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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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