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

[vsnet-grb-info 41284] EP251221a: Global MASTER-Net observations report
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43198 SUBJECT: EP251221a: Global MASTER-Net observations report DATE: 25/12/23 02:27:30 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP251221a ( EP Team et al., GCN 43178) errorbox 25137 sec after notice time and 48513 sec after trigger time at 2025-12-22 11:07:39 UT, with upper limit up to 14.1 mag. The observations began at zenith distance = 80 deg. The sun altitude is -18.4 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251221a errorbox 77221 sec after notice time and 1 days 14196 sec after trigger time at 2025-12-23 01:35:42 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 48 deg. The sun altitude is -32.6 deg. The galactic latitude b = 12 deg., longitude l = 193 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3080482 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 48543 | 2025-12-22 11:07:39 | MASTER-Tunka | (06h 57m 20.46s , +23d 03m 38.7s) | C | 60 | 14.1 | 48543 | 2025-12-22 11:07:39 | MASTER-Tunka | (06h 57m 34.89s , +22d 56m 36.5s) | C | 60 | 13.3 | 52254 | 2025-12-22 12:08:30 | MASTER- | (07h 00m 06.39s , +23d 40m 37.8s) | C | 180 | 18.9 | 52254 | 2025-12-22 12:08:30 | MASTER- | (07h 00m 04.96s , +24d 36m 38.8s) | C | 180 | 18.4 | 100687 | 2025-12-23 01:35:42 | MASTER-Kislovodsk | (06h 57m 08.12s , +23d 26m 58.0s) | C | 180 | 18.2 | 100687 | 2025-12-23 01:35:42 | MASTER-Kislovodsk | (06h 56m 59.41s , +23d 49m 39.5s) | C | 180 | 18.3 | 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/43198. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41283] GRB 251222A: PRIME near-infrared detection
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43197 SUBJECT: GRB 251222A: PRIME near-infrared detection DATE: 25/12/23 01:48:17 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> J. Durbak (UMD), N. Passaleva (U Rome), O. Guiffreda (UMD), M. El Kabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Fermi GBM detection (GCN 43186) and SVOM (Yang et al., GCN 43188), we observed the transient field in Y, J and H filters with PRIME ~2 hours after Fermi and SVOM detections. At the position of the optical counterpart reported by SVOM/VT (Palmerio et al., GCN 43189), we detect an uncatalogued source in J band. Using nearby VISTA Hemispherical Survey (VHS) stars for preliminary calibration we derive the following magnitudes, not corrected for Galactic extinction: Filter | Mag(AB) | -------|----------------| J | 18.04 +/- 0.02 | Further observations are planned. PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024, Sumi et al. 2025). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41282] GRB 251222A: PRIME near-infrared detection
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43197 SUBJECT: GRB 251222A: PRIME near-infrared detection DATE: 25/12/23 01:48:17 GMT FROM: Joe Durbak at UMD <gcn.joedurbak(a)gmail.com> J. Durbak (UMD), N. Passaleva (U Rome), O. Guiffreda (UMD), M. El Kabir (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Fermi GBM detection (GCN 43186) and SVOM (Yang et al., GCN 43188), we observed the transient field in Y, J and H filters with PRIME ~2 hours after Fermi and SVOM detections. At the position of the optical counterpart reported by SVOM/VT (Palmerio et al., GCN 43189), we detect an uncatalogued source in J band. Using nearby VISTA Hemispherical Survey (VHS) stars for preliminary calibration we derive the following magnitudes, not corrected for Galactic extinction: Filter | Mag(AB) | -------|----------------| J | 18.04 +/- 0.02 | Further observations are planned. PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024, Sumi et al. 2025). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41281] EP251221a: NOT optical upper limit
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43196 SUBJECT: EP251221a: NOT optical upper limit DATE: 25/12/23 01:19:56 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L. B. He, J. An, X. Liu, D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), J. A. Chacon (PUC), F. E. Bauer (SSI and UTA), P. G. Jonker (Radboud), A. Kadela (NOT and NBI), report on behalf of a larger collaboration: We observed the field of EP251221a (Dai et al., GCN 43178) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r and z band, starting on 2025-12-22 at 03:00:12 UTC (5.35 hr after the WXT trigger). No new optical source is detected within the EP/WXT error circle. And we obtained the following upper limits: | Band | t_mid - T0 (hr) | Exposure time | 5-sigma upper limit | |--|--|--|--| | r | 5.47 | 1x300s+1x180s | 23.5 | | r | 6.25 | 3x300s | 23.8 | | z | 7.21 | 5x200s | 22.3 | calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41280] GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43195 SUBJECT: GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation. DATE: 25/12/23 01:14:18 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 251222A detected by SVOM/ECLAIRs (Yang et al., GCN 43188) and Fermi Gamma-ray Burst Monitor (GCN 43186) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-12-22 18:27:54 UT (approximately 1.37 hours after burst) stacking a sets of unfiltered CCD image. The observations were carried out with clear skies, good visibility conditions and light gusts of wind. The OT was detected at the following position: RA (J2000.0) 05h 08m 46.7s Decl. (J2000.0) -07° 12' 48.4" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Mag. err. 2025-12-22 18:56:55 UT 1.85 30x60s CR 18.70 +/- 0.09 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Palmerio et al. (GCN 43189); An et al. (GCN 43194). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43195. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41279] GRB 251222A: NOT optical observations
by GCN Circulars 22 Dec '25

22 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43194 SUBJECT: GRB 251222A: NOT optical observations DATE: 25/12/22 23:07:49 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), B. Schneider (LAM), A. Saccardi (CEA/Irfu), L. Cotter (UCD), M. A. Diaz Teodori, A. Nitindala (University of Turku), report on behalf of a larger collaboration: We observed the optical counterpart (Palmerio et al., GCN 43189) of GRB 251222A (Yang et al., GCN 43188; Fermi GBM team, GCN 43186) using the Nordic Optical Telescope equipped with the Standby Camera (StanCam). A series of 3 x 300s exposures were taken in the R band starting at 2025-12-22T21:34:54. The afterglow is well detected in the individual images with an AB magnitude of R = 18.96 +/- 0.02 at a mid-time of 4.53 hr after the trigger. Our photometry was calibrated using nearby stars from the Pan-STARRS catalog and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43194. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41278] IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 22 Dec '25

22 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43193 SUBJECT: IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility DATE: 25/12/22 21:43:04 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-251218A (Zegarelli et. al, GCN 43151) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the r-band beginning at 2025-12-19 04:45 UTC, approximately 8.4 hours after event time. We covered 100.0% (1.1 sq deg) of the reported localization region. This estimate accounts for chip gaps. The exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. This is consistent with previously reported upper limits (Antier et al. 2025, GCN 43153). Observations of this field will continue as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/43193. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41277] IPN triangulation of GRB 251220B (short)
by GCN Circulars 22 Dec '25

22 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43192 SUBJECT: IPN triangulation of GRB 251220B (short) DATE: 25/12/22 21:25:26 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 251220B (Fermi/GBM detection: The Fermi GBM team, GCN 43160; SVOM/GRM observation: Wang et al., GCN 43171) was detected by Fermi(GBM trigger 787966689), Konus-Wind, Swift(BAT), SVOM (GRM), and Mars-Odyssey (HEND), at about 85085 s UT (23:38:05). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 246.020 (16h 24m 05s) +44.550 (+44d 33' 00") Corners: 242.980 (16h 11m 55s) +43.398 (+43d 23' 51") 248.478 (16h 33m 55s) +45.405 (+45d 24' 19") 249.037 (16h 36m 09s) +45.540 (+45d 32' 24") 243.550 (16h 14m 12s) +43.587 (+43d 35' 13") --------------------------------------------- The error box area is 597 sq. arcmin, and its maximum dimension is 4.82 deg (the minimum one is 2.3 arcmin). The Sun distance was 71 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB251220_T85082/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/43192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41276] GRB 251222A: Swift ToO observations
by GCN Circulars 22 Dec '25

22 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43191 SUBJECT: GRB 251222A: Swift ToO observations DATE: 25/12/22 20:09:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event GRB 251222A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021895 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41275] GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
by GCN Circulars 22 Dec '25

22 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43190 SUBJECT: GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712) DATE: 25/12/22 18:24:42 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger at 17:05:51 on 22 Dec. 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 76.6 deg Decl.(2000.0) = -7.7 deg The 1 sigma statistical error radius is 2.5 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB251222712/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB251222712/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB251222712/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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