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

[vsnet-grb-info 41134] GRB 251208A: GECAM-B observation of a short burst
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43054 SUBJECT: GRB 251208A: GECAM-B observation of a short burst DATE: 25/12/09 16:15:06 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 251208A, at 2025-12-08T09:25:57.550 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43027) and SVOM/GRM (Yue Wang et al., GCN #43042). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 2.4 +0.7/-1.2 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251208A.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/43054. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41133] Fermi GRB 251209A: Global MASTER-Net observations report
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43053 SUBJECT: Fermi GRB 251209A: Global MASTER-Net observations report DATE: 25/12/09 15:30:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251209A ( Fermi GBM team, GCN 43048) errorbox 4838 sec after notice time and 4882 sec after trigger time at 2025-12-09 14:45:26 UT, with upper limit up to 15.1 mag. Observations started at twilight. The observations began at zenith distance = 80 deg. The sun altitude is -12.3 deg. The galactic latitude b = 66 deg., longitude l = 80 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3065758 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4912 | 2025-12-09 14:45:26 | MASTER-Kislovodsk | (14h 17m 04.16s , +45d 00m 13.7s) | C | 60 | 15.1 | 4912 | 2025-12-09 14:45:26 | MASTER-Kislovodsk | (14h 22m 26.41s , +44d 40m 31.0s) | 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/43053. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41132] Fermi GRB 251208C: Global MASTER-Net observations report
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43052 SUBJECT: Fermi GRB 251208C: Global MASTER-Net observations report DATE: 25/12/09 15:30:32 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 251208C ( Fermi GBM team, GCN 43030) errorbox 1 days 6304 sec after notice time and 1 days 6326 sec after trigger time at 2025-12-09 14:37:58 UT, with upper limit up to 15.6 mag. Observations started at twilight. The observations began at zenith distance = 77 deg. The sun altitude is -11.0 deg. The galactic latitude b = -39 deg., longitude l = 14 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3064550 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 92816 | 2025-12-09 14:37:58 | MASTER-Kislovodsk | (20h 51m 14.16s , -30d 11m 05.4s) | C | 180 | 12.8 | 93444 | 2025-12-09 14:49:26 | MASTER-Kislovodsk | (20h 51m 12.38s , -29d 02m 48.7s) | C | 60 | 13.6 | 93444 | 2025-12-09 14:49:26 | MASTER-Kislovodsk | (20h 46m 31.77s , -28d 42m 11.8s) | C | 60 | 14.3 | 93525 | 2025-12-09 14:50:47 | MASTER-Kislovodsk | (21h 01m 36.94s , -30d 57m 36.2s) | C | 60 | 12.5 | 93525 | 2025-12-09 14:50:47 | MASTER-Kislovodsk | (20h 56m 51.84s , -30d 36m 58.9s) | C | 60 | 13.2 | 93604 | 2025-12-09 14:52:07 | MASTER-Kislovodsk | (20h 56m 03.09s , -27d 10m 45.4s) | C | 60 | 14.7 | 93604 | 2025-12-09 14:52:07 | MASTER-Kislovodsk | (20h 51m 26.46s , -26d 50m 06.8s) | C | 60 | 15.1 | 93684 | 2025-12-09 14:53:27 | MASTER-Kislovodsk | (21h 00m 18.16s , -28d 43m 43.1s) | C | 60 | 14.0 | 93684 | 2025-12-09 14:53:27 | MASTER-Kislovodsk | (21h 04m 59.03s , -29d 04m 22.4s) | C | 60 | 13.9 | 93765 | 2025-12-09 14:54:47 | MASTER-Kislovodsk | (20h 38m 01.33s , -26d 48m 57.8s) | C | 60 | 14.5 | 93765 | 2025-12-09 14:54:47 | MASTER-Kislovodsk | (20h 42m 37.44s , -27d 09m 35.3s) | C | 60 | 14.1 | 93845 | 2025-12-09 14:56:07 | MASTER-Kislovodsk | (20h 32m 54.99s , -28d 43m 10.7s) | C | 60 | 13.1 | 93845 | 2025-12-09 14:56:07 | MASTER-Kislovodsk | (20h 37m 34.74s , -29d 03m 45.7s) | C | 60 | 12.5 | 93925 | 2025-12-09 14:57:27 | MASTER-Kislovodsk | (20h 48m 49.10s , -25d 15m 12.4s) | C | 60 | 14.9 | 93925 | 2025-12-09 14:57:27 | MASTER-Kislovodsk | (20h 44m 16.39s , -24d 54m 32.9s) | C | 60 | 15.3 | 94005 | 2025-12-09 14:58:47 | MASTER-Kislovodsk | (21h 02m 06.24s , -25d 16m 49.4s) | C | 60 | 15.1 | 94005 | 2025-12-09 14:58:47 | MASTER-Kislovodsk | (20h 57m 32.94s , -24d 56m 08.5s) | C | 60 | 15.6 | 94085 | 2025-12-09 15:00:07 | MASTER-Kislovodsk | (21h 09m 35.36s , -27d 08m 43.7s) | C | 60 | 14.6 | 94085 | 2025-12-09 15:00:07 | MASTER-Kislovodsk | (21h 04m 58.34s , -26d 48m 02.7s) | C | 60 | 14.9 | 94697 | 2025-12-09 15:10:19 | MASTER-Kislovodsk | (21h 10m 53.04s , -30d 37m 42.3s) | C | 60 | 12.2 | 94857 | 2025-12-09 15:12:59 | MASTER-Kislovodsk | (20h 35m 32.24s , -25d 17m 04.5s) | C | 60 | 13.9 | 94947 | 2025-12-09 15:14:29 | MASTER-Kislovodsk | (21h 18m 27.36s , -29d 04m 37.5s) | C | 60 | 13.4 | 94947 | 2025-12-09 15:14:29 | MASTER-Kislovodsk | (21h 13m 59.27s , -28d 44m 11.1s) | C | 60 | 13.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43052. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41131] GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43051 SUBJECT: GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/12/09 14:48:58 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Jean-Luc Atteia (IRAP), Noémie Globus (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Marius Brunet (IRAP) report: We imaged the field of the SVOM GRB 251206A (Brunet et al., GCN Circ. 43031) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-12-09 04:39 to 0625 UTC (from 55.8 to 57.2 hours after the trigger) and obtained 80 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, and analyzed with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source inside the ECLAIRs uncertainty region (Brunet et al., GCN Circ. 43031) to the following 5-sigma limits: r > 23.3 z > 22.3 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/43051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41130] GRB 251208B: Swift-XRT afterglow detection
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43050 SUBJECT: GRB 251208B: Swift-XRT afterglow detection DATE: 25/12/09 13:53:09 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.A. Kennea (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Lanava (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the GUANO (DeLaunay et al. GCN 43033) and Fermi/LAT-detected (Bissaldi et al. GCN 43034) burst GRB 251208B. We searched for X-ray sources in 4.8 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 4.8 ks, obtained between T0+33.1 ks and T0+45.4 ks. Three uncatalogued X-ray sources are detected within the estimated 3-sigma Fermi/LAT error region (414 arcsec), of which one ("Source 1") is 2.9 sigma above the RASS limit and it is fading with 2.2 sigma significance and thus is believed to be the GRB afterglow. Using 4576 s of PC mode data and 5 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 = 228.48108, +29.04575 which is equivalent to: RA (J2000): 15h 13m 55.46s Dec(J2000): +29d 02' 44.7" with an uncertainty of 2.3 arcsec (radius, 90% confidence). This position is 87 arcsec from the Fermi/LAT position. The light curve is consistent with a constant source of mean count rate 5.0e-02 ct/sec. A power-law fit gives an index of 1.2 (+/-1.2). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+0.4, -0.3). The best-fitting absorption column is 1.4 (+1.1, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 2.6 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 3.1 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+1.1, -0.8) x 10^21 cm^-2 Galactic foreground: 2.6 x 10^20 cm^-2 Excess significance: 2.3 sigma Photon index: 2.2 (+0.4, -0.3) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/00021893. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021893. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43050. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41129] GRB 251208D: LAST optical upper limit
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43049 SUBJECT: GRB 251208D: LAST optical upper limit DATE: 25/12/09 13:50:40 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 251208D, detected by SVOM (Lin et al., GCN 43032). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). We observed the field of GRB 251208D using 4 divergent telescopes (each with a 7.4 deg^2 FoV) in clear band (similar to the Gaia Bp band) over 5 sequential epochs. Each epoch consists of 20x20s exposures. We began observations at 2025-12-08 17:22:15 UTC (T-T0 = 0.53h). We coadd a total of 100x20s exposure images and perform image subtraction using a reference image of the field. We do not detect any new optical source up to a limiting magnitude of 20.33 (AB) within the error region reported in Lin et al., GCN 43032. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41128] GRB 251209A: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43048 SUBJECT: GRB 251209A: Fermi GBM Final Real-time Localization DATE: 25/12/09 13:34:44 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 13:24:03 UT on 9 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251209A (trigger 786979448.987734 / 251209558). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 214.2, Dec = 43.1 (J2000 degrees, equivalent to J2000 14h 16m, 43d 06'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 52.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41127] GRB 251208D: LCO analysis of the XRT sources
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43047 SUBJECT: GRB 251208D: LCO analysis of the XRT sources DATE: 25/12/09 12:07:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. B. Malesani (DAWN/NBI and Radboud), D. Turpin, A. Saccardi (CEA/Irfu), Z.-Y. Lin, F. Cangemi (APC), report on behalf of the SVOM mission team: Following the report of two X-ray sources detected by Swift/XRT (Evans et al., GCN 43043), we inspected again our images taken with LCO (Turpin et al., GCN 43037) of the field of the SVOM GRB 251208A (Lin et al., GCN 43032). * XRT source #1 matches the high proper-motion star TYC 5226-156-1 (distance ~500 pc). We measure a magnitude of r = 11.34 +- 0.02, consistent with the APASS archival value r = 11.34 +- 0.06. * XRT source #2 is consistent with SDSS J223038.66-003108.3, a known QSO at z = 1.32 with magnitude r = 20.34 (from SDSS) and r = 20.65 (from Pan-STARRS), possibly indicating some long-term variability. We measure r = 20.73 +- 0.12, indicating that the object is not in a particularly active state. Our observations suggest that neither sources are likely related to the high-energy emission observed by SVOM. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41126] GRB 251208B: Fermi GBM Observation
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43046 SUBJECT: GRB 251208B: Fermi GBM Observation DATE: 25/12/09 11:51:58 GMT FROM: Andreas von Kienlin at MPE <azk(a)mpe.mpg.de> A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 10:17:17.29 UT on 08 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251208B (trigger 786881842/251208429). which was also detected by Fermi-LAT (E. Bissaldi et al. 2025, GCN 43034) and Swift/BAT-GUANO (GCN #43033). The Fermi GBM on-ground location was reported by the Fermi-GBM team in GCN 43028 and is consistent with the Fermi-LAT and Swift/BAT positions. The GBM light curve shows a structured emission episode with a duration (T90) of about 62.5 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+61.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.67 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 250 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (9.5 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+55 s in the 10-1000 keV band is 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/43046. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41125] GRB 251208B: GROWTH-India Telescope optical upper limits
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43045 SUBJECT: GRB 251208B: GROWTH-India Telescope optical upper limits DATE: 25/12/09 09:02:28 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> A. Kumar, T. Mohan, V.Swain, S. Patil, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of Fermi GBM transient (Fermi GBM Team, GCN 43028), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-12-08T23:43:57 UT, i.e., about 13.4 hours after the Fermi GBM Trigger. Exposures were obtained in r' and i' filters. We did not detect any transient in our images within the Fermi-LAT on-ground localization region (Bissaldi et al., GCN 43034). Additionally, we checked the source 1 and 5 of Swift-XRT ToO observations (Evans at al., GCN 43035), and did not detect any optical counterpart at their respective position and uncertainty. The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (hrs) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | ------------- | ------------------- | ---------------- | | 61018.007928 | r' | 13.90 | 3 x 360 | 20.6 | | 61018.020746 | i' | 14.21 | 2 x 360 | 17.4 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43045. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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