August 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[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…

1 0

[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…

1 0

[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…

1 0

[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…

1 0

[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…

1 0

[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…

1 0

[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…

1 0

[vsnet-grb-info 43552] GRB 260808B: SVOM/ECLAIRs refined analysis
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45333 SUBJECT: GRB 260808B: SVOM/ECLAIRs refined analysis DATE: 26/08/09 19:10:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Authors: M. Brunet, L. Bouchet, S. Guillot (IRAP), Michela Dinatolo (U. Milano) report on behalf of the SVOM/ECLAIRs team Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260808B (SVOM burst-id sb26080812 – GCN 45316, trigger time T0 = 2026-08-08T14:20:58 UTC). The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve with a possible precursor at T0-84.5 s lasting around 2 s. The burst duration is T90 = 178 +12/-8 s in the 4-120 keV energy band. The time-averaged spectrum before the slew, from T0-45s to T0+43s in the 5-120 keV energy range is best fitted by a powerlaw model with alpha = -1.96 +0.14/-0.16. With this model, the 4-120 keV fluence is 6.4 +/-0.9 e-7 erg/cm^2 and the 4-120 keV photon flux is 0.32 +/-0.03 ph/cm^2/s. The possible precursor is too faint to extract any significant spectral parameters. All the quoted errors are at the 68% confidence level. 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: L. Bouchet (IRAP) (laurent.bouchet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45333. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43551] EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45332 SUBJECT: EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation DATE: 26/08/09 17:58:56 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. X. Sun(NAO, CAS), Q. J. Huang (PMO, CAS), K. J. Zhang(YNU), J. P. Chen (SYSU), Z. X. Ling(NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260809a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Sun et al., GCN 45321) and followed by several optical telescopes (Adami et al., GCN 45324; Jiang et al., GCN 45325; Basa et al., GCN 45326 ) . The refined analysis of the WXT data shows that the event started at T0=2026-08-09T00:38:21(UTC) and lasted for 34 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*tbabs*cflux*powerlaw), with the Galactic hydrogen column density fixed at 8.24 × 10^20 cm^-2. The best-fit photon index is 1.74 (-0.63/+0.88), and the additional hydrogen column density is 1.25 (-1.25/+2.23) × 10^21 cm^-2. The derived average unabsorbed 0.5–4 keV flux is 3.32 (-0.77/+0.98) × 10^-9 erg s^-1 cm^-2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2026-08-09T01:25:57(UTC), about 47.6 minutes after T0. The exposure time of this observation is 3020 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 328.5791, 17.6054 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). 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 8.24 × 10^20 cm^-2 and a photon index of 2.00 (-0.28/+0.29), and the intrinsic hydrogen column density is 0.08 (-/+0.08) × 10^22 cm^-2. The derived average unabsorbed 0.5-10 keV flux is 1.27(-0.12/+0.14)× 10^(-12) 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/45332. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43550] GRB 260809A: SVOM detection of a faint burst
by GCN Circulars 09 Aug '26

09 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45331 SUBJECT: GRB 260809A: SVOM detection of a faint burst DATE: 26/08/09 15:24:53 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP), F. Piron (LUPM), D.Gotz (CEA), A. Saccardi (CEA) report on behalf of the SVOM mission team: At 2026-08-09T14:57:33 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260809A (SVOM burst-id sb26080907). 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 2 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.20 in the [8-120] keV energy band over a time window of 20.48 seconds starting at 2026-08-09T14:57:13. The localization of the best alert is R.A., Dec. 356.820, 20.969 degrees (J2000) with a 90% confidence level (C.L.) radius of 10.88 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-08-09T15:00:23 UTC, 170 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 356.9664, 21.0347 degrees: R.A. (J2000) = 23h47m51s Dec. (J2000) =21d02m04s with a 90% C.L. radius of 94 arcseconds. This location is 9.09 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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 Frédéric Piron: piron(a)in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45331. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0