May 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 42590] IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 05 May '26

05 May '26

TITLE: GCN CIRCULAR NUMBER: 44464 SUBJECT: IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 26/05/05 01:46:29 GMT FROM: jliao(a)icecube.wisc.edu The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 26-05-04 at 21:11:20.90 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of None events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/142545_58544625.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 26-05-04 Time: 21:11:20.90 UT RA: 246.99 (+0.86/-0.80 deg 90% PSF containment) J2000 Dec: 54.87 (+0.46/-0.47 deg 90% PSF containment) J2000 One gamma-ray source from the Fermi 4FGL-DR4 catalog is located within the 90% uncertainty region of this event: 4FGL J1626.0+5436 , at RA = 246.51° and Dec = 54.61° (J2000), with an angular separation of 0.38° from the best-fit event position. As announced in GCN Circular 43419 (https://gcn.nasa.gov/circulars/43419) IceCube alert notices for high-energy track alerts are now also streamed via Kafka. IceCube Gold/Bronze track alerts are available on the Kafka topic 'gcn.notices.icecube.gold_bronze_track_alerts'. The probability distribution of the true neutrino direction, allowing the extraction of precise 90% containment regions around the best-fit direction, is now available for revised reconstruction of high-energy track alerts. The corresponding sky map is distributed as a FITS file and follows the explicit naming convention IceCube-YYMMDDX, where YYMMDD indicates the date of the event and X is a letter distinguishing multiple alerts on the same day. The download link is provided through the GCN schema distributed via Kafka. Detailed documentation describing the alert distribution, schemas, and probability maps is available at: https://gcn.nasa.gov/missions/icecube. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/44464. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42589] Konus-Wind detection of GRB 260415C
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44463 SUBJECT: Konus-Wind detection of GRB 260415C DATE: 26/05/04 20:18:18 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> 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 260415C triggered Konus-Wind at T0=27659.163 s UT (07:40:59.163). The burst light curve shows a single pulse which starts at ~T0-2.5 s and has a total duration of ~11.3 s. The emission is seen up to 2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260415_T27659/ As observed by Konus-Wind, the burst had the total fluence of 3.64(-0.42,+0.54)x10^-6 erg/cm2, and the 64-ms peak flux, measured from T0-0.446 s, of 1.56(-0.41,+0.45)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 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 = -0.06(-0.45,+0.60), the high energy photon index beta = -2.91(-0.94,+0.36), the peak energy Ep = 105(-11,+12) keV (chi2 = 92/77 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/44463. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42588] GCN Announcement: New BOOM Notices and Schema v7.0.0
by GCN Announcements 04 May '26

04 May '26

The GCN Team is pleased to announce a new Notice Type and a schema release. BOOM Cross-Correlated Optical Transient Notices The Burst & Outburst Observations Monitor (BOOM)/Babamul Team (https://www.ztf.caltech.edu/ztf-boom-babamul.html) and the GCN Team are pleased to announce the availability of a new notice type via the new GCN in JSON format. BOOM provides real-time brokering, archival context, and coordination tools that enable rapid identification, vetting, and follow-up of astrophysical transients. BOOM is the software stack operating to enable a multi-survey alert broker and data archive (Babamul) that ingests and combines alerts from the Zwicky Transient Facility (ZTF) and the Vera C. Rubin Observatory alert stream. BOOM is contributing a GCN Notices stream, where cross-matches from the BOOM fast transient stream (which analyzes ZTF and LSST alert streams) are checked for (i) gravitational-wave alert candidates consistent with a binary neutron star merger or neutron star-black hole merger and (ii) gamma-ray bursts detected by Fermi, SVOM, and Swift. This enables rapid cross-identification of events across experiments and observatories, enhancing situational awareness and time-critical response for the broader transient astronomy community. Alert includes localization, photometry, cross-matches with other GCN Notices, and classification scores from machine-learning models. BOOM notices are published on the GCN Kafka topic gcn.notices.boom.alert. See the BOOM mission page (https://gcn.nasa.gov/missions/boom) for a more extensive description of the information provided in these new notices. Schema v7.0.0 GCN Schema v7.0.0 is available with recent changes including new Notice types and a modified and generalized Spectral core schema (Release Notes; https://github.com/nasa-gcn/gcn-schema/releases/tag/v7.0.0) For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42587] GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44462 SUBJECT: GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN DATE: 26/05/04 19:46:05 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> N. Pankov (IKI), A. Pozanenko (IKI), A. Volnova (IKI), E. Schekotikhin (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), V. Rumyantsev (CrAO), A. Novichonok (KIAM), A. Kochergin (UAFO IAA), I. Sokolov (INASAN), M. Krugov (FAI), R. Inasaridze (AbAO), A. Tarasenkov (INASAN) report on behalf of IKI GRB-FuN: We observed the optical counterpart AT2026fgk (a.k.a. GOTO26buh, O'Neill et al. 2026, TNS Discovery Report 294132; Hinds et al., AstroNote 2026-65; Konno et al., GCN 43974) associated with GRB 260310A (The Fermi GBM team, GCN 43951; Salunke et la., GCN 43958; Hamburg & Meegan, GCN 43975; Jayaraman et al., GCN 43994). Observations began on March 13, 2026, and continue to this day. Observations were performed with the following telescopes: AZT-33IK (Mondy), Zeiss-1000 (SAO RAS), Zeiss-1000 (Koshka), ZTSh (CrAO), ORI-50 (UAFO), Zeiss-2000 (Terskol), AZT-20 (Assy), AS-32 (AbAO) with BR-filters, and BVRI-filters on a few epochs. We clearly detect the counterpart (Lipunov et al., GCN 43954, 43978; Martin-Carrillo et al., GCN 43979, 44000; Moreno Méndez et al., GCN 43979; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991, 44059; Jin-Ji Li et al., GCN 43993; Stein et al., GCN 43996; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo, GCN 44003; Brivio et al., GCN 44004; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021, 44067; Pawar et al., GCN 44022; Belkin & Shrestha, GCN 44043; H. L. Li et al., GCN 44044; Gupta et al., GCN 44051; Passaleva et al., GCN 44058, 44104; Volnova et al., GCN 44060; Busmann et al., GCN 44061; Zheng & Filippenko, GCN 44065; Pankov et al., GCN 44073; Serrau et al., GCN 44112; Kang et al., GCN 44119; Effress et al., GCN 44122; Guelfand et al., GCN 44125; O'Connor et al., GCN 44137; Liu et al., GCN 44172; Freeberg et al., GCN 44208). We confirm the break reported by Perly at al. (GCN 44096) on the 8th day after the trigger. After subtracting the image using the template obtained on April, 21 in the R filter with AZT-33IK, we constructed the afterglow + supernova light curve (LC). We note, that the point source is still clearly detected on the image on May, 02. We note that the afterglow power law decay index of -2.1 is steeper than reported by Perly at al. (GCN 44096) and may be affected by the still glowing optical counterpart. Subtracting the power-law afterglow with the power law decay index of -2.1 from the light curve gives us a possible supernova light curve, shown in https://heaiki.ru/lvc/GRB260310A/GRB260310A_subtracred_host_and_PL__aftergl… (for the LC construction we use only observations obtained with AZT-033IK, Mondy.) Thus we can tentatively confirm the maximum of bump which was suggested as possible SN associated with GRB 260310A in R-filter of about 21 days after the GRB trigger reported earlier (Freeberg et al., GCN 44248), however more faint and with apparent magnitude of about R ~ 21.8. Thus absolute magnitude at the redshift of z=0.153 (Hinds et al., GCN 43977; de Ugarte Postigo et al., GCN 43984) would be not fainter than M_R = -17.5. Initially SN rising was suggested by SED evolution (de Ugarte Postigo et al., GCN 44124). We continue to monitor the optical counterpart of the GRB 260310A. View this GCN Circular online at https://gcn.nasa.gov/circulars/44462. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42586] Konus-Wind detection of GRB 260411C
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44461 SUBJECT: Konus-Wind detection of GRB 260411C DATE: 26/05/04 19:38:56 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 260411C triggered Konus-Wind at T0=21236.871 s UT (05:53:56.871). The burst light curve shows a single pulse which starts at ~T0-14.9 s and has a total duration of ~24.3 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260411_T21236/ As observed by Konus-Wind, the burst had the total fluence of 1.31(-0.08,+0.08)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+1.584 s, of 7.72(-0.94,+0.93)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 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 = -1.54(-0.09,+0.08), the high energy photon index beta = -3.23(-6.77,+0.37), the peak energy Ep = 105(-6,+8) keV (chi2 = 85/81 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/44461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42585] GRB 260502A: Fermi GBM Final Localization
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44447 SUBJECT: GRB 260502A: Fermi GBM Final Localization DATE: 26/05/03 05:20:13 GMT FROM: Rushikesh Sonawane at IISER TVM <rushikesh23(a)iisertvm.ac.in> The Fermi GBM team reports the detection of a likely SHORT GRB "At 05:01:00.25 UT on 02 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260502A (trigger 799390865/260502209). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 283.76, Dec = 57.62 (J2000 degrees, equivalent to J2000 18h 55m, +57d 37′), with a statistical uncertainty of 13.77 degrees. The angle from the Fermi LAT boresight is 23 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260502209/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260502209/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260502209/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44447. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42584] GRB 260504B: REM optical/NIR observations
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44460 SUBJECT: GRB 260504B: REM optical/NIR observations DATE: 26/05/04 15:24:20 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 260504B detected by SVOM/ECLAIRs (Saccardi et al., GCN 44454) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried out in the g, r, i, z, and H bands, started on 2026 May 04 at 09:41:12 UT (i.e. 9.9 min after the burst), and lasted for about 1.5 hours. From preliminary inspection, we do not detect any counterpart within the SVOM/ECLAIRs and SVOM/MXT error circles down to the following 3sigma limits: r > 19.5 (AB; calibrated against the SkyMapper catalogue), at a mid-time of 33.8 min after the trigger; H > 15.3 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 13.3 min after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/44460. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42583] IPN triangulation of GRB 260429A
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44459 SUBJECT: IPN triangulation of GRB 260429A DATE: 26/05/04 15:06:16 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(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, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, 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, 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 bright, short-duration GRB 260429A (Ferm-GBM detection: The Fermi GBM team, GCN 44425; Scotton, GCN 44430; SVOM-GRM detection: Yu et al., GCN 44439) was detected by Fermi (GBM trigger 799197847), Konus-Wind, SVOM (GRM), and Mars-Odyssey (HEND) at about 84242 s UT (23:24:02). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 281.153 (18h 44m 37s) +17.279 (+17d 16' 44") Corners: 281.115 (18h 44m 28s) +17.444 (+17d 26' 37") 281.161 (18h 44m 39s) +17.398 (+17d 23' 52") 281.192 (18h 44m 46s) +17.114 (+17d 06' 50") 281.146 (18h 44m 35s) +17.160 (+17d 09' 36") --------------------------------------------- The error box area is 40 sq. arcmin, and its maximum dimension is 20 arcmin (the minimum one is 2.3 arcmin). The Sun distance was 109 deg. This localization may be improved. A triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB260429_T84245/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/44459. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42582] IPN triangulation of GRB 260428A
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44458 SUBJECT: IPN triangulation of GRB 260428A DATE: 26/05/04 15:04:29 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, C. Wang (IHEP), S. Xiong (IHEP), S. Zhang (IHEP), J. Wei (NAOC), B. Cordier (CEA) on behalf of the SVOM-GRM 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 260428A (Fermi-GBM detection: Fermi GBM team, GCN Circ. 44415; AstroSat-CZTI detection: Goyal et al., GCN Circ. 44421; GECAM-B detection: Wang et al., GCN Circ. 44423; SVOM/GRM observation: Wang et al., GCN Circ. 44424) was detected by Fermi (GBM), Konus-Wind, AstroSat (CZTI), GECAM-B, SVOM (GRM), and Mars-Odyssey (HEND) at about 51636 s UT (14:20:36). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 283.386 (18h 53m 33s) +0.365 ( +0d 21' 53") Corners: 283.274 (18h 53m 06s) +1.978 ( +1d 58' 41") 283.221 (18h 52m 53s) +2.065 ( +2d 03' 56") 283.504 (18h 54m 01s) -1.335 ( -1d 20' 06") 283.558 (18h 54m 14s) -1.435 ( -1d 26' 07") --------------------------------------------- The error box area is 561 sq. arcmin, and its maximum dimension is 3.5 deg (the minimum one is 3 arcmin). The Sun distance was 111 deg. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260428_T51639/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/44458. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42581] GRB 260504B: AST3-2 i-band upper limit
by GCN Circulars 04 May '26

04 May '26

TITLE: GCN CIRCULAR NUMBER: 44457 SUBJECT: GRB 260504B: AST3-2 i-band upper limit DATE: 26/05/04 15:02:23 GMT FROM: Tianrui Sun at Purple Mountain Obs,CAS <trsun(a)pmo.ac.cn> Tian-Rui Sun, Yan-Long Hua (Purple Mountain Observatory, CAS), Kun Ma, Jiali Chen, Kai-wen Zheng, Hongjian Guo, Ben Liu, Shuping Wang, Huiping Jin, Jiaheng Liu, Haoyu Yan, Jiajie Yang, Xiao-Yan Li (Nanjing Institute of Astronomical Optics & Technology, CAS), Jin-Jun Geng, Wenlong Zhang, Xue-Feng Wu (Purple Mountain Observatory, CAS), report on behalf of the AST3 Team: Following the detection of GRB 260504B by ECLAIRs aboard SVOM (A. Saccardi et al., GCN 44454), we carried out follow-up observations using the Antarctic Survey Telescope AST3-2 located at Dome A, Antarctica (Lat. −80.4173 deg, Long. 77.0950 deg). Observations began at 2026-05-04 09:48:50 UT. No significant optical counterpart was detected within the ECLAIRs error circle (~4.91 arcmin radius) and the MXT error circle (~167 arcsec), based on comparisons with Gaia DR3 and archival SkyMapper cutout images. The stacked image with a total exposure time of 7170 s in the i-band reached a 5σ limiting magnitude of ~19.7.This result is consistent with the non-detections reported by MASTA-OAFA (F. Podesta et al., GCN 44455) and by LCO (D. Turpin et al., GCN 44456). Photometric calibration was performed using the ATLAS Reference Catalog (Tonry et al. 2018). We thank Prof. Michael Ashley (UNSW) for his continuous support in the operation of AST3-2. View this GCN Circular online at https://gcn.nasa.gov/circulars/44457. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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