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[vsnet-grb-info 43080] IceCube-260610A: No candidates from the Zwicky Transient Facility
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44925 SUBJECT: IceCube-260610A: No candidates from the Zwicky Transient Facility DATE: 26/06/12 17:49:32 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), Cristobal Zilleruelo Cañas (DESY), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260610A (IceCube Collaboration 2026, GCN 44899) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-06-11 06:12 UTC, approximately 10.2 hours after event time. We covered 95.9% (4.6 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/44925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43079] IceCube-260610A: EP-FXT follow-up observation
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44924 SUBJECT: IceCube-260610A: EP-FXT follow-up observation DATE: 26/06/12 12:01:23 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, Q. Y. Wu and Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT conducted a follow-up observation of IceCube-260610A (GCN 44899), a Gold-track neutrino event. The observation began at 2026-06-10T21:56:33, approximately 1.9 hours after the neutrino trigger, with a total exposure of 7.9 ks. Within the neutrino localization uncertainty region, none of the detected X-ray sources exhibited significant variability compared with their historical fluxes or upper limits. The properties of the detected sources, excluding those clearly associated with stars, are summarized below. Name | RA | Dec | Flux (erg /cm^2 /s) | Flux error (erg /cm^2 /s) | SNR EPF_J203646.2+370943 | 309.1926 | 37.1612 | 6.52e-14 | 1.71e-14 | 5.14 EPF_J203731.0+370929 | 309.3791 | 37.1577 | 5.66e-14 | 1.99e-14 | 4.72 EPF_J203711.7+370245 | 309.2994 | 37.0434 | 1.05e-13 | 2.00e-14 | 8.60 EPF_J203710.6+370109 | 309.2940 | 37.0191 | 5.46e-14 | 1.38e-14 | 6.10 EPF_J203748.1+370629 | 309.4505 | 37.1080 | 5.80e-14 | 1.54e-14 | 5.06 EPF_J203709.1+365818 | 309.2880 | 36.9716 | 6.02e-14 | 1.65e-14 | 4.40 EPF_J203803.5+371737 | 309.5105 | 37.2954 | 9.50e-14 | 2.40e-14 | 5.00 EPF_J203717.9+365622 | 309.3246 | 36.9393 | 5.75e-14 | 1.67e-14 | 4.24 EPF_J203730.0+373440 | 309.3750 | 37.5779 | 1.36e-13 | 5.01e-14 | 4.84 EPF_J203737.9+365019 | 309.4045 | 36.8384 | 7.51e-14 | 2.50e-14 | 4.75 EPF_J203835.0+364342 | 309.6481 | 36.7285 | 2.01e-13 | 4.98e-14 | 6.20 EPF_J203601.0+363247 | 309.0040 | 36.5464 | 2.38e-13 | 8.65e-14 | 3.60 We note that EPF_J203835.0+364342 is associated with a CV named ASASSN -16ix. Additional follow-up observations are planned. View this GCN Circular online at https://gcn.nasa.gov/circulars/44924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43078] GRB 260611B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44923 SUBJECT: GRB 260611B: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/12 10:12:20 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Nakahira (JAXA), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), Y. Asaoka (ICRR), 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 260611B at 21:32:32.02 UTC on 11 June 2026 (trigger #1465248636; https://cgbm.calet.jp/cgbm_trigger/flight/1465248636/index.html) A CGBM Notice was distributed in near real time. This event was also reported by Fermi GBM (Fermi GBM Team., GCN #44917). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T+0.2 s, peaking at T+14.7 s, and ending at T+28.4 s. The T90 and T50 durations measured with the SGM data are 24.7 +/- 0.9 s and 13.5 +/- 1.2 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465248636/ 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/44923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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