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[vsnet-grb-info 43562] The EP-WXT trigger 01709278015 is likely a flaring star
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45343 SUBJECT: The EP-WXT trigger 01709278015 is likely a flaring star DATE: 26/08/10 11:45:07 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> C.L.Guo (NAO, CAS), C.Wang (IHEP, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709278015, detected at the time of 2026-08-10 08:31:49, is likely a stellar flare associated with eclipsing binary GR* 232. The estimated flux of the flare is around 1.4e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3.1e31 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/45343. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43561] GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45342 SUBJECT: GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation DATE: 26/08/10 11:01:44 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Stéphane Basa (UAR Pytheas), Noémie Globus (UNAM), 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), 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) and Frédéric Piron (LUPM) report: We imaged the field of the SVOM GRB 260809A (Brunet et al., GCN 45331) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-1 06:18:16 to 09:10:59 UTC (from 15.3 to 18.2 hours after the trigger) and obtained 80x60 seconds of exposure in the z band. The data were reduced, coadded and analyzed with the ASU and CPPM COLIBRÍ pipelines. The photometry was calibrated using nearby stars from the PanSTARRS DR1r catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we detect the optical counterpart (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339, Izzo et al., GCN 45340) at a preliminary magnitude of: z = 23.11 +/- 0.16 Further observations 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/45342. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43560] GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45341 SUBJECT: GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation DATE: 26/08/10 09:37:48 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Stéphane Basa (UAR Pytheas), Noémie Globus (UNAM), 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), 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) and Michela Maria Dinatolo (U. Milano) report: We imaged the field of the SVOM GRB 260808B (Bouchet et al., GCN 45316) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-10 07:02:08 to 08:48:29 UTC (from 40.6 to 42.4 hours after the trigger) and obtained 48x60 seconds of exposure in the z band. The data were reduced, coadded and analyzed with the ASU and CPPM COLIBRÍ pipelines. The photometry was calibrated using nearby stars from the PanSTARRS DR1r catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we detect the optical counterpart (Turpin et al., GCN 45318; Li et al., GCN 45320; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek et al., GCN 45330) at a preliminary magnitude of: z = 22.21 +/- 0.08 Further observations 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/45341. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43559] GRB 260809A: NOT optical observations
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45340 SUBJECT: GRB 260809A: NOT optical observations DATE: 26/08/10 08:11:19 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> L. Izzo (INAF/OACN and DARK/NBI), A. Saccardi (CEA/Irfu), G. Corcoran (UCD), report on behalf of a larger collaboration: We observed the field of GRB 260809A detected by SVOM/ECLAIRs (Brunet et al., GCN 45331), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 3x300 s exposures in the SDSS r-band and 5x200s in the SDSS z-band. In the stacked images, we detect the optical afterglow (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339). We measure the following magnitudes calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r = 23.78+/-0.18, midtime: 2026-08-10 at 04:29:51 UT (13.54 hr post trigger) z = 22.25+/-0.13, midtime: 2026-08-10 at 04:47:47 UT (13.84 hr post trigger). View this GCN Circular online at https://gcn.nasa.gov/circulars/45340. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43558] GRB260809A: MAO/AZT-22 optical observations
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45339 SUBJECT: GRB260809A: MAO/AZT-22 optical observations DATE: 26/08/10 04:16:25 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> Y. Rajabov, O. Burkhonov, B.Abidkhanov, S. Ehgamberdiev, Y. Tillayev (UBAI), A. Shaymanov, T. Boyqobilov (Maidanak Observatory/UBAI) report on behalf of UBAI team. We observed the field of GRB 260809A detected by SVOM (Brunet et al., GCN 45331) with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2026-08-09 at 22:25:45 UT, i.e, ~7.47 hours after the SVOM/ECLAIRs trigger. In total we obtained 4x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). We detect the afterglow in our stacked frame at the position reported by Li et al. (GCN 45336). Our preliminary measurements consist with detections reported by Li et al. GCN 45336 and Adami et. al. GCN 45338. Preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err. UL SNR Site/Telescope (nxs) (mid, hours) 2026-08-09 22:25:45 4x300 7.47 R 22.97 0.1 23.24 6 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDWeb (Karpov 2025). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. Our measurements in Vega magnitude system and the data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) View this GCN Circular online at https://gcn.nasa.gov/circulars/45339. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43557] GRB260809A: OHP/T193 optical observations
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45338 SUBJECT: GRB260809A: OHP/T193 optical observations DATE: 26/08/10 03:11:58 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU),S. Basa (LAM/OHP/Pytheas/AMU), A. Saccardi (CEA/Irfu), B. Schneider (LAM), F. Schussler (CEA Paris-Saclay) report on behalf of a larger collaboration: We observed the field of GRB 260809A (Brunet et al., GCN45331) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 5x600 sec of exposure in the i-band under a ~2arcsec seeing, starting at 20260809_233302UT (~8.6 hr after the Brunet et al. trigger) and ending at 20260810_010555UT (~10.1 hr after the Brunet et al. trigger). We obtained 3x600 + 4x1000 sec of exposure in the r-band under a ~2arcsec seeing, starting at 20260810_001106UT (~9.2 hr after the Brunet et al. trigger) and ending at 20260810_021627UT (~11.3 hr after the Brunet et al. trigger). We obtained 900 sec of exposure in the Y-band under a ~2arcsec seeing at 20260809_234858UT (~8.9 hr after the Brunet et al. trigger), 1200 sec at 20260810_023727UT (~11.7 hr after the Brunet et al. trigger), and 1200 sec at 20260810_025838UT (~12 hr after the Brunet et al. trigger). In the preliminary stacked images, we detect in r and i bands the afterglow at the position of Li et al. (GCN 45336) with preliminary magnitudes of: r = 23.36 +/- 0.10 mag i = 22.03 +/- 0.06 mag We do not detect the source in our Y-band image. This image has a preliminary estimated limiting magnitude of Y=21.2 (3sigma). 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/45338. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43556] IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45337 SUBJECT: IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/08/09 23:42:20 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-260805A (https://gcn.nasa.gov/circulars/45294)in a time range of 1000 seconds centered on the alert event time (2026-08-05 13:53:19.709 UTC to 2026-08-05 14:09:59.709 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-260805A. 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-260805A 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 7e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-08-04 14:01:39.709 UTC to 2026-08-06 14:01:39.709 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-260805A 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/45337. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43555] GRB 260809A: SVOM/VT optical counterpart
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45336 SUBJECT: GRB 260809A: SVOM/VT optical counterpart DATE: 26/08/09 22:39:24 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, C. Wu, L. P. Xin, Y. L. Qiu, 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. T. Palmerio (CEA/Irfu), F. Piron (LUPM) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic slew for GRB 260809A, which was triggered by SVOM/ECLAIRs (sb26080907, Brunet et al., GCN 45331) and also detected by SVOM/MXT (Brunet et al., GCN 45331). The observation started at 2026-08-09T15:01:31 UTC, i.e., 238 seconds post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. An uncatalogued optical counterpart was detected within the error circles of MXT (Brunet et al., GCN 45331)and ECLAIRs (Brunet et al., GCN 45331), compared with the Legacy Survey. The position is at R.A., Dec. = 356.962498, 21.037855 degrees, equivalent to: R.A. (J2000) = 23:47:50.99 Dec. (J2000) = +21:02:16.28 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Exposure Time | Band | Brightness 263 s | 50 s | VT_B | 21.0+/-0.2 263 s | 50 s | VT_R | 18.8+/-0.1 3.02 h | 25*100 s | VT_B | 23.2+/-0.2 3.02 h | 27*100 s | VT_R | 21.5+/-0.1 The source showed a slow brightening trend in both channels during our early observations taken within 600 seconds post trigger. It then faded with a temporal decay slope of -1.2 since 1.02 hr. Given the fading of the source in our observations, we propose that it is the optical counterpart of the burst. 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/45336. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43554] EP260809a: J-band upper limit with WINTER
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45335 SUBJECT: EP260809a: J-band upper limit with WINTER DATE: 26/08/09 22:10:21 GMT FROM: tanishk.mohan(a)iitb.ac.in Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of EP260809a (Sun et al., GCN 45321 and GCN 45332) 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 2026-08-09T05:29:44.454 UTC in the J band (4.85 hr after the EP-WXT trigger), consisting of 15*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 do not detect the optical counterpart (Adami et al., GCN 45324; Jiang et al., GCN 45325; Basa et al., GCN 45326) in our stacked image. We obtain the following 5-sigma upper limit: J = 19.37 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/45335. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43553] GRB 260808B: J-band upper limit with WINTER
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45334 SUBJECT: GRB 260808B: J-band upper limit with WINTER DATE: 26/08/09 22:05:52 GMT FROM: tanishk.mohan(a)iitb.ac.in Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 260808B (Bouchet et al., GCN 45316) 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 2026-08-09T04:57:29.690 UTC in the J band (14.61 hr after the SVOM/ECLAIRs trigger), consisting of 15*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 do not detect the optical counterpart (Turpin et al., GCN 45318; Li et al., GCN 45320; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek et al., GCN 45330; and also Wang et al., GCN 45322) in our stacked image. We obtain the following 5-sigma upper limit: J = 18.82 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/45334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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