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

[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…

1 0

[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…

1 0

[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…

1 0

[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…

1 0

[vsnet-grb-info 42993] GRB 260607B: Fermi-LAT detection
by GCN Circulars 08 Jun '26

08 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44860 SUBJECT: GRB 260607B: Fermi-LAT detection DATE: 26/06/08 00:59:52 GMT FROM: N. Di Lalla at Stanford University <niccolo.dilalla(a)stanford.edu> A. Holzmann Airasca (UniTrento and INFN Bari), R. Gupta (NASA/GSFC) and N. Di Lalla (Stanford University) report on behalf of the Fermi-LAT team: At 13:19:28.70 UT on June 7th, 2026 Fermi-LAT detected high-energy emission from GRB 260607B, which was also detected by Fermi-GBM (trigger 802531173/260607555, GCN #44859). The best LAT on-ground location is found to be RA, Dec = 54.68, 30.45 (J2000) with an error radius of 0.40 deg (90 % containment, statistical error only). This was 72 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 - 1.2 ks after the GBM trigger is (2.22 ± 0.50)E-5 ph/cm2/s. The estimated photon index above 100 MeV is -1.98 ± 0.15. The highest energy photon has an energy of 4.7 GeV and occurs at 120 s after trigger time. The Fermi-LAT point of contact for this burst is Niccolò Di Lalla (niccolo.dilalla(a)stanford.edu) 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/44860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42992] GRB 260607B: Fermi GBM Final Localization Correction
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44859 SUBJECT: GRB 260607B: Fermi GBM Final Localization Correction DATE: 26/06/07 21:01:33 GMT FROM: Eva M. Palafox at INAOE <eva.palafox(a)gmail.com> The Fermi GBM team reports the detection of a likely LONG GRB "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). This trigger was initially classified as Distant Particles by the flight software, but is in fact a GRB. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 55.11, Dec = 26.90 (J2000 degrees, equivalent to J2000 +03h 40m, +26d 54'), with a statistical uncertainty of 1.00 degree. The angle from the Fermi LAT boresight is 68 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607555/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607555/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607555/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42991] GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44858 SUBJECT: GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow DATE: 26/06/07 19:31:45 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Pozanenko (IKI), A. Novichonok (KIAM), A. Moskvitin (SAO RAS), I. Nikolenko (INASAN), 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 Zeiss-1000 1-m telescope of the Simeiz Observatory (mnt. Koshka) of INASAN. The observations were conducted on 2026-06-05 and 2026-06-06 epochs using a CCD-photometer and the R-filter. 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) is clearly detected in the co-add images obtained on both epochs. The observations details and preliminary photometry are summarized below: Date UTstart t-T0 Exp. Filter Mag Err. UL (mid,d) (n*s) (3-sigma) 2026-06-05 21:31:13 1.07291 26x150 R 21.35 0.14 22.4 2026-06-06 20:09:21 2.03341 46x150 R 21.53 0.19 22.3 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/44858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42990] GRB 260604C: OPD1.6m - GRANDMA observations - detection
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44857 SUBJECT: GRB 260604C: OPD1.6m - GRANDMA observations - detection DATE: 26/06/07 13:35:13 GMT FROM: Nelio Sasaki at NEPA-UEA <nsasaki(a)uea.edu.br> Nélio Sasaki (UEA-Parintins), Wagner Corradi (LNA), Leandro de Almeida (LNA), Felipe Navarete (LNA), S. Antier (OCA/IJCLAB), I. Tosta e Melo (IFN), A. Simon (TshNU of Kyiv), L. Chen (TSU), M. Coughlin (UMN) and P. Hello (IJCLAB) on behalf of Observatório do Pico dos Dias (OPD/LNA/Brazil) and the GRANDMA collaboration, report follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823, Chen et al., GCN 44851; Moskvitin et al., GCN 44852) performing photometry of the GRB260604C source with SPARC4 in the Sloan bands (g,r,i,z), using exposures of 40 × 180 s in (g), 120 × 60 s in (r), 120 × 60 s in (i), and 120 × 60 s in (z). The observations began on 2026-06-07T00:18:36.036 UTC, corresponding to JD 2461198.512917. The recentered position of the source is: RA = 14:57:49.54, Dec = +28:49:03.96 The measured magnitudes of the target are: Filter | Mag (AB) g | 22.0938 ± 0.0008 (Magnitude limit: 24.6925) r | 21.7162 ± 0.0005 (Magnitude limit: 23.9245) i | 21.5773 ± 0.0008 (Magnitude limit: 25.1456) z | 21.4418 ± 0.0006 (Magnitude limit: 23.8440) Photometric calibration was performed using Gaia DR3 field stars. For each comparison star, the Gaia magnitude (G) and color (G_BP-G_RP) were transformed to Sloan-type magnitudes (g,r,i,z). The photometric zero point in each filter was then obtained from the difference between the transformed magnitudes from the catalog and the instrumental magnitudes of the comparison stars, and applied to the instrumental magnitude of the target. The transformations in (g,r,i) follow the Gaia-SDSS color relationships of Evans et al. (2018), while the magnitude in (z) was estimated using the (G-g) versus (g-z) relationship of Jordi et al. (2010). The Gaia DR3 catalog is from Gaia Collaboration et al. / Vallenari et al. (2023). 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 by Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io) View this GCN Circular online at https://gcn.nasa.gov/circulars/44857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42989] GRB 260607A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44856 SUBJECT: GRB 260607A: Fermi GBM Final Real-time Localization DATE: 26/06/07 13:01:39 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 SHORT GRB At 12:49:18 UT on 7 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260607A (trigger 802529363.702736 / 260607534). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 304.2, Dec = 36.5 (J2000 degrees, equivalent to J2000 20h 16m, 36d 30'), with a statistical uncertainty of 7.3 degrees. The angle from the Fermi LAT boresight is 57.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42988] GRB 260607A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44856 SUBJECT: GRB 260607A: Fermi GBM Final Real-time Localization DATE: 26/06/07 13:01:39 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 SHORT GRB At 12:49:18 UT on 7 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260607A (trigger 802529363.702736 / 260607534). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 304.2, Dec = 36.5 (J2000 degrees, equivalent to J2000 20h 16m, 36d 30'), with a statistical uncertainty of 7.3 degrees. The angle from the Fermi LAT boresight is 57.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260607534/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0