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

[vsnet-grb-info 40124] GRB 251001B: COLIBRÍ optical observations
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42054 SUBJECT: GRB 251001B: COLIBRÍ optical observations DATE: 25/10/02 10:03:11 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Camila Angulo (UNAM), Rosa L. Becerra (U Roma), Antonio de Ugarte Postigo (LAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (OCA), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Fredd Sánchez Álvarez (UNAM): We imaged the field of the GRB 251001B (Fermi GBM team, GCN Circ. 42038; Beardmore et al. GCN Circ. 42039) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-02T06:13:31 to 08:49:34 UTC (from 15.94 to 18.54 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart previously reported by Gompertz et al. GCN Circ. 42040; An et al. GCN Circ. 42041; Strausbaugh & Cucchiara GCN Circ. 42043; O'Neill et al. GCN Circ. 42046; A. de Ugarte Postigo et al., GCN Circ. 42050; Ma et al., GCN Circ. 42051 and Sanchez-Ramirez et al., GCN 42053 at preliminary magnitudes of: r = 21.56 +/- 0.06 z = 21.28 +/- 0.13 Our measured r-band magnitude is consistent with the magnitude reported by the NOT (Ugarte Postigo et al., GCN Circ. 42050), indicating a possible flattening in the optical afterglow. Further observations and analysis are ongoing in g, r, i, z and y filters. 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/42054. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40123] GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42053 SUBJECT: GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162 DATE: 25/10/02 09:33:41 GMT FROM: Ruben Sanchez-Ramirez at IAA-CSIC <ruben(a)iaa.es> R. Sanchez-Ramirez (IAA-CSIC), Y.-D. Hu (GXI), A. J. Castro-Tirado, S. Guziy, M.D. Caballero-Garcia, S.-Y. Wu and I. Perez-Garcia (IAA-CSIC), R. Scarpa (GTC, IAC), D. Gonzalez (GTC), A. Cabrera-Lavers (GTC, IAC), S. B. Pandey (ARIES), M. Gritsevich (Univ. of Helsinki), J. Becerra-Gonzalez (IAC), L. Piro (INAF/IAPS) and B.-B. Zhang (NJU), on behalf of a larger collaboration, report: Following the detection of GRB 251001B by Fermi (Fermi Team, GCN 42038, Neights et al. GCN 42047) and Swift (Beardmore et al. GCN 42039), we observed the optical afterglow (Gompertz et al. GCN 42040, An et al. GCN 42041, Strausbaugh et al. GCN 42043, O'Neill et al. GCN 42046, de Ugarte Postigo et al., GCN 42050, Ma et al., GCN 42051) 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 observations were performed at high airmass and consisted of 3x900s exposures using grism R1000B, with a spectral coverage between 3,600 and 7,700 A (R~600). The observations started on Oct 2, 02:39 UT (i.e. 12.35 h after the burst trigger). From a preliminary reduction, we find a strong DLA at ~4000A, as well as several metal absorption lines that we interpret as coming from NV, SiII, SiII*, OI, CII, SiIV, CIV, FeII, FeII*, AlII, AlIII, ZnII, CrII, all at z=2.162. The detection of SiII* and FeII* links this system to the GRB. We also note the presence of Lya in emission at the same redshift. View this GCN Circular online at https://gcn.nasa.gov/circulars/42053. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40122] GRB 251001B: Swift-XRT refined Analysis
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42052 SUBJECT: GRB 251001B: Swift-XRT refined Analysis DATE: 25/10/02 07:52:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.8 ks of XRT data for GRB 251001B, from 99 s to 40.1 ks after the trigger. The data comprise 540 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=1.34 (+/-0.06). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.92 (+0.08, -0.07). The best-fitting absorption column is 8.8 (+2.0, -1.9) x 10^20 cm^-2, in excess of the Galactic value of 2.6 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.74 (+0.19, -0.18) and a best-fitting absorption column of 8.6 (+5.7, -4.8) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.6 (+5.7, -4.8) x 10^20 cm^-2 Galactic foreground: 2.6 x 10^20 cm^-2 Excess significance: 2.1 sigma Photon index: 1.74 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 1.34, the count rate at T+24 hours will be 9.6 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x 10^-14 (4.3 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01400467. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42052. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40121] GRB 251001B: SVOM/VT optical observation
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42051 SUBJECT: GRB 251001B: SVOM/VT optical observation DATE: 25/10/02 07:32:26 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Z. H. Yao, Y. L. Qiu, C. Wu, H. L. Li, 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/VT performed a Target of Opportunity observation of GRB 251001B detected by Fermi/GBM and Swift/BAT (Fermi GBM team, GCN 42038; Beardmore et al., GCN 42039; Beardmore et al., GCN 42045; Neights & Meegan, GCN 42047). SVOM/VT began observing the field at 2025-10-01T15:03:04 UTC, 0.762 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 (Gompertz et al., GCN 42040; An et al., GCN 42041; Strausbaugh & Cucchiara, GCN 42043; O'Neill et al., GCN 42046; Lipunov et al., GCN 42048; de Ugarte Postigo et al., GCN 42050) was clearly detected in both VT_B and VT_R bands. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 3.790 | 38*70 | VT_B | 22.06 | 0.09 3.819 | 35*70 | VT_R | 21.31 | 0.07 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/42051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40120] GRB 251001B: NOT optical observations
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42050 SUBJECT: GRB 251001B: NOT optical observations DATE: 25/10/02 07:25:01 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), B. Schneider (LAM), B. P. Gompertz (Birmingham), A. Martin-Carrillo (UCD) and J. Maiz Apellaniz (IAA-CSIC) report: We observed the field of GRB 251001B (Fermi GBM team, GCN 42038; Beardmore et al. GCN 42039) using the 2.5 m Nordic Optical Telescope (NOT) equipped with ALFOSC. Observations started on 2 October 2025 at 02:37:23 UT (12.33 hr after the trigger) and consisted of 3x300 s and 5x200 s in the SDSS r and z bands, respectively. The combined images reveal the presence of the afterglow identified by Gompertz et al. (GCN 42040; An et al. GCN 42041; Strausbaugh & Cucchiara GCN 42043; O'Neill et al. GCN 42046) at a magnitude of r = 21.54 +/- 0.06 (AB) calibrated against field stars of the Pan-STARRS catalogue and not corrected by Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42050. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40119] GRB 251001C: Glowbug gamma-ray detection
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42049 SUBJECT: GRB 251001C: Glowbug gamma-ray detection DATE: 25/10/02 01:49:29 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 251001C, which was also detected by CALET (Trigger 1443366004). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-01 15:07:24.688 with a duration of 11.0 s and a total significance of about 27.2 sigma. The light curve comprises a bright peak at ~T0+1s followed a faint peak at ~T0+7s. The best-fit localization is RA, Decl. (J2000, deg) = 82.7, 21.9 with a radius of 10.0 deg (95% confidence), with a highly uncertain systematic uncertainty. 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 recently 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/42049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40118] Swift GRB 251001B: Global MASTER-Net observations report
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42048 SUBJECT: Swift GRB 251001B: Global MASTER-Net observations report DATE: 25/10/02 00:16:59 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 251001B ( A. P. Beardmore et al., GCN 42039) errorbox 34585 sec after notice time and 35427 sec after trigger time at 2025-10-02 00:07:47 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 67 deg. The sun altitude is -32.7 deg. The galactic latitude b = -62 deg., longitude l = 211 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3004463 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 35517 | MASTER-Kislovodsk | C | 180 | 18.4 | 35517 | MASTER-Kislovodsk | C | 180 | 18.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40117] GRB 251001B: Fermi GBM Observation
by GCN Circulars 01 Oct '25

01 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42047 SUBJECT: GRB 251001B: Fermi GBM Observation DATE: 25/10/01 21:33:18 GMT FROM: eliza.neights(a)gmail.com Eliza Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:17:19.05 UT on 01 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251001B (trigger 781021044/251001595) which was also detected by Swift BAT (A. P. Beardmore et al. 2025, GCN 42039). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 53 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.7 to T0+16.7 s is best fit by a Comptonized function with index 0.22 +/- 0.03 and peak energy 107 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.7 s in the 10-1000 keV band is 1.4 +/- 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/42047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40116] GRB 251001B: Further GOTO observations of optical counterpart.
by GCN Circulars 01 Oct '25

01 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42046 SUBJECT: GRB 251001B: Further GOTO observations of optical counterpart. DATE: 25/10/01 20:34:36 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, B. P. Gompertz, G. Ramsay, R. Starling, M. Kennedy, B. Godson, J. Lyman, K. Ackley, M. J. Dyer, K. Ulaczyk, A. Kumar,, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on new observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 251001B (Fermi GBM team, GCN 42038; Beardmore et al. GCN 42039). Following the detection of the optical counterpart of GRB 251001B (Gompertz et al. GCN 42040, An et al. GCN 42041, Strausbaugh & Cucchiara, GCN 42043) we detect the counterpart again in an additional epoch of GOTO L-band (400-700 nm) imaging taken at 2025-10-01 15:44:25 UT (1.45h post-trigger) consisting of 4x90s exposures. We find the counterpart has faded to L=20.6±0.3 AB mag, consistent with a power law decay with index: alpha = -0.75. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are 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 and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/42046. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40115] GRB 251001B: Enhanced Swift-XRT position
by GCN Circulars 01 Oct '25

01 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42045 SUBJECT: GRB 251001B: Enhanced Swift-XRT position DATE: 25/10/01 18:10:10 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 700 s of XRT Photon Counting mode data and 2 UVOT images for GRB 251001B, 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 = 42.65089, -23.02048 which is equivalent to: RA (J2000): 02h 50m 36.21s Dec (J2000): -23d 01' 13.7" with an uncertainty of 2.1 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://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/42045. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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