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[vsnet-grb-info 43077] The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44922 SUBJECT: The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare DATE: 26/06/12 09:14:55 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S.J. Yin (GXU), Z. Kang (CHO), C. Wu (NAOC), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of EP-WXT trigger 01709269176 (Zhou et al., GCN 44913) with LATIOS on SVOM/C-GFT. Observations started at 2026-06-11T13:13:04.862 UTC, ~47.5 min after the trigger. Our observations in g,r and i bands confirmed that the reported associated star (GAIA DR3 1249275629854893952,GCN 44913 ) exhibits stellar flares. A flare is detected at ~5000 s post trigger, with an amplitude of ~1.3 mag in g-band and ~0.4 mag in i-band. The flare epoch is consistent with an X-ray flare detected by EP-FXT (EP team, private communication). The photometry was calibrated against nearby Pan-STARRS1 DR1 stars. We thank the observation assistants Chulei Guo and Yinhuai Hao at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcmin x 21 arcmin FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/44922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43076] GRB 260610B / AT2026owq: SVOM/VT optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44921 SUBJECT: GRB 260610B / AT2026owq: SVOM/VT optical observations DATE: 26/06/12 08:27:15 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) and J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed a ToO observation of GOTO26fua/AT2026owq (O'Neil 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), a possible counterpart of GRB 260610B (Fermi GBM Team, GCN 44901). The observation started at 2026-06-11T13:05:40 UTC, i.e., 13.32 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The OT was clearly 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 14.50 h VT_B 30*70 s 20.10 +/-0.06 mag 16.12 h VT_B 29*70 s 20.16 +/-0.06 mag 14.52 h VT_R 28*70 s 19.38 +/-0.06 mag 16.15 h VT_R 26*70 s 19.49 +/-0.06 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/44921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43075] GRB 260610B / AT2026owq: OASDG optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44920 SUBJECT: GRB 260610B / AT2026owq: OASDG optical observations DATE: 26/06/12 07:54:38 GMT FROM: luca.izzo(a)inaf.it L. Izzo (INAF-OACn, DARK/NBI, OASDG) reports: We observed the counterpart of GRB 260610B (Fermi GBM team, GCN #44901) using the 0.5-m T1 telescope of the Osservatorio Astronomico S. Di Giacomo (OASDG), located in Agerola, Italy. Our observations started on 2026 June 11 at 21:44 UT, 0.917 days after the GRB trigger. We acquired a series of 8 × 300 s images in the Rc and Ic filters. The optical counterpart, also reported as AT2026owq (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; Perley et al., GCN #44919), is clearly detected in both stacked images. We measure the following preliminary magnitudes (AB), which have been calibrated against nearby stars from the Pan-STARRS catalog and appropriately transformed to Rc and Ic magnitudes. Rc = 19.14 +/- 0.16 mag Ic = 18.88 +/- 0.16 mag View this GCN Circular online at https://gcn.nasa.gov/circulars/44920. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43074] GRB 260610B: IAC-80 Optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44919 SUBJECT: GRB 260610B: IAC-80 Optical observations DATE: 26/06/12 07:06:28 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> Dominic Jackson-Horne (UOL/LJMU), Danny McDonnell (UOL/LJMU), Esme Williams (UOL/LJMU), Daffyd Thomas (UOL/LJMU), Ruby Keeling-Roberston (UOL/LMJU), Farhan Qamar Salmo (UOL/LJMU), Oliver King (UOL/LJMU), Daniel Perley (LJMU), H.-M. S. Grabham (LJMU), and Daniel Harman (LJMU) report: We observed the optical afterglow (D. O'Neill, et al., GCN 44903) of GRB 260610B (The Fermi GBM team, GCN 44901) using the 0.82m IAC80 telescope of Teide Observatory, equipped with the CAMELOT2 optical imager. Our first set of observations commenced at 21:41 UT and concluded at 22:20 UT on June 11; a second set of observations was then taken between 01:20 UT and 02:05 UT on June 12. We report the following photometry: | Date | UTstart | t-T0 (d) | Exp (n*s) | Filter | Mag | Err | |------------|----------|----------|-----------|--------|-------|------| | 2026-06-11 | 21:41:52 | 0.931 | 3*180 | SDSS-r | 20.04 | 0.06 | | 2026-06-11 | 22:03:58 | 0.928 | 3*180 | Rc | 19.85 | 0.06 | | 2026-06-11 | 22:17:05 | 0.938 | 3*180 | Ic | 19.23 | 0.05 | | 2026-06-11 | 22:25:33 | 0.943 | 3*180 | B | 20.94 | 0.13 | | 2026-06-12 | 01:20:48 | 1.065 | 3*120 | B | 21.47 | 0.26 | | 2026-06-12 | 01:27:40 | 1.070 | 3*120 | V | 20.35 | 0.09 | | 2026-06-12 | 01:34:33 | 1.075 | 3*120 | Ic | 19.40 | 0.08 | | 2026-06-12 | 01:41:26 | 1.080 | 3*120 | SDSS-r | 20.26 | 0.09 | This preliminary photometry is calibrated relative to the SDSS star J143237.88+270028.3 (using the Lupton 2005 transformation equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43073] GRB 260610B / AT2026owq: SAO RAS optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44918 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations DATE: 26/06/11 22:05:25 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. The observations carried out in BVRcIc filters starting June 11, 19:43:01 UT (since ~ 1.4 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) is clearly detected in our frames with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-11 19:43:01 1.40315 2*300 Rc 19.73 0.03 22.6 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. The observations are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/44918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43072] GRB 260611B: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44917 SUBJECT: GRB 260611B: Fermi GBM Final Real-time Localization DATE: 26/06/11 21:44:58 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 21:32:33 UT on 11 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260611B (trigger 802906358.618188 / 260611898). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 13.3, Dec = 22.6 (J2000 degrees, equivalent to J2000 00h 53m, 22d 36'), with a statistical uncertainty of 2.2 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/bn260611898/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611898/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611898/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43071] EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44916 SUBJECT: EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068 DATE: 26/06/11 15:26:01 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), J. Sanchez-Sierras (Radboud), P. G. Jonker (Radboud), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the likely host galaxy of EP260601a/GRB 260601B (Yang et al., GCN 44766; Yu et al., GCN 44767; Wang et al., GCN 44768; Waratkar et al., GCN 44771; Sugita et al., GCN 44773) that is at the position of the optical counterpart (Liu et al., GCN 44764; Guelfand et al., GCN 44765; Li et al. GCN 44769) using the ESO Very Large Telescope (VLT) equipped with the X-shooter spectrograph. The spectrum covers the wavelength range of 3000 - 24000 AA with total exposure times of 2910, 2980 and 3000 s in the UVB, VIS and NIR arms, respectively. The observation started on 2026-06-11 at 07:39:12 UT, i.e. ~10 days after the event. We detect clear emission lines in the spectrum, which we identify as the [O II] 3726, 3729 doublet (resolved), H-gamma, and [O III] 5008 at a redshift of z = 1.068. We suggest that this is the redshift of the host galaxy of EP260601a. We thank the ESO staff at Paranal for their excellent support, in particular Celia Desgrange, Claudia Paladini, Francisco Caceres, and John Pritchard. View this GCN Circular online at https://gcn.nasa.gov/circulars/44916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43070] EP260610b: GTC likely spectroscopic redshift z = 1.10
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44915 SUBJECT: EP260610b: GTC likely spectroscopic redshift z = 1.10 DATE: 26/06/11 14:52:44 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. P. C. van Hoof (Radboud), D. Mata Sanchez (IAC and ULL), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), David Garcia Alvarez (GTC), report on behalf of a larger collaboration: We observed the optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900; Zhu et al., GCN 44902; Burkhonov et al., GCN 44904; Moreno Mendez et al., GCN 44906) of the fast X-ray transient EP260610b (Wu et al., GCN 44895; Guo et al., GCN 44912) using the Gran Telescopio Canarias (GTC) located in the island of La Palma (Canary Islands, Spain), equipped with the OSIRIS+ spectrograph. A sequence of 3x1200 s observations was secured using grism R1000B, which covers the wavelength range 3600-7790 AA. The observation mid time was 2026 Jun 11.183 UT (15.58 hr after the EP/WXT trigger). In the acquisition image (taken 14.96 hr after trigger), we measure an AB magnitude r = 23.38 +- 0.11, calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction. The delivered seeing was 0.8". Weak continuum is detected across the entire wavelength range. From the lack of hydrogen absorption, we can set a firm upper limit to the redshift z < 2.1. Weak absorption features can also be identified matching Mg II and Fe II at z = 1.10. Line-stacking analysis confirms a significant absorption system at this redshift, which we suggest to be the likely redshift of EP260610b. View this GCN Circular online at https://gcn.nasa.gov/circulars/44915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43069] GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44914 SUBJECT: GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473 DATE: 26/06/11 13:44:50 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> D. O'Neill, J. Mills, M. Pursiainen, T. Killestein, D. B. Malesani, B. P. Gompertz, J. Lyman, R. Starling, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson and A. Kumar report on behalf of the GOTO collaboration. We observed GOTO26fua/AT2026owq (O'Neill et al., GCN Circ. 44903, Watson et al., GCN Circ. 44905, Zhu et al. GCN Circ 44909, Gillanders et al. GCN Circ 44910, Akl et al. GCN Circ 44911), the optical counterpart of GRB 260610B (Fermi GBM team, GCN Circ. 44891), with the Alhambra Faint Object Spectrograph (ALFOSC) mounted on the Nordic Optical Telescope (NOT) as part of the GOTO Fast Analysis and Spectroscopy of Transients program (GOTO-FAST; Godson et al., AstroNote 2023-224). We obtained spectroscopy with ALFOSC, 2x900s total with grism #4, starting at 2026-06-10 02:10:00 (+2.5h post-trigger). We identify Mg II and Ca II absorption features at a common redshift of z=0.473, which we suggest to be the redshift of GRB 260610B. We also obtained multi-colour photometry starting at 2026-06-11 02:35 (+2.8h post-trigger) | MJD | T - T0 (hours) | Filter | AB mag | |------------ |---------------- |---------- |-------- | | 61202.1079 | 2.81 | g | 18.85 | | 61202.1090 | 2.84 | r | 18.40 | | 61202.1100 | 2.87 | i | 18.14 | | 61202.1111 | 2.90 | z | 17.92 | | 61202.1264 | 3.27 | g | 19.00 | | 61202.1275 | 3.29 | r | 18.49 | | 61202.1285 | 3.31 | i | 18.25 | | 61202.1296 | 3.34 | z | 18.04 | Magnitudes are reported in the AB system, calibrated against SDSS DR16 photometry, and are not corrected for foreground Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43068] The EP-WXT trigger 01709269176 is likely a flaring star
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44913 SUBJECT: The EP-WXT trigger 01709269176 is likely a flaring star DATE: 26/06/11 12:55:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Y.-H. I. Yin (HKU), H. Y. Ren, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269176 at the time of 2026-06-11T12:25:32, is likely a stellar flare associated with Gaia DR3 1249275629854893952. The estimated flux of the flare is around 8 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.5 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/44913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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