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[vsnet-grb-info 43251] GRB 260624A: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Jun '26

24 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45036 SUBJECT: GRB 260624A: Fermi GBM Final Real-time Localization DATE: 26/06/24 16:06:42 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 15:54:14 UT on 24 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260624A (trigger 804009259.148196 / 260624663). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 54.1, Dec = -21.0 (J2000 degrees, equivalent to J2000 03h 36m, -21d 00'), with a statistical uncertainty of 4.4 degrees. The angle from the Fermi LAT boresight is 73.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260624663/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260624663/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260624663/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45036. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43250] EP260623a:refined analysis of the EP-WXT and EP-FXT observation
by GCN Circulars 24 Jun '26

24 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45035 SUBJECT: EP260623a:refined analysis of the EP-WXT and EP-FXT observation DATE: 26/06/24 09:06:30 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.T. Wang (YNAO, CAS), Y. L. Hua (PMO, CAS) and C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260623a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 45020) and followed by several optical telescopes (Li et al., GCN 45021; Angulo et al., GCN 45024; Brivio et al., GCN 45025; Jiang et al., GCN 45026; Li et al., GCN 45027; Jelinek et al., GCN 45029; Lee et al., GCN 45030; Saikia et al., GCN 45034) with the redshift confirmed at z=0.703 (Izzo et al., GCN 45022). The refined analysis of the WXT data shows that the event started at T0=2026-06-23T02:52:27Z (UTC) and lasted for 103 s before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5–4 keV spectrum can be fitted with an absorbed power-law model (tbabs*ztbabs*powerlaw) with a fixed Galactic hydrogen column density of 8.1 × 10^20 cm^-2 and a fixed redshift of z = 0.703. The best-fit photon index is 1.83 (-0.56/+0.63), and the intrinsic hydrogen column density is 2.25 (-0.97/+1.21) × 10^22 cm^-2. The derived average unabsorbed 0.5–4 keV flux is 3.17 (-0.74/+1.39) × 10^-9 erg/s/cm^2. The estimated peak flux is 1.0 × 10^-8 erg/s/cm^2, corresponding to a peak luminosity of 2.2 × 10^49 erg/s. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2026-06-23T02:56:08 (UTC), about 3.7 minutes after T0. The exposure time of this observation is 3211 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 328.2698, 12.7938 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT light curve displays two pulses structure lasting for around 210 s. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 8.1 × 10^20 cm^-2 and a photon index of 1.96 (-/+ 0.03), and the intrinsic hydrogen column density is 0.94 (-/+ 0.04) × 10^22 cm^-2. The derived average unabsorbed 0.5-10 keV flux is 7.33 (-/+ 0.10) × 10^-9 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/45035. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43249] EP260623a: WINTER J-band observations
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45034 SUBJECT: EP260623a: WINTER J-band observations DATE: 26/06/23 22:37:06 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Aditya Pawan Saikia (IITB), Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (NOIRLab), Benjamin Schneider (LAM), Robert Stein (UMD), Viraj Karambelkar (Columbia), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of EP260623a (Wang et al., GCN 45020) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2026-06-23T07:00:29 UTC in the J band (4.1 hr after the EP trigger), consisting of 30*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with MIRAR (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We detect a source at the optical counterpart location (Li et al., GCN 45021; Izzo et al., GCN 45022; Angulo et al., GCN 45024; Brivio et al., GCN 45025; Jiang et al., GCN 45026; Li et al., GCN 45027; Jelinek et al., GCN 45029; Lee et al., GCN 45030), with magnitude J = 17.9 ± 0.1 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/45034. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43248] GRB 260617A: Glowbug gamma-ray detection of a short burst
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45033 SUBJECT: GRB 260617A: Glowbug gamma-ray detection of a short burst DATE: 26/06/23 22:12:11 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260617A, which was also detected by Fermi/GBM (GCN 44969, 44972), Konus-Wind and Mars-Odyssey/HEND (GCN 44982, 44998), and CALET (GCN 44989). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-17 21:36:42.640 with a duration of 0.26 s and a total significance of about 27 sigma. The light curve comprises a multi-peaked emission similar to the CALET light curve (GCN 44989). The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/45033. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43247] IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45032 SUBJECT: IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/06/23 19:49:02 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(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-260622A (https:/.gov/circulars/45018) in a time range of 1000 seconds centered on the alert event time (2026-06-22 15:33:34.814 UTC to 2026-06-22 15:50:14.814 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-260622A. 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 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260622A 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 3e+02 GeV and 2e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-06-21 15:41:54.814 UTC to 2026-06-23 15:41:54.814 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 1.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260622A 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/45032. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43246] IPN triangulation of GRB 260605A
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45031 SUBJECT: IPN triangulation of GRB 260605A DATE: 26/06/23 17:47:50 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(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, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, C. Wang (IHEP), S. Xiong (IHEP), S. Zhang (IHEP), J. Wei (NAOC), and B. Cordier (CEA) on behalf of the SVOM-GRM team, C. Wang (IHEP), S. Xiong (IHEP), and S. Zhang (IHEP) on behalf of the Insight-HXMT team, E. Burns on behalf of the IPN, 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 long-duration GRB 260605A (Insight-HXMT/HE detection: Zao et al., GCN 44849) was detected by Insight (HXMT/HE), SVOM (GRM), Konus-Wind, and Mars-Odyssey (HEND) at about 3868 s UT (01:04:28). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: ------------------------------ RA(2000), deg Dec(2000), deg ------------------------------ Corners: 110.4929 +37.9757 110.4379 +38.1277 108.8194 +18.8592 108.8935 +19.0360 ------------------------------ The error box area is 3003 sq. arcmin, and its maximum dimension is 20.3 deg (the minimum one is 2.6 arcmin). The Sun distance was ~27 deg. This localization may be improved. A triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB260605_T03858/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density. View this GCN Circular online at https://gcn.nasa.gov/circulars/45031. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43245] EP260623a: Optical follow-up observations with Kinder
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45030 SUBJECT: EP260623a: Optical follow-up observations with Kinder DATE: 26/06/23 16:42:04 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> M.-H. Lee, A. Aryan, T.-W. Chen, W.-J. Hou (all NCU), A. K. H. Kong (NTHU), S. J. Smartt, J. Gillanders (both Oxford), S. Yang(HNAS), A. Sankar.K, K. N.-T. Ho, A. Dutta, Y.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, H.-Y. Hsiao, C.-S. Lin, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), K. W. Smith, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP260623a (Wang et al., GCN 45020) using the 1m LOT at the Lulin observatory, as part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first LOT epoch of observations in r-band started at 15:26 UTC on the 23rd of June 2026 (MJD 61214.6431), 12.53 hr after the EP-WXT detection. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. Next, we employed the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. In the difference image, the optical counterpart (Li et al., GCN 45021; Izzo et al., GCN 45022; Angulo et al., GCN 45024; Brivio et al., GCN 45025; Jiang et al., GCN 45026; Li et al., GCN 45027; and Jelinek et al., GCN 45029) was clearly detected. Moreover, we further used AutoPhOT to perform PSF photometry. The details of the observations and measured photometry (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61214.6431 | 12.53 | 300 * 6 | 20.74 +/- 0.07 | 1".97 | 1.91 The presented magnitudes are calibrated using the field stars from ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105). The reported magnitude is not corrected for an expected galactic extinction of A_r = 0.32 mag, in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/45030. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43244] EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45029 SUBJECT: EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay DATE: 26/06/23 14:29:58 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> Martin Jelinek, Jan Strobl and Filip Novotny (ASU CAS Ondrejov, CZ), Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ) report: The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically to the alert of EP260623a (Wang et al. GCN 45020), obtaining a series of unfiltered images starting at 02:59:17 UT, i.e. ~5 min post trigger. The observation consists of a set of 20 x 20 s exposures followed by a longer set of 120 x 60 s exposures. We clearly detect the optical counterpart reported by other telescopes (Li et al. GCN 45021; Izzo et al. GCN 45022; Angulo et al. GCN 45024; Brivio et al. GCN 45025; Jiang et al. GCN 45026). The FRAM observations cover the rise of the transient, its peak and the subsequent decay. The source peaked at ~T0+24 min at a brightness of r ~ 15.4, after which it decays with a power-law index alpha ~ 1.7, with a few rebrightenings. The photometry is calibrated against the Atlas-REFCAT2 catalogue (Tonry et al. 2018, ApJ, 867, 105) and is not corrected for Galactic extinction. Extrapolating the observed decay to T0+24h yields a predicted brightness of r ~ 22.0. View this GCN Circular online at https://gcn.nasa.gov/circulars/45029. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43243] GRB 260623A: Fermi GBM Final Real-time Localization
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45028 SUBJECT: GRB 260623A: Fermi GBM Final Real-time Localization DATE: 26/06/23 13:09:24 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 12:56:49 UT on 23 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260623A (trigger 803912214.021094 / 260623539). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 39.3, Dec = -10.4 (J2000 degrees, equivalent to J2000 02h 37m, -10d 24'), with a statistical uncertainty of 11.8 degrees. The angle from the Fermi LAT boresight is 88.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260623539/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260623539/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260623539/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45028. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43242] EP260623a: SVOM/VT optical observations
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45027 SUBJECT: EP260623a: SVOM/VT optical observations DATE: 26/06/23 12:19:38 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, J. R. Xu,, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations to the field of EP260623a triggered by Einstein Probe (Wang et al., GCN 45020). The observation started at 2026-06-10T04:10:37 UTC, about 1.28 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart (Li et al., GCN 45021; Angulo et al., GCN 45024; Brivio et al., GCN 45025; Jiang et al., GCN 45026) with the redshift of z=0.703 (Izzo et al., GCN 45022) was clearly detected by VT in both channels. The following measurements are in the AB magnitude without correction for Galactic extinction: Mid time | Band | Exposure Time | Brightness 1.283 h VT_B 50 s 17.00 +/- 0.04 mag 1.283 h VT_R 50 s 16.34 +/- 0.04 mag 3.191 h VT_B 50 s 18.59 +/- 0.07 mag 3.191 h VT_R 50 s 17.85 +/- 0.05 mag 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/45027. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43241] EP260623a: TRT optical observations
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45026 SUBJECT: EP260623a: TRT optical observations DATE: 26/06/23 10:40:56 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang, X. Liu (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan, K. Noysena (NARIT), L.B. He, Z.P. Zhu, J. An, Z. Fan, W.X. Li, N.C. Sun, D. Xu (NAOC), S.Y. Fu (HUST) report: We observed the field of EP260623a detected by EP (Wang et al., GCN 45020) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 04:32:21.6 UTC on 2026-06-23, i.e., 1.638 hrs after the EP trigger, and a series of frames were obtained in Sloan r-band. The optical counterpart (Li et al., GCN 45021; Izzo et al., GCN 45022; Angulo et al., GCN 45024; Brivio et al., GCN 45025) is clearly detected in our r-band images, with r = 17.13 +/- 0.02 at 1.767 hrs post-burst, calibrated with Panstarrs DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45026. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43240] EP260623a: REM optical/NIR afterglow detection
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45025 SUBJECT: EP260623a: REM optical/NIR afterglow detection DATE: 26/06/23 10:05:07 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), L. Izzo (INAF-OACN and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), A. Melandri (INAF-OAR) report on behalf of the REM team: We observed the field of EP260623a, detected by EP/WXT (Wang et al., GCN 45020) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried out in the g, r, i, z, K bands, started on 2026-06-23 at 03:57:45 UT (i.e. 1.1 hr after the burst) and lasted for about 1 hr. From preliminary photometry, we detect the optical/NIR counterpart (Li et al., GCN 45021; Izzo et al., GCN 45022; Angulo et al., GCN 45024) with the following magnitudes: r = 16.35 +/- 0.04 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 1.1 hr after the trigger; K = 13.51 +/- 0.17 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 1.1 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/45025. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43239] EP 260323a: COLIBRÍ optical observations
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45024 SUBJECT: EP 260323a: COLIBRÍ optical observations DATE: 26/06/23 07:02:10 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Camila Angulo (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), 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 EP 260623a (Wang et al., GCN Circ. 45020) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-23T06:23:26 to 06:37:31 UTC (from 3.49 to 3.69 hours after the trigger) and obtained 4 minutes of exposure in the g, r, i, z, filters and 8 minutes in the y filter. 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. We detected the optical counterpart reported by Las Cumbres (Li et al., GCN Circ. 45021), at preliminary magnitudes of: g = 18.73 +/- 0.04 r = 18.30 +/- 0.01 i = 18.00 +/- 0.01 z = 17.78 +/- 0.03 y = 17.55 +/- 0.03 Our detection in all bands suggests that this is a low-redshift event. Spectroscopic observations are encouraged. We also note that the source is located near the southern edge of the Sh 2-113 (the Flying Dragon Nebula), which may contribute to the moderate extinction observed at its position. 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/45024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43238] GRB 260616B/EP260616a: Insight-HXMT/HE detection
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45023 SUBJECT: GRB 260616B/EP260616a: Insight-HXMT/HE detection DATE: 26/06/23 06:06:51 GMT FROM: yzh807926(a)163.com GRB 260616B/EP260616a: Insight-HXMT/HE detection Zheng-Hang Yu, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-06-16T07:05:26.950 (T0), Insight-HXMT/HE detected GRB 260616B/EP260616a, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44953), AstroSat CZTI (A. Arya et al., GCN #44997) and SVOM/GRM (Yu et al., GCN #45011). The Insight-HXMT/HE light curve mainly consists of two pulses with a T90 of 11.6 +1.4/-0.3 s. The 1 s peak rate, measured from T0-0.25 s, is 2154 cnts/sec. Insight-HXMT/HE detected a total of 8808 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260616B.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the normal gain mode with the energy range of about 6-900 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/45023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43237] EP260623a: OSIRIS+/GTC redshift z = 0.703
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45022 SUBJECT: EP260623a: OSIRIS+/GTC redshift z = 0.703 DATE: 26/06/23 05:47:48 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> L. Izzo (INAF/OACN and DARK/NBI), A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), S. Geier (GTC), C. C. Thoene (AbAO), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), G. Lombardi (GTC), A. Martin-Carrillo (UCD), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), F. Pérez Toledo (GTC) and A. Pérez (GTC) report: We observed the optical counterpart (Li et al. GCN 45021) of EP260623a (Wang et al, GCN 45020) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In the 10-s acquisition image (beginning on 2026-06-23 at 04:44:12 UT, that is 1.83 hr after trigger), the optical afterglow is well detected with a magnitude 17.01 ± 0.05 (AB), calibrated against nearby LS objects, and not corrected for Galactic extinction. A total of 2 spectra of 600 s were secured, starting on 2026-06-23 at 04:49:58 UT (1.93 hr after EP trigger), using grism R1000B. Continuum is visible over the wavelength range 3615-7800 AA. A number of metal absorption features are detected, which we interpret as due to FeII, MnII, MgII, MgI, as well as multiple FeII fine structure transitions all at a common redshift z = 0.703, which we suggest to be the redshift of EP 260623a. This work has used the GRBspec database at http://grbspec.eu (de Ugarte Postigo et al. 2014, doi:10.1117/12.2055774). View this GCN Circular online at https://gcn.nasa.gov/circulars/45022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43236] EP260623a: Las Cumbres discovery of the optical counterpart
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45021 SUBJECT: EP260623a: Las Cumbres discovery of the optical counterpart DATE: 26/06/23 04:16:44 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcav, Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP260623a with a Las Cumbres 1m telescope at Teide Observatory, Tenerife, 8 mins after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w-band. We find an uncataloged source at RA=328.2698, Dec=12.7939 within the EP-FXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 61214.12687 Mag 16.54 +- 0.01 MJD 61214.13064 Mag 15.62 +- 0.01 This target brightened by ~0.9 mag within 6 minutes. The presented magnitudes are calibrated with Pan-STARRS sources in the field and not corrected for Galactic extinction. Additional follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/45021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43235] EP260623a: Einstein Probe detection of an X-ray transient
by GCN Circulars 23 Jun '26

23 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45020 SUBJECT: EP260623a: Einstein Probe detection of an X-ray transient DATE: 26/06/23 03:52:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B. T. Wang (YNAO, CAS), Y. L. Hua (PMO, CAS) and C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260623a. The transient triggered EP-WXT (ID: 01709272000) at 2026-06-23T02:54:05 (UTC). The WXT position of the source is R.A. = 328.262 deg, DEC = 12.813 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 328.2725 deg, DEC = 12.7946 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/45020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43234] GRB 260614B: EP-FXT follow-up observation
by GCN Circulars 22 Jun '26

22 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45019 SUBJECT: GRB 260614B: EP-FXT follow-up observation DATE: 26/06/22 22:10:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Pillas (IAP), A. Saccardi (CEA/Irfu), Ziming Wang (PKU), report on behalf of the SVOM and EP collaborations: EP-FXT performed a follow-up observation of GRB 260614B detected by SVOM/ECLAIRs (Godet et al., GCN 44938). The follow-up observation started on 2026-06-15 at 15:05:04 (UTC), about 25.3 hr after the SVOM trigger, with a total exposure time of 4 ks. On-ground analysis of the FXT data found an uncatalogued source within the ECLAIRs and MXT error circles at R.A., Dec. = 353.9080, -54.1164 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). This position is consistent with the optical counterpart (Palmerio et al., GCN 44939; Li et al., GCN 44943). The derived average unabsorbed flux is (1.64 +/- 0.25) x 10^(-13) erg/s/cm^2 (0.5-10 keV; 1-sigma uncertainty). 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/45019. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43233] IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 22 Jun '26

22 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45018 SUBJECT: IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 26/06/22 19:24:32 GMT FROM: janeth.phd(a)gmail.com The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 26-06-22 at 15:41:54.81 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.8158 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/142752_1835003.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 26-06-22 Time: 15:41:54.81 UT RA: 173.36 (+0.5/-0.52 deg 90% PSF containment) J2000 Dec: 1.34 (+0.58/-0.58 deg 90% PSF containment) J2000 As announced in GCN Circular 43419 (https://gcn.nasa.gov/circulars/43419) IceCube alert notices for high-energy track alerts are now also streamed via Kafka. IceCube Gold/Bronze track alerts are available on the Kafka topic 'gcn.notices.icecube.gold_bronze_track_alerts'. The probability distribution of the true neutrino direction, allowing the extraction of precise 90% containment regions around the best-fit direction, is now available for revised reconstruction of high-energy track alerts. The corresponding sky map is distributed as a FITS file and follows the explicit naming convention IceCube-YYMMDDX, where YYMMDD indicates the date of the event and X is a letter distinguishing multiple alerts on the same day. The download link is provided through the GCN schema distributed via Kafka. Detailed documentation describing the alert distribution, schemas, and probability maps is available at: https://gcn.nasa.gov/missions/icecube. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of this event. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/45018. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43232] GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
by GCN Circulars 22 Jun '26

22 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45017 SUBJECT: GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search DATE: 26/06/22 14:33:28 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet (IRAP), report on behalf of the SVOM/ECLAIRs team: The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 260618C, starting at 2026-06-18T04:02:26.6 UTC (trigger time T0), through an on-ground search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several energy ranges and timescales. The best detection is obtained by the Image Trigger with a signal-to-noise ratio of 8.6 within 4-20 keV over a time window of 7 seconds starting at T0-7s. The burst that triggered ECLAIRs onground shows a single peak structure. The burst duration is T90 = 6 +/-1 s in the 4-20 keV energy band. The localization of the source is RA, Dec = 294.933, -65.710 degrees: RA (J2000) = 19h39m43.9s Dec (J2000) = -65d42m36.0s with a 90% C.L. radius of 10.7 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright catalogued X-ray sources are found in the error box. The time-averaged spectrum from T0-7 s to T0 in the 5-50 keV energy range is best fitted by a blackbody model with kT = 3.65 +0.47/-0.42 keV.. With this model, the 4-120 keV fluence is (8.3 +0.7/-2.4) e-8 erg/cm^2 and the 4-120 keV photon flux is 0.65 +0.04 /-0.15 ph/cm^2/s. Both broken power-law and power-law with an exponential cutoff models can equally fit the spectrum, however, their parameters can not be constrained due to the faintness of this burst. This event is very soft and if it is a GRB, then it should be probably classified as an X-Ray Flash. All the quoted errors are at the 68% confidence level. A SVOM ToO observation has been requested to follow-up this trigger with both MXT and VT instruments. The results of these observations will be reported later in future circulars. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45017. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43231] GRB 260619A: NOT optical observations
by GCN Circulars 21 Jun '26

21 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45015 SUBJECT: GRB 260619A: NOT optical observations DATE: 26/06/20 13:36:17 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), G. Corcoran (UCD), B. Schneider (LAM), report on behalf of a larger collaboration: We observed the optical afterglow (Ducoin et al., GCN 44999; Li et al., GCN 45003; He et al., GCN 45008) of the SVOM GRB 260619A (Goto et al., GCN 44985) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the SDSS i band and consisted of 4x300 s exposures. The optical afterglow is detected with an AB magnitude i = 22.26 +- 0.08 at the mean epoch Jun 20.207 UT (1.114 days after trigger), calibrated against nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction. We note that our measurement indicates little evolution of the counterpart brightness compared to previously reported flux values. We encourage further follow-up to better understand the nature of this object. View this GCN Circular online at https://gcn.nasa.gov/circulars/45015. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43230] EP260618a: Liverpool Telescope optical observations
by GCN Circulars 21 Jun '26

21 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45016 SUBJECT: EP260618a: Liverpool Telescope optical observations DATE: 26/06/20 14:22:19 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of EP260618a (Yang et al., GCN 44978; Jiang et al., GCN 44991) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x150s exposures in SDSS griz filters, starting at 2026-06-19 02:32:19 UT, approximately 17.96 hours after EP trigger. Some z-band exposures had to be discarded prior to stacking. We detect a source in the images in all filters at the position reported by Becerra et al. (GCN 44988), also Malesani et al. (GCN 44990), Amram et al. (GCN 44994) and He et al. (GCN 45012). The photometry is: | MJD (mid) | T_mid-T_0 | Filter | Mag. (AB) | |---------------|-------------|-----------|---------------| | 61210.11078 | 18.08 h | g | 22.47 ± 0.24 | | 61210.12120 | 18.34 h | r | 22.03 ± 0.12 | | 61210.13221 | 18.59 h | i | 21.62 ± 0.11 | | 61210.14403 | 18.88 h | z | 21.48 ± 0.26 | The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45016. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43229] GRB 260618B: LCO optical observations
by GCN Circulars 21 Jun '26

21 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45014 SUBJECT: GRB 260618B: LCO optical observations DATE: 26/06/20 09:11:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y.Y. Shi (GXU), A. Saccardi (CEA/Irfu), S.J.Yin (GXU), C. Wu (NAOC), L.P. Xin (NAOC), D. Turpin(CEA/Irfu) report on behalf of the SVOM mission team: We observed the field of the GRB 260618B detected by Fermi-GBM (Fermi GBM team, GCN 44979; Veres et al. GCN 45010) and Fermi-LAT (Gupta et al., GCN 44983) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started on 2026-06-20 at 00:01:12 (about 31.1 hr after the trigger) and we obtained 5x200 s exposures in the SDSS r and 5x200 s exposures in the Pan-STARRS z filters. The optical counterpart (Li et al., GCN 45001) is detected in our images. We measure the following magnitudes calibrated against the DESI DR10 catalog, and not corrected for Galactic extinction: r = 20.49 +/- 0.06 AB (mid-time 31.25 hr after the trigger); z > 20.9 AB (3-sigma, mid-time 32.35 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/45014. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43228] EP260618a: JinShan optical observations
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45012 SUBJECT: EP260618a: JinShan optical observations DATE: 26/06/20 06:12:59 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, S.Q. Jiang, J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report: We observed the field of EP260618a detected by EP/WXT (Yang et al., GCN 44978; Jiang et al., GCN 44991), possibly associated with GRB 260618A (Fermi GBM Team, GCN 44973) using the JinShan 100C telescope located at Altay, Xinjiang, China. The previously reported optical counterpart (Becerra et al., GCN 44988; Malesani et al., GCN 44990; Amram et al., GCN 44994) is detected in our stacked images with a brightness of r ~ 21.4 mag at a median time of 1.429 days since the EP trigger, i.e. 1.504 days since the Fermi GBM trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43227] The EP-WXT trigger 01709271197 is likely a flaring star
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45013 SUBJECT: The EP-WXT trigger 01709271197 is likely a flaring star DATE: 26/06/20 06:51:55 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H. Jiang (NJU), Q.Y. WU, W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709271197 at the time of 2026-06-20T05:24:06, is likely a stellar flare associated with 2MASS J18430597-4058047. The estimated flux of the flare is around 1.0 x 10 ^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4.1 x 10^(31) erg/s. 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/45013. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43226] GRB 260616B/EP260616a: SVOM/GRM detection of a burst
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45011 SUBJECT: GRB 260616B/EP260616a: SVOM/GRM detection of a burst DATE: 26/06/20 04:00:46 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM), Olivier GODET, Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 260616B/EP260616a (SVOM trigger reference: sb26061603) at 2026-06-16T07:05:16.900 UTC (T0), which is also detected by Fermi/GBM (C. Malacaria et al., GCN #44953). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a main episode with two peaks a T90 of 13.30 +0.8/-0.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb2606016B.png In addition, the position of this burst, as determined by EP/WXT (RA= 256.059 deg, DEC= -32.305 deg, ERR=2.2 arcmin, GCN#44956), is located at about 67 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, and ECLAIRs was totally blocked by the Earth. Nevertheless, ECLAIRs detected this burst clearly over the 4-120 keV via atmospheric reflection. With this localization, the time-averaged spectrum from T0-2 to T0+14 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +/-0.04 and the cutoff energy, parameterized as Epeak, is 622 +80/-66 keV. The event fluence (10-1000 keV) in this time interval is (2.29 +/-0.06)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+9.8 to T0+10.8 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.90 +0.05/-0.06 and the cutoff energy, parameterized as Epeak, is 472 +52/-44 keV. The flux (10-1000 keV) in this time interval is (4.85 +/-0.17)E-06 erg/cm^2/s. The localization of GRB 260616B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616B_amati.png The localization of GRB 260616B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616B_yonetoku.png 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 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/45011. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43225] GRB 260618B: Fermi GBM Observation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45010 SUBJECT: GRB 260618B: Fermi GBM Observation DATE: 26/06/19 17:39:30 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:55:04.71 UT on 18 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618B (trigger 803494509/260618705), which was also detected by Fermi/LAT (Gupta et al., GCN 44983) and SVOM/VT (Li et al., GCN 45001). The Fermi GBM on-ground location is consistent with the LAT and the SVOM/VT position. The angle from the Fermi LAT boresight is 16 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0 to T0+10 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.42 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 1030 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.96 s in the 10-1000 keV band is 4.3 +/- 0.2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 1000 +/- 20 keV, alpha = -0.41 +/- 0.02 and beta = -3.2 +/- 0.2. 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/45010. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43224] IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45009 SUBJECT: IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/06/19 16:38:39 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(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-Cascade 260618A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/142737_24549075.amon) in a time range of 1000 seconds centered on the alert event time (2026-06-18 05:19:19.175 UTC to 2026-06-18 05:35:59.175 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-Cascade 260618A. 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, ranges from 1.4e-01 to 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-Cascade 260618A 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 8e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-06-17 05:27:39.175 UTC to 2026-06-19 05:27:39.175 UTC). In this case, we report a p-value of 0.48, 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, ranges from 1.6e-01 to 1.8e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-Cascade 260618A 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/45009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43223] GRB 260619A: TRT optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45008 SUBJECT: GRB 260619A: TRT optical counterpart confirmation DATE: 26/06/19 16:30:48 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC) report: We observed the field of GRB 260619A detected by SVOM/ECLAIRs (Goto et al., GCN 44985) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile (CTO). The previously reported optical counterpart (Ducoin et al., GCN 44999; Li et al., GCN 45003) is detected in our stacked images with a brightness of r~21.4 at a median time of 3.95 hrs post-trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45008. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43222] GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45007 SUBJECT: GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection DATE: 26/06/19 15:24:48 GMT FROM: marion.pillas(a)ligo.org A. Simon (TShNU of Kyiv), M. Mašek (FZU), N. Kochiashvili (AbAO), M. Pillas (IAP), D. Akl (NYUAD), R. Hanna (IJCLAB), P. Putsathan (KKU), Y. Rajabov (UBAI), S. Antier (IJCLAB), P. Hello (IJCLAB), M. Coughlin (UNM), S. Karpov (FZU), C. Douzet (IJCLAB), D. Rusanova (TShNU of Kyiv), V. Shynkarova (TShNU of Kyiv), A. Korosko (TShNU of Kyiv), O. Burkhonov (UBAI), S. Ehgamberdiev (UBAI), Y. Tillayev (UBAI), P. Put (NARIT), K. Noysena (NARIT), M. Tanasan (CMU/NARIT), D. Turpin (CEA-Saclay/Irfu), M. Freeberg (KNC), C. Limonta (OCA), A. Dupin (OCA), Q. André (OCA), M. Molham (NRIAG), E. Elhosseiny (NRIAG), A. Takey (NRIAG), T. Kvernadze (AbAO) on behalf of on GRANDMA collaboration: We continued our observations of the field of the Fermi Long GRB 260610B (Fermi GBM team, GCN 44901). The additional observations started on June 2026, 16 up to now. We still detect the optical afterglow using TTT-200cm, T150 at Abastumani Observatory, UBAI-AZT-22 at Madainak Observatory, AZT-8 at Lisnyky Observatory, KAO-1.88m at Kottamia Astronomical Observatory. We detect a re-brightening, which is consistent with other measurements reported in GCN 44955, GCN 44958, GCN 44959, GCN 44963, GCN 44993, 44999, 45003, 45004. A subset of the photometry corrected for Galactic extinction is reported in the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/2026owq. To access, one simply needs to create an account using your ORCID id. The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousins filters were calibrated using the Gaia DR3 Synphot catalog. 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/45007. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43221] GRB 260604B: 239Alferov CubeSat detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45006 SUBJECT: GRB 260604B: 239Alferov CubeSat detection DATE: 26/06/19 14:51:29 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> GRB 260604B: 239Alferov CubeSat detection D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report: The long-duration GRB 260604B (Fermi-GBM detection: The Fermi GBM team, GCN 44818; SVOM-GRM detection: Zhang et al., GCN 44850) was detected by 239Alferov 3U CubeSat at about 31555 s (08:45:55) UT. The burst was also detected by Konus-Wind in the waiting mode. The burst light curve, as measured by 239Alferov detector, shows a multi-peaked structure with a duration of ~8 s. The emission is seen up to ~500 keV. The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/239Alferov/260604B/ 239Alferov GRB detections are listed at: http://www.ioffe.ru/LEA/239Alferov/ 239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 0.5 s temporal resolution. The ground segment of the mission utilizes the SONIKS open ground station network. View this GCN Circular online at https://gcn.nasa.gov/circulars/45006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43220] GRB 260604A: 239Alferov CubeSat detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45005 SUBJECT: GRB 260604A: 239Alferov CubeSat detection DATE: 26/06/19 14:48:42 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report: The long-duration GRB 260604A (Fermi-GBM detection: The Fermi GBM team, GCN 44812; Glowbug detection: Cheung et al., GCN 44845; SVOM-GRM detection: Yu et al., GCN 44863) was detected by 239Alferov 3U CubeSat at about 8668 s (02:24:28) UT. The burst was also detected by Konus-Wind in the waiting mode. The burst light curve, as measured by 239Alferov detector, shows a single pulse with a duration of ~5 s. The emission is seen up to ~500 keV. The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/239Alferov/260604A/ 239Alferov GRB detections are listed at: http://www.ioffe.ru/LEA/239Alferov/ 239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 0.5 s temporal resolution. The ground segment of the mission utilizes the SONIKS open ground station network. View this GCN Circular online at https://gcn.nasa.gov/circulars/45005. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43219] GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45004 SUBJECT: GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening DATE: 26/06/19 14:42:59 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> G. Corcoran (UCD), A. Martin-Carrillo (UCD), L. Izzo (INAF/OAC and DARK/NBI), J. An (NAOC), D. B. Malesani (DAWN/NBI and Radboud), B. P. Gompertz (Birmingham), A. J. Levan (Radboud and Warwick), A. de Ugarte Postigo (LAM), report on behalf of the Stargate collaboration: We performed spectroscopic observations of GRB 260610B discovered by Fermi (Fermi GBM team, GCN 44901; Godwin & Meegan GCN 44931) and SVOM (Yu et al., GCN 44944), whose optical afterglow has recently experienced an optical rebrightening (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCNs 44910, 44955; 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; Angulo et al., GCN 44958; Moskvitin et al., GCN 44963; Pankov et al., GCN 44977; Gassert et al., GCN 44981; Gupta et al., GCN 44993). We used the ESO Very Large Telescope (VLT) UT1 (Antu) equipped with the FORS2 spectrograph with the 300V grism, covering the wavelength range 4400-8650 AA. The observation consisted of 4 exposures of 600 s each. The observation started at 00:41:19 UT on June 17 2026 (6.04 days after the GRB). In our acquisition image, we measured an AB magnitude r ~ 20 (calibrated against Pan-STARRS, not corrected for Galactic extinction). Based on the reported light curve, this seems to indicate that our observation occurred during the peak of this late flaring episode. The spectrum of the optical counterpart reveals a power-law continuum across the entire covered range suggesting that the observed recent activity is likely caused by late jet activity. Faint undulations are seen overimposed to the continuum, at a flux level consistent with the emergence of an early, still faint SN, but further observations will be required to conclude about its presence. Additionally, through the detection of the Ca II doublet in absorption and [O II] doublet in emission, we confirm the redshift reported by O’Neill et al. (GCN 44914), measuring z = 0.474. Further spectroscopic observations of the source are planned to monitor the possible emergence of the supernova. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Martina Baratella and Leo Rivas, for rapidly executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/45004. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43218] GRB 260619A: SVOM/VT optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45003 SUBJECT: GRB 260619A: SVOM/VT optical counterpart confirmation DATE: 26/06/19 14:30:00 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), Kuan Liu (GXU), Zhiyong Liu (GZNU) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations of GRB260619A triggered by SVOM/ECLAIRs (sb26061901, Goto et al., GCN 44985). The observation started at 2026-06-19T05:54:32 UTC, approximately 3.71 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate (Ducoin et al., GCN 44999) was detected in both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 6.13 h VT_B 14*70 s 22.56 +/- 0.15 mag 6.14 h VT_R 13*70 s 22.63 +/- 0.18 mag 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/45003. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43217] GRB 260618B: SVOM/VT optical candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45001 SUBJECT: GRB 260618B: SVOM/VT optical candidate DATE: 26/06/19 13:38:11 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations for GRB 260618B detected by Fermi-LAT (Gupta et al., GCN 44983) and Fermi-GBM (the Fermi GBM team, GCN 44979). The observation started at 2026-06-19T01:44:32 UTC, i.e., 8.83 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. An uncatalogued optical candidate was clearly detected in both channels compared with the Legacy Survey, with an angular separation of 8.7 arcminutes from the Fermi-LAT position (Gupta et al., GCN 44983). The position is at R.A., Dec. = 354.333559, -44.735518 degrees, equivalent to: R.A. (J2000) = 23:37:20.05 Dec. (J2000) = -44:44:07.87 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 10.53 h VT_B 48*70 s 20.8 +/-0.1 mag 10.53 h VT_R 41*70 s 20.9 +/-0.1 mag 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/45001. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43216] Fermi-LAT Gamma-ray Observations of IceCube-260610A
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45002 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260610A DATE: 26/06/19 14:05:43 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC260610A neutrino event (GCN 44899) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 26-06-10 at 20:02:41.03 UTC (T0) with J2000 position RA = 309.20 (+2.04, -2.06) deg, Decl. = 37.22 (+0.96/-0.93) deg 90% PSF containment. Two cataloged >100 MeV gamma-ray source are located within the 90% IC260610A localization error, at a distance of roughly 0.77 and 1.45 deg (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). These are the objects: 4FGL J2035.0+3632 associated with PSR J2034+3632. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month, this object is not significantly detected at gamma-rays. 4FGL J2030.0+3641 associated with PSR J2030+3641. Based on a preliminary analysis of the LAT data over the timescale of 1-day, this object is not significantly detected at gamma-rays. On a 1-month integration timescale prior to T0, it is detected significantly but the flux is in agreement with the average flux of the source reported in 4FGL-DR4. We conclude that the source is not in high state. We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC260610A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260610A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.7e-9 ph cm^-2 s^-1 for ~18-years (2008-08-04 / T0), <1.2e-08 (<2.6e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source the Fermi-LAT contact person is Leonard Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). 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/45002. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43215] GRB 260618B: SVOM/VT optical candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45000 SUBJECT: GRB 260618B: SVOM/VT optical candidate DATE: 26/06/19 13:04:05 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations for GRB 260618B detected by Fermi-LAT (Gupta et al., GCN 44983) and Fermi-GBM (the Fermi GBM team, GCN 44979). The observation started at 2026-06-19T01:44:32 UTC, i.e., 8.83 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. An uncatalogued optical candidate was clearly detected in both channels compared with the Legacy Survey, with an angular separation of 8.7 arcminutes from the Fermi-LAT position. The position is at R.A., Dec. = 240.862173, 50.563348 degrees, equivalent to: R.A. (J2000) = 16:03:26.92 Dec. (J2000) = +50:33:48.05 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 10.53 h VT_B 48*70 s 20.8 +/-0.1 mag 10.53 h VT_R 41*70 s 20.9 +/-0.1 mag 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/45000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43214] GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44999 SUBJECT: GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 26/06/19 13:01:35 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Hatsune Goto (RIKEN), Jun Yang (ZZU), Kuan Liu (GXU), Zhiyong Liu (GZNU) report: We imaged the field of the SVOM GRB 260619A (Goto et al., GCN Circ. 44985) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-06-19 09:49:05 to 11:11:49 UTC (from 7.62 to 9.01 hours after the trigger) and obtained 61 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ ASU pipeline and cross-analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect an uncatalogued source (revealed by image subtraction using Legacy Survey) consistent with the ECLAIRs 11.33 arcmin error circle (Goto et al., GCN Circ. 44985) at: RA(J2000) = 23:56:24.46 = 359.10192 degrees Dec(J2000) = -15:27:41.0 = -15.46140 degrees with an uncertainty of 0.5 arcsec. The preliminary unsubtracted magnitude derived for that source is: r = 22.13 +/- 0.05 z = 21.91 +/- 0.14 The lack of clear evidence for variability, prevents a firm confirmation that this source is the optical afterglow of GRB 260619A. 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/44999. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43213] Konus-Wind detection of GRB 260617A
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44998 SUBJECT: Konus-Wind detection of GRB 260617A DATE: 26/06/19 12:29:15 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short-duration GRB 260617A (Fermi-GBM detection: Fermi GBM team, GCN 44969; Godwin & Meegan, GCN 44972; IPN triangulation: Kozyrev et al., GCN 44982; CALET-GBM detection: Torii et al., GCN 44989) triggered Konus-Wind at T0=77808.934 s UT (21:36:48.934). The burst light curve shows a multi-peaked pulse, which starts at ~T0-64 ms and has a total duration of ~150 ms. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260617_T77808/ As observed by Konus-Wind, the burst had the total fluence of 1.28(-0.16,+0.19)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0-0.060 s, of 1.73(-0.36,+0.38)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Since the brightest peak of the burst light curve was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data. Modelling the KW 3-channel time-integrated spectrum (measured from T0-0.064 s to T0+0.084 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -0.26(-0.32,+0.40) and Ep = 537(-85,+129) keV. All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44998. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43212] GRB 260616B: AstroSat CZTI detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44997 SUBJECT: GRB 260616B: AstroSat CZTI detection DATE: 26/06/19 12:22:02 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), S.Salunke(IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260616B which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44953), EP-WXT (D. Y. Li et. al., GCN Circ. 44956), CALET (Y. Asaoka et. al., GCN Circ. 44966), Konus-Wind (A. Ridnaia et. al., GCN Circ. 44968). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 07:05:27.69. The measured peak count rate associated with the burst is 543 (+46, -48) counts/s above the background in the combined data of all quadrants, with a total of 2787 (+162, -177) counts. The local mean background count rate was 277 (+2, -3) counts/s. We measure a T90 of 13 (+2, -1) s from the cumulative CZT light curve. The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 07:05:27.10. The measured peak count rate associated with the burst is 1249 (+80, -86) counts/s above the background in the combined data of all quadrants, with a total of 5848 (+333, -346) counts. The local mean background count rate was 1225 (+5, -6) counts/s. We measure a T90 of 13 (+3, -1) s from the cumulative Veto light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/ET20260616T070516/ET20260616T0… CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/44997. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43211] GRB 260616A: AstroSat CZTI detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44996 SUBJECT: GRB 260616A: AstroSat CZTI detection DATE: 26/06/19 11:50:15 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S.Salunke(IUCAA), Utkarsh Pathak(IITB), A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 260616A which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44948), Fermi/LAT (S. Lopez et al., GCN Circ. 44960), GECAM-B (Hao-Xuan Guo et al., GCN Circ. 44964), Konus-Wind (A. Ridnaia et al., GCN Circ. 44967), Insight HXMT (Chen-Wei Wang et al., GCN Circ. 44980), NuSTAR(G. Waratkar et al., 44987). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 03:22:46.024. The measured peak count rate associated with the burst is 241 (+20, -9) counts/s above the background in the combined data of three quadrants (out of four), with a total of 16061 (+515, -588) counts. The local mean background count rate was 203 (+1, -2) counts/s. We measure a T90 of 113 (+5, -5) s from the cumulative CZT light curve. The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 03:22:44.598. The measured peak count rate associated with the burst is 724 (+35, -35) counts/s above the background in the combined data of all quadrants, with a total of 45925.00 (+1118, -1178) counts. The local mean background count rate was 1290 (+2, -3) counts/s. We measure a T90 of 112 (+3, -4) s from the cumulative Veto light curve. In the preliminary analysis, we find 2989 Compton events associated with this event. CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260616T032154/ET20260616T032154_details.html CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/44996. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43210] GRB 260616A: SVOM/GRM observation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44995 SUBJECT: GRB 260616A: SVOM/GRM observation DATE: 26/06/19 11:49:27 GMT FROM: guohx(a)ihep.ac.cn SVOM/GRM team: Hao-Xuan Guo, Chen-Wei Wang, Zheng-Hang Yu, Chao Zheng, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260616A (SVOM burst-id sb26061602) at 2026-06-16T03:21:30.000 UTC (T0), which is also detected by Fermi/GBM (Fermi/GBM team, GCN #44948, Matt Godwin et al., GCN #44971), Fermi/LAT (S. Lopez et al., GCN #44960), GECAM-B (Hao-Xuan Guo et al., GCN #44964), Konus-Wind (A. Ridnaia et al., GCN #44967), Insight-HXMT (Chen-Wei Wang et al., GCN #44980) and NuSTAR (G. Waratkar et al., GCN #44987). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 143 +5/-4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260616A.png In addition, the position of this burst, as determined by Fermi/LAT (RA = 93.53, Dec = -32.07, GCN #44960), is located at about 97 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-62 to T0+130 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.38 +0.05/-0.04 and the cutoff energy, parameterized as Epeak, is 573 +61/-52 keV. The event fluence (10-1000 keV) in this time interval is (2.14 +/-0.03)E-04 erg/cm^2. The 1s peak spectrum, measured from T0+75 to T0+76 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.45 +0.11/-0.07 and the cutoff energy, parameterized as Epeak, is (2.00 +1.47/-0.85)E+03 keV. The flux (10-1000 keV) in this time interval is (4.48 +0.15/-0.14)E-06 erg/cm^2/s. The localization of GRB 260616A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616A_amati.png The localization of GRB 260616A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616A_yonetoku.png 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 point of contact for this burst is: Hao-Xuan Guo (IHEP)(guohx(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44995. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43209] EP260618a: OHP/T193 optical observations
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44994 SUBJECT: EP260618a: OHP/T193 optical observations DATE: 26/06/19 11:05:46 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> P. Amram (LAM/Pytheas/AMU), C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU) report on behalf of a larger collaboration: We observed the field of EP260618a (Yang et al., GCN44978; see also Fermi GBM Team , GCN44973 and Jiang et al., GCN44991) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 2x10 minutes of exposure in the r-band starting at 2026-06-18T21:12:40 UT (12.63 hr after the Yang et al. trigger). In the stacked images, the optical counterpart detected by Becerra et al. (GCN44988) and Malesani et al. (GCN44990) is visible with preliminary magnitude of: r = 21.86 +/- 0.09 mag in good agreement with their measurements. The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard. We acknowledge the excellent support of J. Schmitt and J.C. Brunel in the recent MISTRAL upgrade. View this GCN Circular online at https://gcn.nasa.gov/circulars/44994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43208] GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44993 SUBJECT: GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection DATE: 26/06/19 10:18:21 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Divyanshu Janghel, Debalina kar, Pankaj Pawar, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260610B/AT 2026owq discovered by Fermi (The Fermi GBM team, GCN 44901; Godwin and Meegan; GCN 44931; Yu et al., GCN 44944)) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-06-15 at 16:53:40 UT, i.e., ~ 4.71 days after the Fermi trigger (GCN 44901). We have taken multiple frames with an exposure time of 300 s in the R and I filter. We stacked the images after the alignment. We detect a optical afterglow in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Mid_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================= 2026-06-15 17:24:09.406 ~4.73 R 300s*12 20.88 +/-0.05 The optical detection of the burst is consistent with O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek & Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959; Moskvitin et al., GCN 44963; Pankov et al., GCN 44977; Gassert et al., GCN 44981. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the Gaia DR3 Synphot catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/44993. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43207] GRB 260619A: Kilonova-Catcher optical upper limit
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44992 SUBJECT: GRB 260619A: Kilonova-Catcher optical upper limit DATE: 26/06/19 09:54:36 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> R. Hellot (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 260619A detected by SVOM/ECLAIRs (Goto et al., GCN 44985) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a CDK17 telescope located at AITP San Pedro Chile Observatory and operated by R. Hellot. Our observations started at TGRB+4.0 hours and were taken with the sdssr filter. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical uncatalogued source inside the SVOM/ECLAIRs error box. We report our follow-up results in the table below: | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | | ------------ | ------------ |------------ |------------ |------------ | | 4.29 | 12 x 300s | r (AB) | 20.3 (5 sigma) | AITP | All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). 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 (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44992. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43206] EP260618a: EP-FXT follow-up observation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44991 SUBJECT: EP260618a: EP-FXT follow-up observation DATE: 26/06/19 09:13:11 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S. Q. Jiang (NAO, CAS), J. Yang (ZZU), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the X-ray transient EP260618a (Yang et al., GCN 44978), which is possibly associated with GRB 260618A (Fermi GBM team, GCN 44973). The observation started at 2026-06-18T18:09:47 (UTC), about 9.58 hours after the initial WXT detection, with an exposure time of 3 ks. An uncatalogued source was detected within the WXT error circle at R.A. = 276.6799, DEC = 23.8439 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT spectrum can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 1.32 x 10^21 cm^-2 and a photon index of 2.09 +/- 0.13. The derived unabsorbed 0.5-10 keV flux is 1.28 (+0.13, -0.10) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The position of the uncatalogued X-ray source is consistent with the optical counterpart (Becerra et al., GCN 44988; Malesani et al., GCN 44990). Further EP-FXT follow-up observations will be arranged. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44991. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43205] EP260618a: LCO optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44990 SUBJECT: EP260618a: LCO optical counterpart confirmation DATE: 26/06/19 08:41:05 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), J. A. Quirola-Vasquez (Radboud), J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), J. Chacon (PUC), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260618a (Yang et al., GCN 44978), possibly the afterglow of GRB 260618A (Fermi GBM team, GCN 44973), using an LCO 1m telescope located at the Teide Observatory (Spain) equipped with the SINISTRO instrument. We obtained 6x300 s exposures in the SDSS-r filter starting on 2026-06-18 at 21:56:12 UT (13.56 hr after the trigger). The object reported by Becerra et al. (GCN 44988) is detected in the stack of our images, with a magnitude of r = 21.93 +/- 0.16 (AB), calibrated against the Pan-STARRS catalogue and not corrected for Galactic extinction. We note that our magnitude indicates little or no fading compared to the COLIBRÍ observation, which was carried out about 6.5 hr later (Becerra et al., GCN 44988). Further follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44990. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43204] GRB 260617A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44989 SUBJECT: GRB 260617A: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/19 08:20:00 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Torii (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260617A at 21:36:43.92 UTC on 17 June 2026 (trigger #1465767277; https://cgbm.calet.jp/cgbm_trigger/flight/1465767277/index.html) No real-time CGBM GCN Notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Fermi GBM (The Fermi GBM team et al., GCN #44969; Godwin et al., GCN #44972), Konus-Wind and Mars-Odyssey (IPN triangulation: Kozyrev et al., GCN #44982). The burst signal was seen by HXM1 and SGM. The burst light curve shows a short pulse from T-0.25 s to T-0.15 s. The T90 and T50 durations measured with the SGM data are 0.09 +/- 0.02 s and 0.05 +/- 0.01 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465767277/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44989. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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 18 Jun '26

18 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 18 Jun '26

18 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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[vsnet-grb-info 43193] EP260618a: EP-WXT detection of an X-ray transient
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44978 SUBJECT: EP260618a: EP-WXT detection of an X-ray transient DATE: 26/06/18 15:21:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. Yang (ZZU), S. Q. Jiang (NAO, CAS), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient, designated EP260618a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission through the ground data analysis. The transient was detected in one WXT observation starting at 2026-06-18T08:34:46 (UTC). No significant variability was detected during the 2.7 ks exposure. The position of the transient is R.A. = 276.676 deg, Dec. = 23.849 deg (J2000), with an uncertainty radius of 2.5 arcmin (90% confidence level, including both statistical and systematic uncertainties). There is no historical X-ray source in the WXT error circle. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a fixed Galactic hydrogen column density of 1.32^21 cm^-2 and a photon index of 1.4 (-0.4/+0.5). The derived average unabsorbed 0.5-4 keV flux is 6.9 (-1.7/+2.1) x 10^(-11) erg cm^-2 s^-1. The position of EP260618a falls within the error circle of GRB 260618A reported by Fermi/GBM (GCN 44973), suggesting that EP260618a may be the X-ray afterglow of GRB 260618A. Follow-up observation with the Follow-up X-ray Telescope (FXT) onboard EP has been scheduled. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44978. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43192] GRB 260610B: AbAO optical observations
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44977 SUBJECT: GRB 260610B: AbAO optical observations DATE: 26/06/18 10:47:10 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), R. Ya. Inasaridze (AbAO), A. Moskvitin (SAO RAS), V. Aivazyan (AbAO), A. Pozanenko (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260610B (The Fermi GBM team, GCN 44891; GCN 44901) with the AS-32 70-cm telescope of the Abastumani Astrophysical Observatory (AbAO). We acquired a series of 98x60 sec images in the R-band using a CCD-photometer, starting on 2026-06-12 20:18 UT (i.e. 1.856 days since trigger). The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek & Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959; Moskvitin et al., GCN 44963) is detected in the co-add image of 96x60 sec. The observational properties and preliminary photometry are provided further: Date UTstart t-T0 Exp. Filter Mag Err UL (mid,d) (n*s) (3-sigma) 2026-06-12 20:18:50 1.88931 96x60 R 20.59 0.10 22.0 The photometry is based on nearby SDSS stars (R-magnitudes obtained via Lupton 2005 transformation equations; Moskvitin et al., GCN 44918) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44977. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43191] EP260616a/GRB 260616B: EP-FXT follow-up observation
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44976 SUBJECT: EP260616a/GRB 260616B: EP-FXT follow-up observation DATE: 26/06/18 10:37:23 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li, T. Y. Liu (NAO, CAS), J. H. WU(GZHU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe team EP-FXT performed a follow-up observation of EP260616a/GRB 260616B (Li et al., GCN 44956; Preis & Greiner, GCN 44951; Malacaria et al., GCN 44953; Asaoka et al., GCN 44966) about 25.5 hours after the WXT detection, with an exposure time of 6.2 ks. An uncatalogued source was detected within the WXT error circle at R.A. = 256.0839, DEC = -32.3007 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT spectrum can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 3.4 x 10^21 cm^-2 and a photon index of 1.62 (+0.27, -0.26). The derived unabsorbed 0.5-10 keV flux is approximately 8.7 (+2.2, -1.7) x 10^-13 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No optical counterpart have been detected (Mandarakas et al., GCN 44965). Further EP-FXT follow-up observations will be arranged. 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/44976. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43190] GRB 260506B: cubesat Avion detection
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44975 SUBJECT: GRB 260506B: cubesat Avion detection DATE: 26/06/18 09:57:49 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> From Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2026-05-06 ~13:07:28 UT the long-duration GRB 260506B (Fermi GBM detection: GCN #44484, AstroSat CZTI detection: GCN #44503, Glowbug detection: GCN #44559) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1]. Total amount of photons detected by Avion is 428 (energy band >30 keV), it corresponds to a fluence of ~3.8*10^(-6) erg/cm^2 in the range 30-500 keV. LC in the energy range of 30-500 keV has a multiple peak structure including a faint peak of ~1 s duration at ~13:07:29 with a maximum flux of ~60 phot/(cm^2*s) and a main peak of ~5 s duration at ~13:07:40 with a maximum flux of ~80 phot/(cm^2*s) at ~13:07:42 UT. А total duration (T90) of the burst is ~15 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260506B_LC_Avion.png Parameters of GRB 260506B as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/44975. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43189] GRB 260616C: GECAM-B observation of a burst
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44974 SUBJECT: GRB 260616C: GECAM-B observation of a burst DATE: 26/06/18 07:27:43 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260616C, at 2026-06-16T14:47:01.950 UTC (denoted as T0), which is also detected by MAXI/GSC (Iwakiri et al., GCN #44961). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a pulse with a duration (T90) of 29.5 +3.5/-4.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260616C.png The time-averaged spectrum from T0-4 s to T0+8 s is best fitted by a power law function. The power law index is -2.32 +0.16/-0.13. The event fluence (10-1000 keV) in this time interval is (1.99 +0.30/-0.26)E-04 erg/cm^2. 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/44974. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43188] GRB 260618A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44973 SUBJECT: GRB 260618A: Fermi GBM Final Real-time Localization DATE: 26/06/18 06:56:28 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 06:45:34 UT on 18 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618A (trigger 803457939.281242 / 260618282). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 281.5, Dec = 21.1 (J2000 degrees, equivalent to J2000 18h 45m, 21d 06'), with a statistical uncertainty of 6.3 degrees. The angle from the Fermi LAT boresight is 72.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260618282/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44973. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43187] GRB 260617A: Fermi GBM Detection
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44972 SUBJECT: GRB 260617A: Fermi GBM Detection DATE: 26/06/18 05:18:48 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 21:36:43.68 UT on 17 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260617A (trigger 803425008/260617900). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 224.34, Dec = -12.61 (J2000 degrees, equivalent to J2000 15h 47m, -16d 43'), with a statistical uncertainty of 7.08 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 99 degrees. The GBM light curve consists of a short, bright burst with a duration (T90) of about 0.14 s (50-300 keV). The time-averaged spectrum from T0-0.08 to T0+0.259 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.56 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 700 +/- 40 keV. The event fluence (10-1000 keV) in this time interval is (7.4 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 21 +/- 1 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/44972. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43186] GRB 260616A: Fermi GBM Observation
by GCN Circulars 18 Jun '26

18 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44971 SUBJECT: GRB 260616A: Fermi GBM Observation DATE: 26/06/18 02:49:59 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 03:21:54.33 UT on 16 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616A (trigger 803272919/260616140), which was also detected by Fermi-LAT ( et al. 2026, GCN 44960). The Fermi GBM on-ground location is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 111 degrees. The GBM light curve consists of one long burst with a duration (T90) of about 69 s (50-300 keV). The time-averaged spectrum from T0+0.3 to T0+74.1 s is best fit by a Band function with Epeak = 246 +/- 1 keV, alpha = -0.63 +/- 0.01, and beta = -2.00 +/- 0.01. The event fluence (10-1000 keV) in this time interval is (1.22 +/- 0.02)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+50 s in the 10-1000 keV band is 16.9 +/- 0.4 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/44971. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43185] GRB 260617A: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44970 SUBJECT: GRB 260617A: Fermi GBM Final Real-time Localization DATE: 26/06/17 21:51:34 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 21:36:43 UT on 17 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260617A (trigger 803425008.678884 / 260617900). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 236.9, Dec = -16.7 (J2000 degrees, equivalent to J2000 15h 47m, -16d 41'), with a statistical uncertainty of 12.7 degrees. The angle from the Fermi LAT boresight is 100.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44970. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43184] GRB 260617A: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44969 SUBJECT: GRB 260617A: Fermi GBM Final Real-time Localization DATE: 26/06/17 21:49:10 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 21:36:43 UT on 17 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260617A (trigger 803425008.678884 / 260617900). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 236.9, Dec = -16.7 (J2000 degrees, equivalent to J2000 15h 47m, -16d 41'), with a statistical uncertainty of 12.7 degrees. The angle from the Fermi LAT boresight is 100.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260617900/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44969. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43183] Konus-Wind detection of GRB 260616B/EP260616a
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44968 SUBJECT: Konus-Wind detection of GRB 260616B/EP260616a DATE: 26/06/17 15:37:56 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260616B (BALROG localization: Preis & Greiner, GCN 44951; Fermi-GBM detection: Malacaria et al., GCN 44953; EP-WXT detection: Li et al., GCN 44956; CALET-GBM detection: Asaoka et al., GCN 44966) triggered Konus-Wind at T0=25522.793 s UT (07:05:22.793). The burst light curve shows two multi-peaked emission pulses. The total duration of the burst is ~13 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260616_T25522/ As observed by Konus-Wind, the burst had the total fluence of 2.52(-0.29,+0.30)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+9.760 s, of 8.62(-1.09,+1.12)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+16.832 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.78(-0.18,+0.23), the high energy photon index beta = -2.25(-0.28,+0.16), the peak energy Ep = 279(-49,+62) keV (chi2 = 101/97 dof). The spectrum near the maximum count rate (measured from T0+8.640 to T0+16.832 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.05(-0.10,+0.11) and Ep = 382(-41,+52) keV (chi2 = 87/85 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.0 (chi2 = 87/84 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44968. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43182] Konus-Wind detection of GRB 260616A
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44967 SUBJECT: Konus-Wind detection of GRB 260616A DATE: 26/06/17 15:37:03 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260616A (Fermi-GBM detection: Fermi GBM team, GCN 44948; BALROG localization: Preis & Greiner, GCN 44949; Fermi-LAT detection: Lopez et al., GCN 44960; GECAM-B detection: Guo et al., GCN 44964) triggered Konus-Wind at T0=12085.625 s UT (03:21:25.625). The burst light curve shows a bright, multipeaked pulse, which starts at ~T0-63 s and has a total duration of ~292 s. A weaker possible precursor is clearly visible in the KW waiting mode data around ~T0-422 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260616_T12085/ As observed by Konus-Wind, the burst had the total fluence of 2.77(-0.09,+0.09)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+82.880 s, of 7.35(-1.24,+1.23)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+105.984 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.76(-0.03,+0.04), the high energy photon index beta = -2.28(-0.06,+0.05), the peak energy Ep = 295(-10,+11) keV (chi2 = 118/97 dof). The spectrum near the maximum count rate (measured from T0+81.408 to T0+89.600 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.97(-0.08,+0.09), the high energy photon index beta = -2.23(-0.25,+0.15), the peak energy Ep = 379(-49,+57) keV (chi2 = 87/87 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44967. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43181] GRB 260616B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44966 SUBJECT: GRB 260616B: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/17 15:25:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260616B at 07:05:24.65 UTC on 16 June 2026 (trigger #1465628601; https://cgbm.calet.jp/cgbm_trigger/flight/1465628601/index.html) A CGBM Notice was distributed in near real time. This event was also reported by Fermi GBM (Preis et al., GCN #44951; Malacaria et al., GCN #44953). The burst signal was seen by HXM2 and SGM. The burst light curve shows a double-peaked structure starting at T-7.7 s, peaking at T+2.6 s, and ending at T+4.1 s. The T90 and T50 durations measured with the SGM data are 11.2 +/- 0.3 s and 8.1 +/- 0.2 s in the 40-1000 keV band, respectively. Einstein Probe/WXT detected an X-ray transient, EP 260616a (Li et al., GCN #44956), about 9 s before the CGBM trigger. The position of EP 260616a was marginally above the Earth horizon as seen from CALET/ISS at the trigger time, at an incident angle of 110 degrees. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465628601/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44966. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43180] EP260616a/GRB260616B: COLIBRÍ optical upper limit
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44965 SUBJECT: EP260616a/GRB260616B: COLIBRÍ optical upper limit DATE: 26/06/17 14:44:26 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), 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), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP 260616a (Li et al., GCN Circ. 44956), which is consistent in time and location with GRB 260616B (Malacaria et al., GCN Circ. 44953), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-17 05:56:39 to 07:16:28 UTC (from 22.86 to 24.20 hours after the trigger) and obtained 48 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed 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. In the stacked image, we do not detect any new source at the WXT source position (Li et al., GCN Circ. 44956) down to the following 5-sigma limit: r > 22.76 mag z > 22.20 mag 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/44965. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43179] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43178] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43177] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43176] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43175] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43174] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43173] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43172] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43171] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43170] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43169] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43168] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43167] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43166] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43165] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43164] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43163] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43162] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43161] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43160] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43159] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43158] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43157] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43156] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43155] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43154] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43153] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43152] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0