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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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[vsnet-grb-info 42983] GRB 260604C: GRANDMA observations
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44851 SUBJECT: GRB 260604C: GRANDMA observations DATE: 26/06/06 17:16:35 GMT FROM: antier(a)ijclab.in2p3.fr L. Chen (TSU), N. Sasaki (UEA,LNA), A. Simon (TShNU of Kyiv), S. Antier (IJCLAB), M. Coughlin (UMN) O. Burkhonov (UBAI), S. Ehgamberdiev (UBAI), Y. Rajabov (UBAI), Y. Tillayev (UBAI), R. Inasaridze (AbAO), N. Kochiashvili (AbAO), V. Zhuzhunadze (AbAO), A. Klotz (IRAP), P. Put (NARIT), K. Noysena (NARIT), A. Manasanun (NARIT), M. Freeberg (KNC), E. Elhosseiny (NRIAG), A. Takey (NRIAG), M. Pillas (IAP), W. Corradi (LNA), T. Leandro de Almeida (LNA), I. Abdusamatjan (TNOT) on behalf of GRANDMA: We conducted follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with GRANDMA from 0.05 h post T0 (MJD 61195.84859954) up to now. To do this, we have collected data from KNC (Hellot et al., GCN 44835), TAROT/TCH, UBAI-NT60, UBAI-AZT22, AbAO-T70, KAO-1.8m, TRT-SRO, OPD-60, TTT and NOWT. GRB 260604C optical afterglow (reported by Lipunov et al., GCN 44827) is detected at several epochs and a subset of the photometry corrected for Galactic extinction is reported 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 in agreement with Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; GCN 44835; Gompertz et al., 44843,Saccardi et al. 44844. 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) View this GCN Circular online at https://gcn.nasa.gov/circulars/44851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42982] GRB 260604B: SVOM/GRM detection
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44850 SUBJECT: GRB 260604B: SVOM/GRM detection DATE: 26/06/06 14:28:23 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, 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 detected GRB 260604B during the routine ground search at 2026-06-04T08:45:56.000 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44818). 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 17 +9/-5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260604B.png In addition, the position of this burst, according to Fermi/GBM localization (RA = 173.4, Dec = -19.9, Fermi GBM Team, GCN #44818), is located at about 82 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-15 to T0+25 s is fitted by a power law function. The power law index is -1.67 +0.10/-0.11. The event fluence (10-1000 keV) in this time interval is (3.8 +0.8/-0.8)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: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42981] GRB 260605A: Insight-HXMT/HE detection
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44849 SUBJECT: GRB 260605A: Insight-HXMT/HE detection DATE: 26/06/06 14:02:12 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-06-05T01:04:27.850 (T0), Insight-HXMT/HE detected a long burst, GRB 260605A, which is also detected by SVOM/GRM. The Insight-HXMT/HE light curve mainly consists of a single pulse with a duration (T90) of 11.0 +2.5/-1.0 s. The 1s peak rate, measured from T0+1.75 s, is 6386 cnts/sec. Insight-HXMT/HE detected a total of 22324 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260605A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE 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://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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