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

[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…

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[vsnet-grb-info 42992] GRB 260607B: Fermi GBM Final Localization Correction
by GCN Circulars 08 Jun '26

08 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…

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[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…

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[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…

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[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…

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[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…

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[vsnet-grb-info 42987] GRB 260607A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44855 SUBJECT: GRB 260607A: Fermi GBM Final Real-time Localization DATE: 26/06/07 13:00:13 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/44855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42986] GRB 260604C: GECAM-B observation
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44854 SUBJECT: GRB 260604C: GECAM-B observation DATE: 26/06/07 12:57:24 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260604C, at 2026-06-04T20:18:44.600 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44822), and SVOM/ECLAIRs (D. Gotz et.al., GCN#44823). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 7 +/-0.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260604C.png In addition, the position of this burst, is determined by SVOM/ECLAIRs (RA=224.3461 , DEC=28.6558, with a 90% confidence level raiuds of 9.6 arcmins , D.Gotz et.al., GCN #43647). With this localization, the time-averaged spectrum from T0-0.5 to T0+7.5 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.41 +0.12/-0.09 and the cutoff energy, parameterized as Epeak, is 759 +342/-210 keV. The event fluence (10-1000keV) in this time interval is (2.88 +0.086/-0.11)E-05 erg/cm^2. The 'Amati' relation diagram of GRB 260604C is shown at: https://www.bursthub.cn//admin/static/gecambgrb260604C_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/44854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42985] GRB 260604C: 6 GHz VLA observations
by GCN Circulars 07 Jun '26

07 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44853 SUBJECT: GRB 260604C: 6 GHz VLA observations DATE: 26/06/07 10:22:39 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> R. Ricci, M. Yadav, E. Troja (U Rome) report: We observed the field of GRB 260604C which triggered Fermi-GBM (Fermi-GBM team, GCN 44822) and SVOM (Gotz et al., GCN 44823) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz on June 04th 2026 (38 hours after the trigger). Data were calibrated and imaged using standard procedures in CASA (v6.6.1). 1331+305 (3C286) was used for flux density and bandpass calibration and J1513+2338 was used for complex gain calibration. No radio source was detected at the optical transient position (Lipunov et al., GCN 44827) down to a preliminary 3-sigma upper limit of ~24 uJy/beam. Further observations are planned. We thank the VLA staff for executing the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42984] GRB 260504C: SAO RAS optical observations
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44852 SUBJECT: GRB 260504C: SAO RAS optical observations DATE: 26/06/06 20:42:04 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of long GRB 260604C discovered by Fermi (The Fermi GBM team, GCN 44822; Neights & Meegan, GCN 44831) and SVOM (Gotz et al., GCN 44823) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. We obtained 12 x 300 sec. images in Rc band on June 05, 22:25:58--23:33:55 UT. The OT (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; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843; Chen et al.б GCN 44851) is clearly detected in our stacked image with the following brightness: Date UTstart t-T0 Exp. Filter Mag +/- Err. UL (mid,d) (n*s) (3-sigma) 2026.06.05T22:25:58 1.11195 12*300 Rc 21.65 +/- 0.07 23.4 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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