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

[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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[vsnet-grb-info 41084] Swift GRB 251205A : MASTER OT detection with host galaxy
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43006 SUBJECT: Swift GRB 251205A : MASTER OT detection with host galaxy DATE: 25/12/06 01:42:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.M. Lipunov (Lomonosov MSU), V.Senik, E.Gorbovskoy, A.Kuznetsov, I.Panchenko, G.Antipov, P.Balanutsa, K.Zhirkov, N. Tiurina, 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 JuanUni.,Argentina); D.Buckley (SAAO), 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 of MASTER Global Robotic Net (Lipunov et al. [1-4], http://observ.pereplet.ru ), started Swift GRB 251205A (Lanava et al GCN 43005) error-box observations in alert mode (PP filters) 19s after notice time at at 2025-12-05 23:41:19 UT, Lipunov et al. GCN 43004 MASTER auto-detection system found optical counterpart MASTER OT J132105.37+295545.8 , first publishied by Swift (GCN 43005) with unfiltered m_OT~18.1m We have also prompt wide-field cameras images, the reduction will be later. There is host(possible) galaxy in 4.36" from GRB counterpart with z_phot=0.25470(Cavuoti et al. 2014) Real time updated cover map and OT position are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3062088 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/43006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41083] GRB 251205A: Swift detection of a burst with an optical afterglow
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43005 SUBJECT: GRB 251205A: Swift detection of a burst with an optical afterglow DATE: 25/12/06 00:02:39 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> S. Lanava (PSU), S. Dichiara (PSU), C. Gronwall (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 23:39:47 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251205A (trigger=1420873). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 200.243, +29.962 which is RA(J2000) = 13h 20m 58s Dec(J2000) = +29d 57' 45" 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 30 sec. The peak count rate was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 23:42:07.0 UT, 139.8 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 200.2707, 29.9296 which is equivalent to: RA(J2000) = 13h 21m 4.97s Dec(J2000) = +29d 55' 46.6" with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 145 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 2.5 s image was 1.44e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 148 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 13:21:05.34 = 200.27223 DEC(J2000) = +29:55:44.0 = 29.92888 with a 90%-confidence error radius of about 0.75 arc sec. This position is 5.4 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.54 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.014. Burst Advocate for this burst is S. Lanava (sml7284 AT psu.edu). 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/43005. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41082] Swift GRB251205.99: Global MASTER-Net observations report
by GCN Circulars 05 Dec '25

05 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43004 SUBJECT: Swift GRB251205.99: Global MASTER-Net observations report DATE: 25/12/05 23:48:53 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 Swift GRB251205.99 (trigger No 1420873,13h 20m 58.42s , +29d 57m 45.0s, R=0.05) errorbox 19 sec after notice time and 92 sec after trigger time at 2025-12-05 23:41:19 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 68 deg. The sun altitude is -51.1 deg. The galactic latitude b = 83 deg., longitude l = 55 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3062088 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 103 | MASTER-Kislovodsk | P- | 20 | 16.6 | 103 | MASTER-Kislovodsk | P| | 20 | 16.5 | 131 | MASTER-Kislovodsk | P- | 20 | 16.3 | 131 | MASTER-Kislovodsk | P| | 20 | 16.5 | 164 | MASTER-Kislovodsk | P- | 30 | 16.8 | 164 | MASTER-Kislovodsk | P| | 30 | 16.8 | 208 | MASTER-Kislovodsk | P- | 40 | 16.8 | 208 | MASTER-Kislovodsk | P| | 40 | 16.8 | 261 | MASTER-Kislovodsk | P- | 50 | 17.0 | 261 | MASTER-Kislovodsk | P| | 50 | 17.0 | 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/43004. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41081] GRB 251126B: Fermi GBM Final Localization
by GCN Circulars 05 Dec '25

05 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43003 SUBJECT: GRB 251126B: Fermi GBM Final Localization DATE: 25/12/05 17:22:08 GMT FROM: Boyan A. Hristov at UAH <bah0046(a)uah.edu> The Fermi GBM team reports the detection of a likely LONG GRB "At 15:57:02.80 UT on 26 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251126B (trigger 785865427/251126665). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 321.15, Dec = -28.24 (J2000 degrees, equivalent to J2000 21h 24m, -28d 14'), with a statistical uncertainty of 14.32 degrees. The angle from the Fermi LAT boresight is 73 degrees. The skymap can be found here: sftp://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251126665/q… The HEALPix FITS file, including the estimated localization systematic, can be found here: sftp://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251126665/q… The GBM light curve can be found here: sftp://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251126665/q…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43003. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41080] GRB 251203A: Insight-HXMT/HE detection
by GCN Circulars 05 Dec '25

05 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43002 SUBJECT: GRB 251203A: Insight-HXMT/HE detection DATE: 25/12/05 15:48:13 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-03T08:18:50.250 (T0), Insight-HXMT/HE detected a long burst, GRB 251203A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42968), SVOM/GRM (Ren et al., GCN#42995), and GECAM-B (Ren et al., GCN#42996). The Insight-HXMT/HE light curve mainly consists of multiple pulses with T90 of 11 +5/-5 s. The 1s peak rate, measured from T0-0.5 s, is 351 cnts/sec. Insight-HXMT/HE detected a total of 1399 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251203A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Low-Gain mode with the energy range of about 300-3000 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/43002. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41079] GRB 251203C: SVOM/ECLAIRs refined analysis
by GCN Circulars 05 Dec '25

05 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43001 SUBJECT: GRB 251203C: SVOM/ECLAIRs refined analysis DATE: 25/12/05 14:17:52 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> N. Dagoneau (CEA), M. Brunet, N. A. Webb (IRAP) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251203C (SVOM burst-id sb25120305). The burst that triggered ECLAIRs onboard (GCN 42976) consists of a multiple peaks lightcurve with a duration of T90 = 13.0 -4.7/+1.6 s in the 4-120 keV energy band. The time-averaged spectrum (from T0-3.59s to T0+9.49s) in the energy range 5-120 keV is best fit by a simple power-law model with a photon index -1.98 -0.17/+0.18. The total fluence in the 4-120 keV band is (3.63 -0.59/+0.27)e-7 erg/cm^2. All the quoted errors are at the 68% confidence level. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43001. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41078] SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
by GCN Circulars 05 Dec '25

05 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43000 SUBJECT: SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate DATE: 25/12/05 13:40:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> W. J. Xie, D. H. Zhao (NAOC), S. Schanne (CEA/Irfu), Marius Brunet, J.-L. Atteia (IRAP) report on behalf of the SVOM mission team: At 2025-12-05T02:57:15 UTC (T0), SVOM/ECLAIRs triggered and located a possible X-ray transient (SVOM burst-id sb25120502). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The transient was only detected by the Image Trigger (IMT), which produced a sequence of 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 6.58 in the [8-50] keV energy band over a time window of 20.48 seconds starting at 2025-12-05T02:56:55. After the reception over X-band of the photon by photon data, those have been replayed on ground in the Offline trigger as well as a ground copy of the On-board trigger, by varying the trigger timescales. The event is still detected as a point-like source at the same position in the same energy band as given by the on-board trigger, over the same 20.48 s time-window. The sky images obtained are clean and show no sign of the source before and after that time period. The localization of the best alert is R.A., Dec. 80.9924, -18.2171 degrees: R.A. (J2000) = 5h23m58.16s Dec. (J2000) = -18d13m01.48s with a 90% confidence level (C.L.) radius of 11.88 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this burst. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being. We notice the presence of the High Proper Motion star LP 777-23, located at 9.3 arcmin from the trigger position. 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 contact point for this alert is Wenjin XIE: xiewj(a)bao.ac.cn Please contact by the email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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