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

[vsnet-grb-info 41094] GRB 251203C: Swift/UVOT Upper Limit
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43014 SUBJECT: GRB 251203C: Swift/UVOT Upper Limit DATE: 25/12/06 18:22:42 GMT FROM: N. Klingler at NASA-GSFC/UMBC/CRESST II <noelklingler(a)gmail.com> Swift/UVOT has performed follow-up observations of the field of GRB 251203C, starting 20.3 ks after the SVOM trigger sb25120305 (Brunet et al; GCN Circ. 42976). No source is detected at the position of the optical counterpart (R.A., Dec. = 51.701538, -7.382688) reported by Li et al. (GCN Circ. 42987) and Turpin et al. (GCN Circ. 42988). 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(AB) u 20269 20514 241 >20.69 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.046 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43014. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41093] Konus-Wind detection of GRB 251118A
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43013 SUBJECT: Konus-Wind detection of GRB 251118A DATE: 25/12/06 16:38:47 GMT FROM: Valentina Panteleeva at Ioffe Institute <panteleevav228(a)gmail.com> V. Panteleeva, D. Frederiks, A. Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 251118A (Fermi-GBM detection: The Fermi GBM team, GCN 42743; Palafox and Meegan, GCN 42783; BALROG localization: Preis and Greiner, GCN 42745; Fermi-LAT detection: Gupta and Khalil, GCN 42752; GECAM-B detection: Ren et al., GCN 42779; Glowbug detection: Cheung et al., GCN 42784) triggered Konus-Wind at T0=73904.449 s UT (20:31:44.449). The burst light curve starts, at ~T0-20.5 s, with a short soft initial pulse (precursor) which had a duration of about 25.8 s. The precursor is followed, starting at ~T0+32 s, by the main episode, lasting for ~25 s. The total duration of the burst is ~48 s. The emission in the main episode is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251118_T73904/ As observed by Konus-Wind, the burst had the total fluence of 1.07(-0.03,+0.03)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+35.776 s, of 2.03(-0.15,+0.15)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the initial pulse (measured from T0 to T0+8.448 s) is best described in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.94(-0.03,+0.12) and Ep < 41 keV (chi2 = 89/85 dof). Fitting this spectrum by a GRB (Band) model results in the same estimates of alpha and Ep, and gives only an upper limit on the high energy photon index beta of -2.8 (chi2 = 89/84 dof). The time-averaged spectrum of the main episode (measured from T0+33.024 to T0+65.536 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.29(-0.03,+0.04), the high energy photon index beta = -2.56(-0.08,+0.07), the peak energy Ep = 154(-5,+5) keV (chi2 = 110/97 dof). The spectrum near the maximum count rate (measured from T0+33.024 to T0+36.608 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.74(-0.05,+0.06), the high energy photon index beta = -2.53(-0.10,+0.08), the peak energy Ep = 251(-12,+12) keV (chi2 = 68/69 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/43013. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41092] GRB 251205A: Zeiss-1000 Koshka observatory optical observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43012 SUBJECT: GRB 251205A: Zeiss-1000 Koshka observatory optical observations DATE: 25/12/06 14:44:43 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE,IKI), A. Novichonok (Petrozavodsk State University, KIAM), S. Schmalz (KIAM), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed the optical afterglow of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008; Malesani et al., GCN 43009; O'Neill et al., GCN 43010) using the Zeiss-1000 telescope at Koshka observatory (INASAN). The observations started/ended on 2025-12-06 (UT) 00:57:28/04:07:07. Preliminary photometry of the initial stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-12-06 00:57:28 0.05747 10*90 R 17.92 0.06 20.5 The photometry is based on nearby USNO-B1.0 stars and not corrected for Galaxy extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41091] GRB 251205A: Zeiss-1000 Koshka observatory optical observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43012 SUBJECT: GRB 251205A: Zeiss-1000 Koshka observatory optical observations DATE: 25/12/06 14:44:43 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE,IKI), A. Novichonok (Petrozavodsk State University, KIAM), S. Schmalz (KIAM), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed the optical afterglow of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008; Malesani et al., GCN 43009; O'Neill et al., GCN 43010) using the Zeiss-1000 telescope at Koshka observatory (INASAN). The observations started/ended on 2025-12-06 (UT) 00:57:28/04:07:07. Preliminary photometry of the initial stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-12-06 00:57:28 0.05747 10*90 R 17.92 0.06 20.5 The photometry is based on nearby USNO-B1.0 stars and not corrected for Galaxy extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41090] GRB 251205A: Zeiss-1000 Koshka observatory optical observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43012 SUBJECT: GRB 251205A: Zeiss-1000 Koshka observatory optical observations DATE: 25/12/06 14:44:43 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE,IKI), A. Novichonok (Petrozavodsk State University, KIAM), S. Schmalz (KIAM), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed the optical afterglow of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008; Malesani et al., GCN 43009; O'Neill et al., GCN 43010) using the Zeiss-1000 telescope at Koshka observatory (INASAN). The observations started/ended on 2025-12-06 (UT) 00:57:28/04:07:07. Preliminary photometry of the initial stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-12-06 00:57:28 0.05747 10*90 R 17.92 0.06 20.5 The photometry is based on nearby USNO-B1.0 stars and not corrected for Galaxy extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41089] GRB 251205A: COLIBRÍ optical observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43011 SUBJECT: GRB 251205A: COLIBRÍ optical observations DATE: 25/12/06 12:07:07 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the Swift GRB 251205A (S. Lanava et al., GCN Circ. 43005) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-12-06 10:04:31 to 10:47:46 UTC (from 10.41 to 11.13 hours after the trigger) and obtained 32 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 S. Lanava et al. (GCN Circ. 43005); V. M. Lipunov et al. (GCN Circ. 43006); A. de Ugarte Postigo et al. (GCN Circ. 43008); D. B. Malesani et al. (GCN Circ. 43009) and D. O’Neill et al. (GCN Circ. 43010), at a preliminary magnitude of: r = 18.26 +/- 0.03 z = 17.97 +/- 0.02 Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43011. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41088] GRB 251205A: GOTO optical afterglow detection
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43010 SUBJECT: GRB 251205A: GOTO optical afterglow detection DATE: 25/12/06 11:03:38 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, G. Ramsay, A. Kumar, B. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, S. Belkin, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien,, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, D. Pollacco, J. Casares Vel'azquez, T. Killestein, B. Godson 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 251205A. Serendipitous observations from the all-sky survey covered the position of the counterpart (Malesani et al., GCN 43009; Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008) at 2025-12-06 06:12:01 UT, (+6.5h post trigger). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. The counterpart was detected in the GOTO L-band (400-700nm) mag = 18.16 ± 0.12 (AB). 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/43010. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41087] GRB 251205A: NOT optical observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43009 SUBJECT: GRB 251205A: NOT optical observations DATE: 25/12/06 09:45:00 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. K. Aris-Kiss (Helsinki), M. Korp-Lagg (Aalto University), S. Wedemeyer (Oslo), S. Armas Perez (NOT) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008) using the Nordic Optical Telescope (NOT) equipped with the StanCam camera. Observations started on 2025-12-06 at 05:25:33 UT (5.75 hr after the trigger). Five 150 s observations were taken using the StanCam “interference i” filter. The optical afterglow is well detected in single images. At a mean time of 5.90 hr after the trigger, we measure a magnitude i = 17.93 +- 0.03. This magnitude is in the AB system and is not corrected for Galactic extinction. We note that, due to the small field-of-view of StanCam, only one star from the Pan-STARRS catalog could be used for photometric calibration. Considering that the StanCam i filter is (slightly) different from the Pan-STARRS one, an extra systematic error of 0.1 mag should be conservatively added to the photometric error budget. View this GCN Circular online at https://gcn.nasa.gov/circulars/43009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41086] GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43008 SUBJECT: GRB 251205A: GTC/OSIRIS+ redshift z = 1.100 DATE: 25/12/06 09:08:39 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. de Ugarte Postigo (LAM), S. Geier (GTC), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), L. Izzo (INAF/OACN and DARK/NBI), J. F. Agui Fernandez (CAHA), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), D. Perez Valladares (GTC) report: We observed the optical counterpart of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In the 30-s acquisition image (beginning on 2025-12-06 at 05:21:34 UT, that is 5.68 hr after trigger), the optical afterglow is well detected with a magnitude i = 17.78 +- 0.03 AB, calibrated against nearby Pan-STARRS objects, and not corrected for Galactic extinction. We also report the following, improved coordinates (0.3" accuracy): RA(J2000) = 13:21:05.32 Dec(J2000) = +29:55:43.6 A total of 4 spectra by 900 s were secured, starting on 2025-12-06 at 05:31:22 UT (5.86 hr after trigger), using grism R1000B. Continuum is detected over the range 3750-7750 AA. A number of absorption features are detected, which we interpret as due to Fe II 2344, 2383, 2586, 2600, Mg II 2796, 2803, and Mg I 2852, all at a common redshift z = 1.100, which we suggest to be the redshift of GRB 251205A. Given the redshift value measured in absorption, it is thus unlikely that the GRB is associated with the nearby, bright galaxy with photometric redshift z = 0.25 noted by Lipunov et al. (GCN 43006). View this GCN Circular online at https://gcn.nasa.gov/circulars/43008. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41085] GRB 251205A: Enhanced Swift-XRT position
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43007 SUBJECT: GRB 251205A: Enhanced Swift-XRT position DATE: 25/12/06 03:12:58 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 366 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251205A, 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 = 200.27190, +29.92894 which is equivalent to: RA (J2000): 13h 21m 05.26s Dec (J2000): +29d 55' 44.2" with an uncertainty of 2.4 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/43007. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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