25/12/01 18:20:31 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Goyal (IITB), A. Arya (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 251130B which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42905). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-11-30T15:34:35 UTC. The measured peak count rate associated with the burst is 122 (+26, -28) counts/s above the background in the combined data of two quadrants (out of four), with a total of 467 (+165, -180) counts. The local mean background count rate was 139 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 11 (+5, -4) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-11-30T15:34:32 UTC. The measured peak count rate associated with the burst is 244 (+68, -42) counts/s above the background in the combined data of all quadrants, with a total of 1517 (+308, -325) counts. The local mean background count rate was 1246 (+7, -8) counts/s. We measure a T90 of 12 (+2, -3) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40999] GRB 251201B: Swift detection of a burst with an optical counterpart
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42924 SUBJECT: GRB 251201B: Swift detection of a burst with an optical counterpart DATE: 25/12/01 16:38:08 GMT FROM: Tyler Parsotan at NASA GSFC <tyler.parsotan(a)nasa.gov> M. J. Moss (GSFC), S. Dichiara (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team: At 16:26:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251201B (trigger=1418729). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 6.409, -44.237 which is RA(J2000) = 00h 25m 38s Dec(J2000) = -44d 14' 12" 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 40 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 16:28:03.7 UT, 93.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 6.3925, -44.2312 which is equivalent to: RA(J2000) = 00h 25m 34.20s Dec(J2000) = -44d 13' 52.3" with an uncertainty of 7.0 arcseconds (radius, 90% containment). This location is 47 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 0.1 s image was 8.63e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 101 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 00:25:34.59 = 6.39413 DEC(J2000) = -44:14:01.1 = -44.23364 with a 90%-confidence error radius of about 0.75 arc sec. This position is 9.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.28 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.008. Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com) 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/42924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40998] GRB 251201B: Fermi GBM Final Real-time Localization
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42923 SUBJECT: GRB 251201B: Fermi GBM Final Real-time Localization DATE: 25/12/01 16:37:01 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 16:26:24 UT on 1 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251201B (trigger 786299189.217446 / 251201685). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 13.8, Dec = -40.0 (J2000 degrees, equivalent to J2000 00h 55m, -40d 00'), with a statistical uncertainty of 1.1 degrees. The angle from the Fermi LAT boresight is 118.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251201685/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40997] EP251130a: Mondy optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42922 SUBJECT: EP251130a: Mondy optical observations DATE: 25/12/01 15:00:28 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), A. S. Pozanenko (IKI), E. Klunko (ISTP), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the X-ray transient EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915), also detected by Swift/XRT (Evans et al., GCN 42908) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting on 2025-11-30 (UT) 15:06:18 in R filter. The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914; Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al., GCN 42918; Moskvitin and Spiridonova, GCN 42919; Aryan et al., GCN 42921) is detected in the stacked frame. Preliminary photometry is the following: Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-30 15:06:18 0.18716 60*120 R 21.76 0.20 22.1 Mondy/AZT-33IK The photometry is calibrated using USNO-B1.0 stars from Moskvitin and Spiridonova, GCN 42919, and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40996] EP251130a: Optical detections with Kinder observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42921 SUBJECT: EP251130a: Optical detections with Kinder observations DATE: 25/12/01 14:51:58 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, T.-W. Chen, H.-Y. Hsiao, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915) using the 1m LOT and 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). The first epoch of r-band LOT observations began at 16:49 UTC on November 30, 2025 (MJD 61009.701), 5.70 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 clearly detected the optical counterpart (Dornic et al., GCN 42904; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917; van Dalen et al., GCN 42918; Moskvitin et al., GCN 42919). The optical counterpart lies within the Swift-XRT (Evans et al., GCN 42908) and the refined EP-FXT (Zhang et al., GCN 42915) localizations. Moreover, we utilized AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on stacked images. The details of the observations and the measured magnitudes (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61009.701 | 5.70 | 300 * 6 | 21.97 +/- 0.08 | 1".16 | 1.03 SLT | i | 61009.703 | 5.74 | 300 * 7 | 20.87 +/- 0.09 | 1".78 | 1.03 We plan to continue following the FXT on a few subsequent days. The presented magnitudes are calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al., 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinction of A_r = 0.26 mag and A_i = 0.19 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/42921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40995] SVOM GRB251201.19: Global MASTER-Net observations report
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42920 SUBJECT: SVOM GRB251201.19: Global MASTER-Net observations report DATE: 25/12/01 14:42:24 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 SVOM GRB251201.19 (trigger No 1764563824,22h 55m 57.19s , +47d 49m 47.3s, R=1) errorbox 35398 sec after notice time and 35428 sec after trigger time at 2025-12-01 14:27:33 UT, with upper limit up to 15.8 mag. Observations started at twilight. The observations began at zenith distance = 11 deg. The sun altitude is -9.2 deg. The galactic latitude b = -11 deg., longitude l = 104 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3056585 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 35459 | 2025-12-01 14:27:33 | MASTER-Kislovodsk | (22h 53m 50.26s , +48d 11m 12.3s) | C | 60 | 15.8 | 35459 | 2025-12-01 14:27:33 | MASTER-Kislovodsk | (23h 00m 39.53s , +47d 47m 53.5s) | C | 60 | 13.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/42920. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40994] EP251130a: SAO RAS optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42919 SUBJECT: EP251130a: SAO RAS optical observations DATE: 25/12/01 14:03:05 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova (SAO RAS) report on behalf of GRB follow-up team. We observed the field of the X-ray transient EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915), also detected by Swift-XRT (Evans et al., GCN 42908) with the Zeiss-1000 1m telescope of the SAO RAS on December 1, 01:29:21--03:08:47 UT (t_mid - T0 = 0.63281 days). We obtained 11 * 300 images in Rc band under mediocre weather conditions. The optical counterpart (Dornic et al., GCN 42904; He et al. GCN 42914; Gupta et al. GCN 42916; Zheng et al. GCN 42917; van Dalen et al., GCN 42918) is clearly detected in our stacked image with the brightness of R = 20.11 +/- 0.07 (R_lim = 21.8). This preliminary photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. USNO-B1 star RA DEC R2 1173-00161316 101.000000 +27.372589 16.26 1173-00161485 101.071981 +27.375787 16.76 1173-00161417 101.045348 +27.394953 16.04 In comparison with the OT brightness from 1.3m DFOT data (Gupta et al., GCN 42916) we noted a brightening between two epochs (also reported by Zheng et al. GCN 42917 and van Dalen et al., GCN 42918). View this GCN Circular online at https://gcn.nasa.gov/circulars/42919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40993] EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42918 SUBJECT: EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening DATE: 25/12/01 09:30:53 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> J. N. D. van Dalen (Radboud), A. P. C. van Hoof (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. Quirola-Vasquez (Radboud), P. G. Jonker (Radboud), D. Mata-Sanchez (IAC and ULL), N.C. Rodríguez (GTC), A. Cabrera-Lavers (GTC) report on behalf of a larger collaboration. We observed the counterpart (Dornic et al., GCN 42904; Evans et al., GCN 42908; He et al., GCN 42914; Gupta et al., GCN 42916; Zheng et al., GCN 42917) of EP251130a (Wu et al., GCN 42903; Zhang et al., GCN 42915) with the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. Three 1200 s exposures were obtained using the R1000R grating and a 1 arcsec slit. Observations began on 2025 Dec 1 at 01:28 UT, approximately 0.6 days after the EP trigger time. From the 60 s acquisition image taken in the i band, we measure a magnitude of i = 19.54+/-0.03 AB (calibrated against nearby Pan-STARRS objects). We find a rebrightening of the optical counterpart by ~1 mag in ~10 hr as compared to He et al. (GCN 42914). In the spectrum, a broad trough centered around 6120 AA is detected, which we interpret as due to a DLA. Several metal absorption lines are also detected on top of the bright continuum, which match Si II, Si II*, O I, C II, Si IV, C IV, Fe II, Al II, all at a common redshift of z = 4.035. View this GCN Circular online at https://gcn.nasa.gov/circulars/42918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40992] EP251130a: KAIT optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42917 SUBJECT: EP251130a: KAIT optical observations DATE: 25/12/01 09:16:17 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to EP251130a (Wu et al., GCN 42903) starting at 11:21:40 UT, 831 seconds after the burst. A set of 10x20s, 10x40s, 60x60s clear (roughly R) filter images were obtained. We clearly detected the optical afterglow (Dornic et al., GCN 42904, He et al., GCN 42914; Gupta et al., GCN 42916) in our coadd image. We measure its brightness decreased from 19.6 +/- 0.1 mag (Vega; mid time 16.45 min) to 20.2 +/- 0.2 mag (mid time of 91.03 min) with a decay index of 0.46. Additional 30x60s clear filter images were obtained the following night at a mid time of 0.89 days after the burst. The OT is still detected at 19.7 +/- 0.1 mag, indicating the OT has brightened. More follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/42917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40991] EP251130A: Optical observation from 1.3m DFOT
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42916 SUBJECT: EP251130A: Optical observation from 1.3m DFOT DATE: 25/12/01 08:45:09 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debalina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251130A detected by Einstein Probe (Wu et al. 2025, GCN 42903) 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 22025-11-30 at 19:21:24 UT, i.e., ~8.22 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 the optical counterpart in our stacked image within the error box of Swift-XRT (Evans et al. 2025, GCN 42908). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-30 19:21:24 ~8.22 R 300*12 22.20+/- 0.09 Our detection is consistent with Dornic et al. 2025 (GCN 42904); Lipunov et al. 2025 (GCN 42906); He et al. 2025 (GCN 42914). 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/42916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40990] EP251130A: Optical observation from 1.3m DFOT
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42916 SUBJECT: EP251130A: Optical observation from 1.3m DFOT DATE: 25/12/01 08:45:09 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debalina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251130A detected by Einstein Probe (Wu et al. 2025, GCN 42903) 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 22025-11-30 at 19:21:24 UT, i.e., ~8.22 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 the optical counterpart in our stacked image within the error box of Swift-XRT (Evans et al. 2025, GCN 42908). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-30 19:21:24 ~8.22 R 300*12 22.20+/- 0.09 Our detection is consistent with Dornic et al. 2025 (GCN 42904); Lipunov et al. 2025 (GCN 42906); He et al. 2025 (GCN 42914). 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/42916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40989] EP251130a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42915 SUBJECT: EP251130a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/12/01 08:40:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> W. J. Zhang (NAO, CAS), H. C. Ding, T. Wu (AHNU), Y. H. Jiang, Y. Wu (NJU), Y. Wang (PMO), Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP251130a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wu et al., GCN 42903), and was followed by several telescopes (Dornic et al., GCN 42904, Lipunov et al., GCN 42906 and Evans et al., GCN 42908). The refined analysis of the WXT data shows that the event started at T0=2025-11-30T11:04:00 (UTC) and lasted for ~230 s, 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 1.40 x 10^21 cm^-2 and a photon index of 1.54 (-0.63/+0.70). The derived average unabsorbed 0.5-4 keV flux is 2.46 (-0.77/+1.06) x 10^(-10) erg/s/cm^2. A follow-up observation of EP251130a with the Follow-up X-ray Telescope (FXT) was performed automatically at 2025-11-30T11:11:12 (UTC), about 7 minutes after T0, with an exposure time of 4,200 s. The on-ground analysis shows that an uncatalogued source was detected at R.A. = 101.0210 deg, Dec. = 27.3840 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). This position is ~1.6 arcsec from the reported optical counterpart (Dornic et al., GCN 42904). The average FXT 0.5-10 keV spectrum of the observation can be fitted with an absorbed power law, with a hydrogen column density of 1.39 (-0.81/+0.86) x 10^21 cm^-2 and a photon index of 2.12 (-0.32/+0.34). The derived average unabsorbed 0.5-10 keV flux is 3.32 (-0.31/+0.32) x 10^(-12) erg/s/cm^2. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/42915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40988] EP251130a: JinShan optical observations
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42914 SUBJECT: EP251130a: JinShan optical observations DATE: 25/12/01 06:43:09 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, J. An, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei, H.Z. Wu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of EP251130a (Wu et al., GCN 42903) using the 100B telescope of the JinShan project, located at Altay, Xinjiang, China. Obervations started at 2025-11-30 14:13:38 UT, i. e. 3.1 hrs post-burst, and a series of frames in g, r and i bands were obtained. The previously reported optical counterpart candidate (Dornic et al., GCN 42904) was detected in our stacked i-band frame with a magnitude i = 20.60 +/- 0.18 at a mid-time 4.67 hrs post-burst. The magnitude was callibrated with nearby PanSTARRS1 dr2 catalog and without the Galactic extinction correction. We acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40987] GRB 251201A: MAXI/GSC detection
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42913 SUBJECT: GRB 251201A: MAXI/GSC detection DATE: 25/12/01 05:57:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> D. Iijima, Y. Kawakubo (AGU), M. Nakajima (Nihon U.), H. Negoro, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 04:36:59 UT on December 1, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (309.032 deg, 30.413 deg) = (20 36 07, +30 24 46) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.20 deg and 0.16 deg, respectively. The roll angle of long axis from the north direction is 14.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 327 +- 36 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (307.993, 30.840) deg = (20 31 58, +30 50 23) (J2000) (R.A., Dec) = (307.875, 30.457) deg = (20 31 29, +30 27 25) (J2000) (R.A., Dec) = (310.227, 29.897) deg = (20 40 54, +29 53 49) (J2000) (R.A., Dec) = (310.354, 30.278) deg = (20 41 24, +30 16 40) (J2000) There was no significant excess flux in the previous transit at 03:04 UT. View this GCN Circular online at https://gcn.nasa.gov/circulars/42913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40986] GRB 251129A / EP251129a: SVOM/VT optical fading
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42887 SUBJECT: GRB 251129A / EP251129a: SVOM/VT optical fading DATE: 25/11/29 05:41:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li , L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), W. J. Tan (IHEP), D. F. Kong (GXU) report on behalf of the SVOM/VT team. SVOM/VT performed an automatic slew to GRB 251129A/EP251129a triggered by SVOM/ECL (sb25112901, Tan et al., GCN 42879). The burst was also triggered by EP (Wu et al., GCN 42884). SVOM/VT began the observation at 2025-11-29T02:43:03 UTC, i.e., 658 seconds post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With the downloaded early X band data, the optical counterpart (Angulo et al. GCN 42880; Watson, GCN 42883; Wu et al., GCN 42882; Masi et al. GCN 42885) was clearly detected in both channels. The measurements are given below: Mid_time Band Exposure Time Magnitude (AB) 12.43 min VT_B 50 sec 18.16+/-0.03 mag 12.43 min VT_R 50 sec 17.89+/-0.03 mag 44.96 min VT_B 50 sec 19.11+/-0.04 mag 44.96 min VT_R 50 sec 18.80+/-0.03 mag It was fading with a slope of about 0.7 with a single power law. Our photometry was not corrected for Galactic extinction. 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/42887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40985] EP251130a: COLIBRÍ optical counterpart candidate
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42904 SUBJECT: EP251130a: COLIBRÍ optical counterpart candidate DATE: 25/11/30 15:18:49 GMT FROM: Damien Dornic <ddornic(a)km3net.de> Damien Dornic (CPPM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), William H. Lee (UNAM), Kin Ramandeep Gill (UNAM), Noémie Globus (UNAM), Ocelotl López (UNAM), Diego López-Cámara (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the EP251130a (Wu et al., GCN 42903) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-30T12:09:17 to 12:28 UTC (from 1.02 to 1.34 hours after the trigger) and obtained 16 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we detect an uncatalogued source at the coordinates: RA = 101.0205 deg, Dec = 27.3840 deg with an uncertainty of 0.5 arcsec, compatible with the EP/FXT position (Wu et al., GCN 42903), at preliminary magnitudes of: r = 20.69 +/- 0.03 z = 19.45 +/- 0.03 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/42904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40984] Fermi GRB 251130B: Global MASTER-Net observations report
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42912 SUBJECT: Fermi GRB 251130B: Global MASTER-Net observations report DATE: 25/12/01 02:15:34 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 251130B ( Fermi GBM team, GCN 42905) errorbox 31683 sec after notice time and 31712 sec after trigger time at 2025-12-01 00:21:50 UT, with upper limit up to 16.3 mag. The observations began at zenith distance = 79 deg. The sun altitude is -43.2 deg. The galactic latitude b = -19 deg., longitude l = 255 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3056013 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 31742 | 2025-12-01 00:21:50 | MASTER-Kislovodsk | (06h 49m 44.31s , -34d 43m 17.4s) | C | 60 | 16.3 | 31742 | 2025-12-01 00:21:50 | MASTER-Kislovodsk | (06h 44m 55.88s , -34d 22m 49.2s) | C | 60 | 15.0 | 31822 | 2025-12-01 00:23:10 | MASTER-Kislovodsk | (07h 04m 25.10s , -34d 44m 07.1s) | C | 60 | 15.9 | 31822 | 2025-12-01 00:23:10 | MASTER-Kislovodsk | (06h 59m 36.92s , -34d 23m 35.3s) | C | 60 | 14.8 | 31902 | 2025-12-01 00:24:29 | MASTER-Kislovodsk | (06h 40m 40.37s , -32d 51m 33.0s) | C | 60 | 16.1 | 31902 | 2025-12-01 00:24:29 | MASTER-Kislovodsk | (06h 35m 57.97s , -32d 31m 06.6s) | C | 60 | 14.6 | 31982 | 2025-12-01 00:25:49 | MASTER-Kislovodsk | (07h 19m 00.02s , -34d 44m 45.6s) | C | 60 | 14.7 | 31982 | 2025-12-01 00:25:49 | MASTER-Kislovodsk | (07h 14m 12.41s , -34d 24m 10.5s) | C | 60 | 13.7 | 32061 | 2025-12-01 00:27:09 | MASTER-Kislovodsk | (06h 54m 58.67s , -32d 49m 48.0s) | C | 60 | 16.3 | 32061 | 2025-12-01 00:27:09 | MASTER-Kislovodsk | (06h 50m 16.82s , -32d 29m 18.5s) | C | 60 | 15.0 | 32141 | 2025-12-01 00:28:29 | MASTER-Kislovodsk | (07h 09m 15.84s , -32d 50m 53.6s) | C | 60 | 15.8 | 32141 | 2025-12-01 00:28:29 | MASTER-Kislovodsk | (07h 04m 33.40s , -32d 30m 27.1s) | C | 60 | 14.2 | 32221 | 2025-12-01 00:29:49 | MASTER-Kislovodsk | (07h 28m 45.67s , -34d 22m 42.6s) | C | 60 | 13.4 | 32381 | 2025-12-01 00:32:28 | MASTER-Kislovodsk | (06h 26m 31.94s , -32d 51m 09.2s) | C | 60 | 15.2 | 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/42912. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40983] GRB 251127A: SVOM/GRM observation
by GCN Circulars 01 Dec '25

01 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42911 SUBJECT: GRB 251127A: SVOM/GRM observation DATE: 25/12/01 02:08:58 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Zheng-Hang Yu, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 251127A at 2025-11-27T03:17:44.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #42852) and Glowbug (C.C. Cheung et al., GCN #42872). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of mutiple peaks with a T90 of 17.5 +4.0/-2.5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251127A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 155.6, DEC= 30.2, GCN#42852), is located at about 46 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-2 to T0+18 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.09 +0.22/-0.21 and the cutoff energy, parameterized as Epeak, is 267 +251/-77 keV. The event fluence (10-1000 keV) in this time interval is (1.05 +0.11/-0.11)E-05 erg/cm^2. The 1s peak spectrum, measured from T0-1 to T0 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.01 +0.18/-0.16 and the cutoff energy, parameterized as Epeak, is 591 +503/-197 keV. The flux (10-1000 keV) in this time interval is (7.84 +0.88/-1.01)E-07 erg/cm^2/s. The localization of GRB 251127A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251127A_amati.png The localization of GRB 251127A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251127A_yonetoku.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42911. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40982] IceCube Alert 251130.75: Global MASTER-Net observations report
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42910 SUBJECT: IceCube Alert 251130.75: Global MASTER-Net observations report DATE: 25/11/30 23:13:22 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the IceCube Alert 251130.75 (trigger No 31953389,15h 18m 58.08s , -05d 39m 25.2s, R=0.95) errorbox 18825 sec after notice time and 18880 sec after trigger time at 2025-11-30 23:08:10 UT, with upper limit up to 15.1 mag. Observations started at twilight. The observations began at zenith distance = 82 deg. The sun altitude is -14.8 deg. The galactic latitude b = 41 deg., longitude l = 356 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3056129 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 18910 | 2025-11-30 23:08:10 | MASTER-Tunka | (15h 18m 34.03s , -05d 47m 52.8s) | C | 60 | 14.5 | 18910 | 2025-11-30 23:08:10 | MASTER-Tunka | (15h 18m 53.09s , -05d 55m 00.3s) | C | 60 | 15.1 | 18984 | 2025-11-30 23:09:24 | MASTER-Tunka | (15h 18m 39.40s , -05d 48m 55.2s) | C | 60 | 14.3 | 18984 | 2025-11-30 23:09:24 | MASTER-Tunka | (15h 18m 58.71s , -05d 56m 07.2s) | C | 60 | 15.0 | 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/42910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40981] IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42909 SUBJECT: IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/11/30 19:37:39 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-11-30 at 17:53:30.69 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.1099 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141654_31953389.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-11-30 Time: 17:53:30.69 UT RA: 229.7 (+0.53/-0.52 deg 90% PSF containment) J2000 Dec: -5.53 (+0.58/-0.6 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/42909. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40980] EP251130a: Swift-XRT counterpart detection
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42908 SUBJECT: EP251130a: Swift-XRT counterpart detection DATE: 25/11/30 19:00:56 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 EP251130a, collecting 2.0 ks of Photon Counting (PC) mode data between T0+5.8 ks and T0+11 ks after the trigger. A likely counterpart has been found. The details of this source are: Source 1 (SWIFT J064404.8+272302): ================================== RA (J2000.0): 101.0203 = 06 44 04.87 Dec (J2000.0): +27.3839 = +27 23 02.0 Error: 3.9 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 75 arcsec from the Einstein Probe/WXT position. Mean rate: 0.0618 [+0.0070, -0.0068] ct s^-1 Mean flux: (2.21 [+0.25, -0.24])e-12 erg cm^-2 s^-1 Peak rate: 0.139 +/- 0.031 ct s^-1 Peak flux: (5.0 +/- 1.1)e-12 erg cm^-2 s^-1 ECF: 3.57e-11 erg cm^-2 ct^-1 assuming NH=1.80e+21 cm^-2, gamma=1.97 determined from a spectral fit. XMM UL: 3.5e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 1.4-sigma above this 3-sigma upper limit. The source may be fading, at the 2.6-sigma level. This position is consistent with the candidate optical counterpart reported by COLIBRI (GCN 42904). 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_FIELD00085. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42908. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40979] GRB 251130B: Fermi GBM Final Localization Correction
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42907 SUBJECT: GRB 251130B: Fermi GBM Final Localization Correction DATE: 25/11/30 18:45:22 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely LONG GRB "At 15:33:18.11 UT on 30 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251130B (trigger 786209603/251130648). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.82, Dec = -43.31 (J2000 degrees, equivalent to J2000 5h 15m, –43d 18'), with a statistical uncertainty of 1.74 degrees. The angle from the Fermi LAT boresight is 94 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40978] GRB 251130B: Fermi GBM Final Localization Correction
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42907 SUBJECT: GRB 251130B: Fermi GBM Final Localization Correction DATE: 25/11/30 18:45:22 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely LONG GRB "At 15:33:18.11 UT on 30 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251130B (trigger 786209603/251130648). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.82, Dec = -43.31 (J2000 degrees, equivalent to J2000 5h 15m, –43d 18'), with a statistical uncertainty of 1.74 degrees. The angle from the Fermi LAT boresight is 94 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40977] GRB 251130B: Fermi GBM Final Localization Correction
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42907 SUBJECT: GRB 251130B: Fermi GBM Final Localization Correction DATE: 25/11/30 18:45:22 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely LONG GRB "At 15:33:18.11 UT on 30 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251130B (trigger 786209603/251130648). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.82, Dec = -43.31 (J2000 degrees, equivalent to J2000 5h 15m, –43d 18'), with a statistical uncertainty of 1.74 degrees. The angle from the Fermi LAT boresight is 94 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40976] EP251130a: Global MASTER-Net observations report
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42906 SUBJECT: EP251130a: Global MASTER-Net observations report DATE: 25/11/30 16:45:38 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 EP251130a ( EP Team et al., GCN 42903) errorbox 16211 sec after notice time and 19018 sec after trigger time at 2025-11-30 16:24:47 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 80 deg. The sun altitude is -30.0 deg. The galactic latitude b = 11 deg., longitude l = 188 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3055832 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 19048 | 2025-11-30 16:24:47 | MASTER-Kislovodsk | (06h 42m 49.31s , +27d 04m 35.5s) | C | 60 | 13.6 | 19048 | 2025-11-30 16:24:47 | MASTER-Kislovodsk | (06h 42m 50.47s , +27d 27m 17.4s) | C | 60 | 15.3 | 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/42906. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40975] GRB 251130B: Fermi GBM Final Real-time Localization
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42905 SUBJECT: GRB 251130B: Fermi GBM Final Real-time Localization DATE: 25/11/30 15:43:48 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 15:33:18 UT on 30 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251130B (trigger 786209603.108754 / 251130648). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 102.1, Dec = -45.5 (J2000 degrees, equivalent to J2000 06h 48m, -45d 30'), with a statistical uncertainty of 11.5 degrees. The angle from the Fermi LAT boresight is 108.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130648/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42905. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40974] EP251030a: COLIBRÍ optical counterpart candidate
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42904 SUBJECT: EP251030a: COLIBRÍ optical counterpart candidate DATE: 25/11/30 15:18:49 GMT FROM: Damien Dornic <ddornic(a)km3net.de> Damien Dornic (CPPM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), William H. Lee (UNAM), Kin Ramandeep Gill (UNAM), Noémie Globus (UNAM), Ocelotl López (UNAM), Diego López-Cámara (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the EP251030a (Wu et al., GCN 42903) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-30T12:09:17 to 12:28 UTC (from 1.02 to 1.34 hours after the trigger) and obtained 16 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we detect an uncatalogued source at the coordinates: RA = 101.0205 deg, Dec = 27.3840 deg with an uncertainty of 0.5 arcsec, compatible with the EP/FXT position (Wu et al., GCN 42903), at preliminary magnitudes of: r = 20.69 +/- 0.03 z = 19.45 +/- 0.03 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/42904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40973] EP251130a: Einstein Probe detection of an X-ray transient
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42903 SUBJECT: EP251130a: Einstein Probe detection of an X-ray transient DATE: 25/11/30 11:51:35 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Wu, H. C. Ding (AHNU), Y. H. Jiang, Y. Wu (NJU), Y. Wang (PMO), 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 EP251130a. The transient triggered EP-WXT (ID: 01709249022) at 2025-11-30T11:07:49 (UTC). The WXT position of the source is R.A. = 101.041 deg, DEC = 27.394 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. = 101.0242 deg, DEC = 27.3824 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/42903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40972] EP251129a/GRB 251129A: EP-FXT follow-up observations
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42902 SUBJECT: EP251129a/GRB 251129A: EP-FXT follow-up observations DATE: 25/11/30 06:51:00 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang, Y. Wu, 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: A follow-up observation of EP251129a / GRB 251129A (Wu et al., GCN 42884, Tan et al., GCN 42877) with the Follow-up X-ray Telescope (FXT) was performed automatically at 2025-11-29T03:16:08 (UTC), i.e. T0+2643 s, where T0 is reported by SVOM (Tan et al., GCN 42877) , with an exposure time of 5,003 s. The average FXT 0.5-10 keV spectrum of the observation can be fitted with an absorbed power law, with a fixed Galactic hydrogen column density of 2.94 x 10^20 cm^-2, an intrinsic hydrogen column density of 1.40 (-0.05/+0.05) x 10^22 cm^-2, and a photon index of 1.98 (-0.02/+0.02) . The derived average unabsorbed 0.5-10 keV flux is 1.74 (-0.02/+0.02) x 10^(-9) erg/s/cm^2. We performed two target-of-opportunity (ToO) follow-up observations with FXT at 2025-11-29T05:26:09 (UTC, T0+10,444 s) and 2025-11-29T12:34:30 (UTC, T0+36,145 s), with an exposure time of 2,786 s and 3,091 s, respectively. The average FXT 0.5-10 keV spectrum of the first ToO observation can be fitted with an absorbed power law, with a fixed Galactic hydrogen column density of 2.94 x 10^20 cm^-2, an intrinsic hydrogen column density of 1.04 (-0.11/+0.11) x 10^22 cm^-2, and a photon index of 2.45 (-0.05/+0.05) . The derived average unabsorbed 0.5-10 keV flux is 1.56 (-0.04/+0.04) x 10^(-10) erg/s/cm^2. The average FXT 0.5-10 keV spectrum of the second ToO observation can be fitted with an absorbed power law, with a fixed Galactic hydrogen column density of 2.94 x 10^20 cm^-2, an intrinsic hydrogen column density of 1.49 (-0.46/+0.46) x 10^22 cm^-2, and a photon index of 3.49 (-0.23/+0.23). The derived average unabsorbed 0.5-10 keV flux is 9.20 (-0.75/+0.82) 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/42902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40971] GRB 251130A: Fermi GBM Final Real-time Localization
by GCN Circulars 30 Nov '25

30 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42901 SUBJECT: GRB 251130A: Fermi GBM Final Real-time Localization DATE: 25/11/30 00:53:39 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 00:43:07 UT on 30 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251130A (trigger 786156192.430142 / 251130030). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 176.6, Dec = -60.4 (J2000 degrees, equivalent to J2000 11h 46m, -60d 23'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 99.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130030/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130030/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251130030/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42901. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40970] GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42900 SUBJECT: GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460 DATE: 25/11/29 20:56:25 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> R. Sanchez-Ramirez, A. J. Castro-Tirado, S. Guziy, M.D. Caballero-Garcia, I. Perez-Garcia, E. Fernandez-Garcia and S. Wu (IAA-CSIC), A.M. Garcia Rodriguez (IAC), D. Gonzalez (GTC), C. Hernandez (GTC), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXI) and L. Piro (INAF), on behalf of a larger collaboration, report: Following the detection of GRB 251129A by SVOM/ECLAIRs (Tan et al., GCN 42877, GCN 42879), Einstein Probe (EP Team et al., GCN 42884), and by additional Swift ToO observations (Evans, GCN 42888), we observed the optical afterglow detected by Angulo et al. (GCN 42880) and further reported (Watson, GCN 42883, Wu et al., GCN 42882, Masi, GCN 42885, Li et al., GCN 42887, Lipunov et al. GCN 42892, Moskvitin et al., GCN 42897 and Guziy et al., GCN 42899), with the 10.4m GTC telescope, at the Spanish Roque de los Muchachos Observatory, on the island of La Palma, equipped with the OSIRIS+ instrument. The spectroscopic data consisted of 900s exposures using grisms R1000B and R2500I, covering the spectral range between 3,600 and 10,000 A. The observations started on Nov 29, 05:32 UT (i.e. 3.01 h after the burst trigger), and were carried out at high airmass (X~2). From a preliminary reduction, we find a highly absorbed continuum, showing several metal absorption with complex velocity structure. We interpret these lines as coming from CrII, FeII, FeII*, MgII, NiII, SiII, ZnII, all at z=1.460. The detection of iron fine structure lines links this system to the GRB. View this GCN Circular online at https://gcn.nasa.gov/circulars/42900. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40969] GRB 251129A / EP251129a: OSN and CAHA optical follow-up
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42899 SUBJECT: GRB 251129A / EP251129a: OSN and CAHA optical follow-up DATE: 25/11/29 20:25:20 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S. Guziy, A. Sota, M.D. Caballero-Garcia, R. Sanchez-Ramirez, I. Olivares, I. Perez-Garcia, E. Fernandez-Garcia, S. Wu and A.J. Castro-Tirado (IAA-CSIC), J.I. Vico Linares, A. Fernandez-Martin and J. Flores-Martin (CAHA), E. Gomez, B. Rodriguez, J.P. Lopez, N. Morant Juan, I. Castillo, A. Lozano-Fernandez, F. Lopez-Martinez, M. Salah-Martinez and R. Ardon-Leon (VIU, Valencia), M. Gritsevich (Univ. of Helsinki) and Y.-D. Hu (GXI), on behalf of a larger collaboration, report: Following the detection of GRB 251129A/EP251129a by SVOM (Tan et al. GCNC 42879) and EP (Wu et al. GCNC 42884) we imaged the gamma-ray burst error box with both the 0.9 and 1.5m telescopes at Sierra Nevada Observatory. In addition to them, we also used the 1.23m and 2.2m telescopes at the nearby Calar Alto Observatory. We clearly detect the optical afterglow discovered by Angulo et al. (GCNC 42880), also reported by Wu et al. (GCNC 42882), Masi (GCNC 42885), Li et al. (GCNC 42887), Lipunov et al. (GCNC 42892) and Moskvitin et al. (GCNC 42897). At both Sierra Nevada and Calar Alto observatories we measure R = 19.8 +/- 0.2 and i = 19.9 +/- 0.3 respectively (2.47 h and 2.90 h after the burst onset time). This preliminary photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and SDSS and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42899. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40968] GRB 251128A: AstroSat CZTI detection
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42898 SUBJECT: GRB 251128A: AstroSat CZTI detection DATE: 25/11/29 18:47:43 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> M. Tembhurnikar (IUCAA), A. Arya (IITB), A. Goyal (IITB), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short GRB 251128A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42865), Swift BAT-GUANO (DeLaunay et. al., GCN Circ. 42874), and Insight-HXMT/HE (Zhang et. al., GCN Circ. 42893). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-11-28 04:23:02 UTC. The measured peak count rate associated with the burst is 154 (+2, -2) counts/s above the background in the combined data of two quadrants (out of four), with a total of 2558 (+298, -336) counts. The local mean background count rate was 260 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 45.3 (+2.8, -2.2) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-11-28 04:23:52 UTC. The measured peak count rate associated with the burst is 509 (+72, -62) counts/s above the background in the combined data of all quadrants, with a total of 5062 (+723, -752) counts. The local mean background count rate was 1445 (+6, -5) counts/s. We measure a T90 of 47.1 (+1.9, -2.7) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42898. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40967] GRB 251129A / EP251129a: SAO RAS optical observations
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42897 SUBJECT: GRB 251129A / EP251129a: SAO RAS optical observations DATE: 25/11/29 17:59:49 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova (SAO RAS) report on behalf of GRB follow-up team. We observed the field of the SVOM GRB 251129A (Tan et al., GCN 42877) also detected by Einstein Probe as EP251129a (Wu et al., GCN 42884) and Swift (Evans, GCN 42888; Page et al., GCN 42891) with the Zeiss-1000 1m telescope of the SAO RAS on November 29, 15:27:01--16:00:22 UT (t_mid - T0 = 0.54973 days). We obtained 6 * 300 sec images in Rc band. The optical afterglow (Angulo et al., GCN 42880; Wu et al., GCN 42882; Watson, GCN 42883; Masi, GCN 42885; Li et al., GCN 42887; Lipunov et al., GCN 42892) is clearly detected in the stacked frame with the following brightness. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-29 15:27:01 0.54973 6*300 Rc 21.00 0.07 22.8 This preliminary 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/42897. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40966] GRB 251126A: SAO RAS optical observations
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42896 SUBJECT: GRB 251126A: SAO RAS optical observations DATE: 25/11/29 17:15:20 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> V. Goranskij (SAI MSU, SAO RAS), A. Moskvitin (SAO RAS), V. Shergin (SAO RAS), A. Volnova (IKI), N. Pankov (HSE, IKI), A. 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; Barthelmy et al., GCN 42876) with the Zeiss-1000 1m telescope of the SAO RAS on November 28/29 night. We obtained a series of 300 and 600 sec. images in Rc band under a good weather conditions and FWHM of about 1".8. 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; Moskvitin et al, GCN 42870; Adami et al., GCN 42871; Pankov et al., GCN 42875) is clearly detected in the stacked frame. We report preliminary brightness of the optical afterglow. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-28 22:35:56 2.2236 8*300+4*600 Rc 23.15 0.18 23.7 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/42896. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40965] GRB 251128A: GECAM-B detection
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42895 SUBJECT: GRB 251128A: GECAM-B detection DATE: 25/11/29 15:11:17 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Jia-Cong Liu, 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 251128A, at 2025-11-28T04:22:22.950 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #42865). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 46 +2/-4 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251128A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42895. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40964] GRB 251128A: SVOM/GRM observation of a long burst
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42894 SUBJECT: GRB 251128A: SVOM/GRM observation of a long burst DATE: 25/11/29 14:47:25 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM on-ground search was triggered by GRB 251128A at 2025-11-28T04:22:24.000 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42865). The GRM light curve shows that this burst consists of multiple pulses with a T90 of 47 +8/-5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251128A.png In addition, the position of this burst, as determined by Fermi/GBM (RA=117.5, Dec = 52.2, GCN #42865), is located at about 139.4 degrees from the SVOM optical axis, which is out of the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-10 to T0+45 s is best fit by a power law function. The power law index is -2.36 +0.22/-0.28. The event fluence (10-1000 keV) in this time interval is (3.08 +0.34/-0.35)E-05 erg/cm^2. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/42894. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40963] GRB 251128A: Insight-HXMT/HE detection
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42893 SUBJECT: GRB 251128A: Insight-HXMT/HE detection DATE: 25/11/29 14:43:15 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2025-11-28T04:22:22.000 (T0), Insight-HXMT/HE detected a long GRB 251128A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #42865). The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 44 +11/-18 s. The 1s peak rate, measured from T0+9.5 s, is 604 cnts/sec. Insight-HXMT/HE detected a total of 3694 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251128A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org View this GCN Circular online at https://gcn.nasa.gov/circulars/42893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40962] SVOM GRB 251129A : MASTER optical counterpart detection
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42892 SUBJECT: SVOM GRB 251129A : MASTER optical counterpart detection DATE: 25/11/29 14:26:34 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.M. Lipunov, A.Kuznetsov, I.Panchenko, E.Gorbovskoy, G.Antipov, P.Balanutsa, V.Senik, N. Tiurina, K.Zhirkov, Ya.Kechin, A.Chasovnikov, D.Vlasenko, Yu. Tselik(Lomonosov MSU, SAI, Moscow), O.A.Gress, N.M.Budnev, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D. Buckley (SAAO, South Africa), 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-Kislovodsk robotic telescope (Global MASTER-Net [1-4], http://observ.pereplet.ru) started inspect (Lipunov et al. GCN 42878) of SVOM GRB 251129A ( GCN 42877) 9 sec after notice time (997 sec after trigger time) at 2025-11-29 02:48:01 UT There is optical counterpart with unfiltered m_OT=18.7(auto-detection) at 2025-11-25 02:48:01UT, that was discovered by SVOM/COLIBRÍ (Angulo et al. GCN 42880) at 2025-11-29 02:51:22UT and also observed by SVOM/VT (Wu et al. GCN 42882, Li et al. GCN 42887), VT (Maxi et al. GCN 42885). Real time updated cover map and OT position are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3054567 [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/42892. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40961] GRB 251129A: Swift-XRT afterglow detection
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42891 SUBJECT: GRB 251129A: Swift-XRT afterglow detection DATE: 25/11/29 12:29:18 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 251129A. We searched for X-ray sources in 732 s of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 2.3 ks, obtained between T0+16.5 ks and T0+28.5 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma SVOM/ECLAIRs error region (49 arcsec) and is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 2336 s of PC mode data and 4 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 224.33074, +79.29312 which is equivalent to: RA (J2000): 14h 57m 19.38s Dec(J2000): +79d 17' 35.2" with an uncertainty of 2.1 arcsec (radius, 90% confidence). This position is 26 arcsec from the SVOM/ECLAIRs position. The position is consistent with the optical afterglow (GCNs 42880, 42882, 42883, 42885, 42887) and the EP X-ray transient (GCN 42884). The light curve can be modelled can be modelled with a power-law decay with a decay index of alpha=6.23 (+0.32, -0.29). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.71 (+0.22, -0.20). The best-fitting absorption column is 7.3 (+3.7, -3.3) x 10^20 cm^-2, in excess of the Galactic value of 2.9 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 2.6 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.3 (+3.7, -3.3) x 10^20 cm^-2 Galactic foreground: 2.9 x 10^20 cm^-2 Excess significance: 2.2 sigma Photon index: 2.71 (+0.22, -0.20) If the light curve continues to decay with a power-law decay index of 6.2, the count rate at T+24 hours will be 1.1 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-15 (4.2 x 10^-15) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/00021892. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021892. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42891. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40960] The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42890 SUBJECT: The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster DATE: 25/11/29 11:57:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Wu, H. C. Ding (AHNU), Y. Wu, Y. H. Jiang, C. Y. Dai (NJU), Y. Wang (PMO), W. J. Zhang, Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709248941 at 2025-11-29T11:07:16 is associated with the known source Perseus Cluster. 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/42890. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40959] Swift trigger 1418333 is not an astrophysical source
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42889 SUBJECT: Swift trigger 1418333 is not an astrophysical source DATE: 25/11/29 11:24:27 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team: Trigger 1418333 was caused by particles in the South Atlantic Anomaly, and is not an interesting, astrophysical event. View this GCN Circular online at https://gcn.nasa.gov/circulars/42889. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40958] GRB 251129A: Swift ToO observations
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42888 SUBJECT: GRB 251129A: Swift ToO observations DATE: 25/11/29 07:05:48 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event GRB 251129A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021892 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42888. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40957] GRB 251129A: SVOM/VT optical fading
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42887 SUBJECT: GRB 251129A: SVOM/VT optical fading DATE: 25/11/29 05:41:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li , L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), W. J. Tan (IHEP), D. F. Kong (GXU) report on behalf of the SVOM/VT team. SVOM/VT performed an automatic slew to the field of GRB 251129A (sb25112901, Tan et al., GCN 42879). The observation stared at 2025-11-29T02:43:03 UTC, I.e., 658 seconds post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With the downloaded early X band data, the optical counterpart (Angulo et al. GCN 42880; Watson, GCN 42883; Wu et al., GCN 42882; Masi et al. GCN 42885) was clearly detected in both channels. The measurements are given below: Mid_time Band Exposure Time Magnitude (AB) 12.43 min VT_B 50 sec 18.16+/-0.03 mag 12.43 min VT_R 50 sec 17.89+/-0.03 mag 44.96 min VT_B 50 sec 19.11+/-0.04 mag 44.96 min VT_R 50 sec 18.80+/-0.03 mag It was fading with a slope of about 0.7 with a single power law. Our photometry was not corrected for Galactic extinction. 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/42887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40956] EP251129a: Global MASTER-Net observations report
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42886 SUBJECT: EP251129a: Global MASTER-Net observations report DATE: 25/11/29 05:36:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251129a ( EP Team et al., GCN 42884) errorbox 107 sec after trigger time at 2025-11-29 03:16:10 UT, with upper limit up to 17.6 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -11.4 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=3054702 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 167 | 2025-11-29 03:16:10 | MASTER-Kislovodsk | (14h 59m 24.03s , +79d 38m 56.6s) | C | 120 | 17.2 | 287 | 2025-11-29 03:16:10 | MASTER-Kislovodsk | (14h 59m 24.03s , +79d 38m 56.6s) | C | 360 | 17.6 | Coadd 167 | 2025-11-29 03:16:10 | MASTER-Kislovodsk | (15h 21m 34.38s , +79d 11m 04.2s) | C | 120 | 17.4 | 307 | 2025-11-29 03:18:30 | MASTER-Kislovodsk | (14h 59m 22.72s , +79d 39m 05.4s) | C | 120 | 17.0 | 307 | 2025-11-29 03:18:30 | MASTER-Kislovodsk | (15h 21m 33.89s , +79d 11m 14.4s) | C | 120 | 17.1 | 447 | 2025-11-29 03:20:49 | MASTER-Kislovodsk | (14h 59m 21.42s , +79d 39m 14.1s) | C | 120 | 16.6 | 447 | 2025-11-29 03:20:49 | MASTER-Kislovodsk | (15h 21m 32.90s , +79d 11m 24.4s) | C | 120 | 16.7 | 587 | 2025-11-29 03:23:09 | MASTER-Kislovodsk | (14h 59m 20.23s , +79d 39m 22.9s) | C | 120 | 16.4 | 707 | 2025-11-29 03:23:09 | MASTER-Kislovodsk | (14h 59m 20.29s , +79d 39m 22.8s) | C | 360 | 17.0 | Coadd 587 | 2025-11-29 03:23:09 | MASTER-Kislovodsk | (15h 21m 29.63s , +79d 11m 35.4s) | C | 120 | 14.6 | 727 | 2025-11-29 03:25:29 | MASTER-Kislovodsk | (14h 59m 19.13s , +79d 39m 30.8s) | C | 120 | 16.3 | 867 | 2025-11-29 03:27:49 | MASTER-Kislovodsk | (14h 59m 17.67s , +79d 39m 36.8s) | C | 120 | 16.1 | 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/42886. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40955] GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
by GCN Circulars 29 Nov '25

29 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42885 SUBJECT: GRB 251129A: Optical Observations via Virtual Telescope Project, Italy DATE: 25/11/29 05:27:43 GMT FROM: Gianluca Masi at Virtual Telescope Project <gianluca(a)bellatrixobservatory.org> Gianluca Masi, Virtual Telescope Project (Italy), reports: We attempted to observe the optical counterpart of GRB 251129A (Wenjun et al., GCN 42877) with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera, its QE peaking (90%) in the red part of the spectrum. We collected five, 300-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 29 Nov., 04:54:23 UTC, that is about 2.4 hours after the burst. We detected a bright object at the following position (J2000.0): R.A.: 14 57 18.81 Decl.: +79 17 34.6 mean residuals < 0.1” on both axes R= 19.5 (assuming R-mags from Gaia DR2 for the reference stars). This position is consistent with Angulo et al. (GCN 42880). The source is not present in the PanSTARRS DR1 dataset. View this GCN Circular online at https://gcn.nasa.gov/circulars/42885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40954] 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 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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