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

[vsnet-grb-info 43203] EP260618a: COLIBRÍ optical counterpart candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44988 SUBJECT: EP260618a: COLIBRÍ optical counterpart candidate DATE: 26/06/19 05:09:23 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP260618a (Yang et al., GCN Circ. 44978), possibly associated with GRB 260618A (Fermi GBM team GCN Circ. 44973), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-19 03:44 to 04:55 UTC (from 19.15 to 20.34 hours after the trigger) and obtained 55 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the ASU COLIBRÍ pipeline The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction, which is particularly significant in this direction (A_r = 1.1 mag; Schlafly & Finkbeiner 2011) due to the proximity of the field to the Galactic plane. We detect an uncatalogued source, absent in Pan-STARRS template images and and located within the WXT error region (Yang et al., GCN Circ. 44978) at: RA(J2000) = 18:26:43.13 = 276.6797 degrees, Dec(J2000) = +23:50:37.8 = 23.8438 degrees, with an uncertainty of 0.5 arcsec. The preliminary magnitudes derived for this source are: r = 21.90 +/- 0.04, z = 21.49 +/- 0.08. We therefore suggest that this source is the optical counterpart of EP260618a. Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/44988. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43202] GRB 260616A: NuSTAR detection of prompt emission
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44987 SUBJECT: GRB 260616A: NuSTAR detection of prompt emission DATE: 26/06/19 03:34:34 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260616A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-06-16T03:21:25.62 UTC, shows a detection of GRB 260616A, also detected by Fermi-GBM (Fermi GBM Team, GCN 44948), GECAM-B (Guo et al., GCN 44964), Konus-Wind (Ridnaia et al., GCN 44967), and Insight-HXMT (Wang et al., GCN 44980). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a burst lasting for about 100-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors. The Fermi-LAT localization (Lopez et al., GCN 44960) at RA = 93.53, Dec = -32.07 implies an offset from the NuSTAR boresight of 133-deg (i.e. from the backside) and an offset from the geocenter of 86-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260616A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44987. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43201] GRB 260614B: NuSTAR detection of prompt emission
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44986 SUBJECT: GRB 260614B: NuSTAR detection of prompt emission DATE: 26/06/19 03:32:52 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260614B in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-06-14T13:49:47.0 UTC, shows a detection of GRB 260614B, also detected by Fermi-GBM (Fermi GBM Team, GCN 44937), SVOM (Godet et al., GCN 44938), and GECAM-B (Luo et al., GCN 44945). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a burst lasting for about 20-s, consistent with the Fermi and GECAM-B lightcurve. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors. The SVOM/VT counterpart (Palmerio et al., GCN 44939) at RA = 353.90883, Dec = -54.11628 implies an offset from the NuSTAR boresight of 99-deg (i.e. from the side) and an offset from the geocenter of 125-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260614B Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44986. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43200] GRB 260619A: SVOM possible detection of a faint burst
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44985 SUBJECT: GRB 260619A: SVOM possible detection of a faint burst DATE: 26/06/19 03:10:53 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Hatsune Goto (RIKEN), Jun Yang (ZZU), Kuan Liu (GXU), Zhiyong Liu (GZNU) report on behalf of the SVOM mission team: At 2026-06-19T02:12:40 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260619A (SVOM burst-id sb26061901). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst 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 6.90 in the [8-50] keV energy band over a time window of 40.96 seconds starting at 2026-06-19T02:11:59. The localization of the best alert is R.A., Dec. 359.0538, -15.3917 degrees: R.A. (J2000) = 23h56m12.91s Dec. (J2000) = -15d23m30.15s with a 90% confidence level (C.L.) radius of 11.33 arcmin (including systematic error of 2 arcmin added in quadrature). There’re 3 High Proper Motion Stars in the ECLAIRs error box: LP 764-29 GR* 276 BD-16 6388 These sources may cause this trigger. Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. 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 Burst Advocate (BA) on shift for this alert is Kuan Liu: liuk(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44985. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43199] IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44984 SUBJECT: IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/06/19 01:32:40 GMT FROM: syan079(a)icecube.wisc.edu The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-260610A (https://gcn.nasa.gov/circulars/44899) in a time range of 1000 seconds centered on the alert event time (2026-06-10 19:54:21.035 UTC to 2026-06-10 20:11:01.035 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-260610A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260610A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 6e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-06-09 20:02:41.035 UTC to 2026-06-11 20:02:41.035 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.7e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260610A in a 2 day time window. 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. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/44984. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43198] GRB 260618B: Fermi-LAT detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44983 SUBJECT: GRB 260618B: Fermi-LAT detection DATE: 26/06/18 22:53:02 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> R. Gupta (NASA/GSFC), A. Holzmann Airasca (UniTrento and INFN Bari), and N. Di Lalla (Stanford University) report on behalf of the Fermi-LAT collaboration: At 16:55:04.71 UT on June 18th, 2026, Fermi-LAT detected high-energy emission from GRB 260618B, which was also detected by Fermi-GBM (trigger 803494509/260618705, GCN #44979). The best LAT on-ground location is found to be RA, Dec = 354.35, -44.88 (J2000) with an error radius of 0.10 deg (90 % containment, statistical error only). This was 16 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 0 - 100 s after the GBM trigger is (1.99 ± 0.56)E-5 ph/cm2/s. The estimated photon index above 100 MeV is -1.82 ± 0.21. The highest energy photon has an energy of 6.7 GeV and occurs at 1.8 s after trigger time. The Fermi-LAT point of contact for this burst is Samantha López (lopez(a)llr.in2p3.fr) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/44983. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43197] IPN triangulation of GRB 260617A (short)
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44982 SUBJECT: IPN triangulation of GRB 260617A (short) DATE: 26/06/18 21:50:23 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, 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 260617A (Fermi-GBM detection: Fermi GBM team, GCN 44969; Godwin & Meegan, GCN 44972) was detected by Fermi (GBM trigger 803425008), Konus-Wind, and Mars-Odyssey (HEND) at about 77803 s UT (21:36:43). We have triangulated it to the 3 sigma localization region whose area is 3360 sq. arcmin, and its maximum dimension is 4.4 deg (the minimum one is 12.9 arcmin). A triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB260617_T77808/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/44982. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43196] GRB 260610B/AT 2026owq: FTW optical and NIR observations
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44981 SUBJECT: GRB 260610B/AT 2026owq: FTW optical and NIR observations DATE: 26/06/18 19:32:02 GMT FROM: Julius Gassert at Ludwig-Maximilians-Universität München <julius.gassert(a)campus.lmu.de> Julius Gassert (LMU/CMU), Malte Busmann (LMU), Brendan O'Connor (CMU), Daniel Gruen (LMU), Xander Hall (CMU), and Antonella Palmese (CMU) report: We observed the afterglow of GRB260610B (AT 2026owq) (Fermi/GBM; GCN 44901; O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946), with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the g, r, i, z, and J bands for 8x 180s starting at 2026-06-17 22:48 UT. As previously reported (Gillanders et al., GCN 44955; Angulo et al., GCN44958; Dimple et al., GCN44959; Moksvitin et al. GCN44963; Pankov et al., GCN44977), we also detect the rebrightening/flattening in all bands, althought the i-band detection is marginal. In the r band, we detect the counterpart at: r = 21.31 +/- 0.10 AB mag The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Silona Wilke from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44981. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43195] GRB 260616A: Insight-HXMT detection
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44980 SUBJECT: GRB 260616A: Insight-HXMT detection DATE: 26/06/18 18:19:26 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Hao-Xuan Guo, Zheng-Hang Yu, Shao-Lin Xiong, Cheng-Kui Li, and Chao Zheng report on behalf of the Insight-HXMT team: At 2026-06-16T03:22:29.650 (T0), Insight-HXMT/HE detected GRB 260616A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#44948), Fermi/LAT (S. Lopez et al., GCN #44960), GECAM-B (Hao-Xuan Guo et al., GCN #44964), Konus-Wind (A. Ridnaia et al., GCN#44976) and SVOM/GRM. The Insight-HXMT/HE light curve mainly consists of a set of dense spikes with a T90 of 76.0 +4.5/-4.0 s. The 1s peak rate, measured from T0+14.8 s, is 5435 cnts/sec. The total counts from this burst is 178317 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260616A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 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/44980. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43194] GRB 260618B: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44979 SUBJECT: GRB 260618B: Fermi GBM Final Real-time Localization DATE: 26/06/18 17:07:30 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 16:55:04 UT on 18 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618B (trigger 803494509.712104 / 260618705). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 351.1, Dec = -44.1 (J2000 degrees, equivalent to J2000 23h 24m, -44d 06'), with a statistical uncertainty of 1.8 degrees. The angle from the Fermi LAT boresight is 18.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618705/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618705/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618705/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44979. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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