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

[vsnet-grb-info 43003] GRB 260608A: SVOM detection of a burst
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44870 SUBJECT: GRB 260608A: SVOM detection of a burst DATE: 26/06/08 12:08:17 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, L. Bouchet (IRAP), C.-W. Wang (IHEP) D.-F. Kong (GXU) report on behalf of the SVOM mission team: At 2026-06-08T11:35:32 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260608A (SVOM burst-id sb26060803), which is also detected by Fermi/GBM (GCN 44868). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 34 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 24.71 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2026-06-08T11:35:14. The localization of the best alert is R.A., Dec. 81.3711, -48.3879 degrees: R.A. (J2000) = 5h25m29.07s Dec. (J2000) = -48d23m16.62s with a 90% confidence level (C.L.) radius of 3.70 arcmin (including systematic error of 2 arcmin added in quadrature). TThe SVOM/ECLAIRs light curve showed a multiple peak structure with a T90 duration of about 46.839 (-2.959 +3.411) s. This burst was also detected by SVOM/GRM with a significance of 18.20. The SVOM/GRM light curve showed a multiple peak structure with a T90 duration of about 53.73 (-2.457 +2.459) s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260608A.png Due to Sun constraint, no X-ray observation could be performed by SVOM/MXT and no optical observation could be performed by SVOM/VT for the time being. 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 Chenwei Wang: cwwang(a)ihep.ac.cn Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43002] GRB 260608A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44869 SUBJECT: GRB 260608A: Fermi GBM Final Real-time Localization DATE: 26/06/08 11:47:57 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 11:35:31 UT on 8 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260608A (trigger 802611336.05914 / 260608483). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.4, Dec = -45.2 (J2000 degrees, equivalent to J2000 05h 13m, -45d 12'), with a statistical uncertainty of 3.2 degrees. The angle from the Fermi LAT boresight is 29.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43001] GRB 260608A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44868 SUBJECT: GRB 260608A: Fermi GBM Final Real-time Localization DATE: 26/06/08 11:46:30 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 11:35:31 UT on 8 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260608A (trigger 802611336.05914 / 260608483). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 78.4, Dec = -45.2 (J2000 degrees, equivalent to J2000 05h 13m, -45d 12'), with a statistical uncertainty of 3.2 degrees. The angle from the Fermi LAT boresight is 29.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260608483/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43000] EP260605a: EP-FXT follow-up observation
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44867 SUBJECT: EP260605a: EP-FXT follow-up observation DATE: 26/06/08 10:47:23 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> A.Li (BNU), C. Y. Wang (THU), Z.-C. Zou (NJU), X. H. Tang (THU), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260605a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 44847) at 2026-06-05T09:31:00 (UTC). Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-06T10:39:36(UTC), ~25 hours after the WXT detection. The exposure time of the observation is around 6 ks. The on-ground analysis of the FXT data found an uncatalogued source within the error circle of WXT at R.A. = 273.298 deg, DEC = -40.3945 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic) . The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.03 x 10^21 cm^-2, and a photon index of 3.3 (-0.6, +0.5). The derived average unabsorbed 0.5-10 keV flux is 1.1 (-0.4, +0.9) ×10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42999] GRB 260607A: TRT optical observations
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44866 SUBJECT: GRB 260607A: TRT optical observations DATE: 26/06/08 10:34:45 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, L.B. He, D. Xu (NAOC), S.Y. Fu (HUST) report: We observed the optical counterpart candidate, AT2026ong, (Gompertz et. al., GCN 44864) of GRB 260607A detected by Fermi GBM (Fermi GBM Team, GCN 44855), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Fresno, California, U.S.A (SRO). A series of frames in the R-band were obtained. AT2026ong is clearly detected in our stacked image with a brightness of R = 19.2 +/- 0.2 at a median time of ~20.5 hrs post-trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. There is no decay between the GOTO and TRT observations. The previously reported potential host galaxy of AT2026ong (Gompertz et. al., GCN 44864) has a redshift of z ~ 0.126 from the [REGALADE](https://vizier.cds.unistra.fr/viz-bin/VizieR-3?-source=J/A%2bA/706/A284/regalade&-out.add=.) catalog (Tranin et al., 2026). View this GCN Circular online at https://gcn.nasa.gov/circulars/44866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42998] GRB 260604C: GRANDMA further observations
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44865 SUBJECT: GRB 260604C: GRANDMA further observations DATE: 26/06/08 09:38:41 GMT FROM: antier(a)ijclab.in2p3.fr O. Burkhonov (UBAI), M. Pillas (IAP), T. Leandro de Almeida (LNA), E. Elhosseiny (NRIAG), N. Kochiashvili (AbAO), L. Chen (TSU), A. Simon (TShNU of Kyiv), S. Antier (IJCLAB), M. Coughlin (UMN), S. Ehgamberdiev (UBAI), Y. Rajabov (UBAI), Y. Tillayev (UBAI), N. Sasaki (UEA,LNA), R. Inasaridze (AbAO), V. Zhuzhunadze (AbAO), A. Takey (NRIAG), W. Corradi (LNA), I. Abdusamatjan (TNOT) on behalf of GRANDMA: We conducted further follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with GRANDMA up to now. We observed a possible re-brightening in r, i, and R thanks to further observations from Two-meter Twin Telescope (TTT) sited at the Teide Observatory, UBAI-AZT-22 at Madainak Observatory, AbAO-T1.5m at Abastumani Observatory, KAO-1.88m at Kottamia Astronomical Observatory, and OPD-1.6m at Observatório do Pico dos Dias (Sasaki et al GCN 44857). This is shown in the public site group of the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260604_202037. To access, one simply needs to create an account using your ORCID id. Our measurements are aligned with Mondy's report (Pankov GCN 44862). The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (kilonovacatcher.in2p3.fr). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io). The TTT Observing Time Rights (DTO) used were provided by Light Bridges, SL. View this GCN Circular online at https://gcn.nasa.gov/circulars/44865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42997] GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44864 SUBJECT: GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong DATE: 26/06/08 09:15:55 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, M. Shrestha, R. Starling, A. Kumar, G. Ramsay, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, D. O'Neill and M. Pursiainen report 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 short GRB 260607A (Fermi GBM Team, GCN 44855). Targeted observations from GOTO-N covering the localisation area began at 2026-06-07 23:38:04 UT, (+10.81h post trigger) and continued through to 2026-06-08 03:49:33 UT (+15.0h post trigger). 260 images were taken, across 11 unique pointings, covering 417.3 sq. deg within the 90% localisation contour. ~82.7% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.5 mag. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. We identify one candidate optical counterpart contained within the 90% probability contour: +--------------------------------------------------------------------------+ | Internal name | IAU name | RA (J2000) | dec (J2000) | AB mag | +--------------------------------------------------------------------------+ | GOTO26fqf | AT2026ong | 314.468601 | 34.277287 | 19.54 ± 0.10 | +--------------------------------------------------------------------------+ We find no evidence of this source prior to the GRB trigger time in the previous GOTO epoch, taken at 04:13:23 UT on 2026-06-07 (t0 - 8.6h) to a 3-sigma limiting magnitude of L > 20.1 (AB). We also find no evidence for the source prior to the GRB in the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021). Its position is on the 63% probability contour of the GBM localisation map. GOTO26fqf / AT2026ong was detected in 3 epochs with magnitudes of L = 19.54 ± 0.10 (t0 + 12.1h), L = 19.83 ± 0.14 (t0 + 13.4h) and L = 19.84 ± 0.14 (t0 + 14.7h), which is consistent with a power-law temporal decay with an index of t^[-1.60 ± 0.64]. However, we caution that epochs 2 and 3 are consistent with no evolution. The candidate counterpart is spatially coincident with an extended object in PanSTARRS archival imaging, which we suggest is the host galaxy of the unidentified transient. We are unable to robustly relate GOTO26fqf / AT2026ong to GRB 260607A based on available observations but further follow-up, especially spectroscopic classification, is encouraged. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are 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/44864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42996] GRB 260604A: SVOM/GRM detection
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44863 SUBJECT: GRB 260604A: SVOM/GRM detection DATE: 26/06/08 09:07:17 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by a burst GRB 260604A at 2026-06-04T02:24:27.200 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44812). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of multiple pulses with a T90 of 4.0 +4.2/-2.2 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260604A.png In addition, the position of this burst, according to Fermi/GBM localization (RA = 60.4 deg, Dec = -12.8 deg, Err = 9.8 deg, Fermi GBM Team, GCN #44812), is located at about 71 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0+0 to T0+4 s is fitted by a power law function. The power law index is -1.69 +0.12/-0.11. The event fluence (10-1000 keV) in this time interval is (1.01 +0.17/-0.16)E-06 erg/cm^2. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Zheng-Hang Yu (IHEP) (zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42995] GRB 260604C: Mondy optical observations: evidence of a possible brightening
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44862 SUBJECT: GRB 260604C: Mondy optical observations: evidence of a possible brightening DATE: 26/06/08 09:03:44 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Moskvitin (SAO RAS), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260604C (The Fermi GBM team, GCN 44822; Neights & Meegan, GCN 44831; Gotz et al., GCN 44823) with the AZT-33IK 1.6-m telescope of the Sayan Solar Observatory (Mondy). The observations were conducted starting on 2026-06-07 16:34 UT, i.e. ~2.86 days since GRB. We aquired 30x120 sec exposures in the R-band using a CMOS-photometer. The optical afterglow (Lipunov, GCN 44827; Konno et al., GCN 44828; GCN 44836; Zhu et al., GCN 44832; Becerra et al., GCN 44834; Hellot et al., GCN 44835; Konno et al., GCN 44836; Gompertz et al., GCNs 44837, 44843; Chen et al., GCN 44851; Moskvitin et al., GCN 44852; Sasaki et al., GCN 44857; Pankov et al., GCN 44858) is clearly detected in the co-add image and displays an evidence of a brightening in comparison with previous epochs of observations (Moskvitin et al., GCN 44852; Sasaki et al., GCN 44857; Pankov et al., GCN 44858). The observations details and preliminary photometry are summarized below: Date UTstart t-T0 Exp. Filter Mag Err. UL (mid,d) (n*s) (3-sigma) 2026-06-07 16:34:49 2.86396 28x120 R 21.18 0.06 23.2 The photometry is based on nearby SDSS stars (R-magnitudes were obtained using Lupton 2005 transformation equations) as in Moskvitin et al., GCN 44852, and was not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42994] GRB 260607B: Fermi GBM Observation
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44861 SUBJECT: GRB 260607B: Fermi GBM Observation DATE: 26/06/08 02:49:06 GMT FROM: eliza.neights(a)gmail.com E. Neights (GWU, NASA GSFC) and E. Palafox (INAOE-Mexico) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:19:28.70 UT on 07 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260607B (trigger 802531173/260607555), which was also detected by Fermi LAT (Holzmann Airasca et al. 2026, GCN 44860). The Fermi GBM on-ground location is consistent with the Fermi LAT position. The angle from the Fermi LAT boresight is 72 degrees. The GBM light curve consists of multiple emission episodes, with a duration (T90) of about 47 s (50-300 keV). The time-averaged spectrum from T0+2.9 to T0+57.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.92 +/- 0.004 and the cutoff energy, parameterized as Epeak, is 728 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (2.999 +/- 0.006)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+53 s in the 10-1000 keV band is 66.9 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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