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[vsnet-grb-info 43651] GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
by GCN Circulars 23 Aug '26

23 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45430 SUBJECT: GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate DATE: 26/08/23 10:27:10 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, Y. N. Ma, Z. H. Yao, J. R. Xu, J. Wang, X. H. Han, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio, D. Turpin (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic slew for GRB 260822A, which was triggered by SVOM/ECLAIRs (sb26082201, Schanne et al., GCN 45422). The observation started at 2026-08-22T17:37:09 UTC, about 47 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate reported by SVOM/COLIBRÍ (FM-GFT) (Globus et al., GCN 45429) was detected in both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Exposure Time | Band | Brightness 1.17 h | 53*50 s | VT_B | 23.00 +/ -0.22 mag 1.17 h | 53*50 s | VT_R | 22.07 +/ -0.16 mag Further VT ToO observation is scheduled. 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/45430. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43650] GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
by GCN Circulars 23 Aug '26

23 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45429 SUBJECT: GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate DATE: 26/08/23 09:16:01 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Noémie Globus (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), 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 Damien Turpin (CEA/Irfu) report: We imaged the field of the SVOM GRB 260822A (Schanne et al., GCN Circ. 45422) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-23 04:56 to 08:40 UTC (from 12.1 to 15.8 hours after the trigger) and obtained 82 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded and analysed with the COLIBRÍ and ASU pipelines. The photometry was calibrated using nearby stars from the PanSTARRS DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we tentatively detected a faint, uncatalogued source in both bands, consistent with the SVOM/ECLAIRs error circle at: RA (J2000) = 00:09:45.57 = 2.43988 deg Dec (J2000) = +01:23:23.2 = 1.38978 deg, with an estimated astrometric uncertainty of 0.5 arcsec. The preliminary magnitude derived for that source was: r = 22.88 ± 09 z = 22.08 ± 0.14 We encourage additional observations to confirm the nature of the source. 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/45429. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43649] EP260822a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 23 Aug '26

23 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45428 SUBJECT: EP260822a: Einstein Probe detection of a fast X-ray transient DATE: 26/08/23 08:30:22 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Feng, B. Zhang (USTC), Y. Q. Zhao(USTC,PRIC), H. Sun (NAO,CAS) on behalf of the Einstein Probe (EP) team: We report the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP), designated EP260822a. EP-WXT first detected the current outburst at 2026-08-22T15:16:02 (UTC), with a flux of about 4.81×10^-11 erg/cm^2/s, located at (R.A., DEC) = (14.334 deg, 11.275 deg) and (Galactic I, b) = (125.259 deg, -51.570 deg), with a 90% positional uncertainty radius of 2.6 arcmin. Short-timescale variation is observed during the ~700s WXT exposure. The transient lasts for around 350 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a hydrogen column density of 0.78 (-0.59/+1.26) x10^22 cm^-2, and a photon index of 3.07 (-1.75/+4.08) (90% C.L. statistical and systematic). The derived average unabsorbed 0.5-4 keV flux is 2.23 (-1.47/+54.17) x 10^-10 erg s^-1 cm^-2. There is no X-ray history detection within the WXT error circle. We also note that we can not rule out the possibility that EP260822a might be the stellar flare of the star G 2-7, which is within the WXT error circle. Follow-up observations by EP-FXT have been scheduled. Multi-wavelength follow-up observations are encouraged to identify the nature of this likely new X-ray transient. 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/45428. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43648] GRB 260822A: LCO optical upper limits
by GCN Circulars 23 Aug '26

23 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45427 SUBJECT: GRB 260822A: LCO optical upper limits DATE: 26/08/23 06:10:02 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin, A. Saccardi, J. T. Palmerio (CEA/Irfu), Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), report on behalf of the SVOM mission team: We observed the field of GRB 260822A(SVOM burst-id sb26082201) detected by SVOM (Schanne et al., GCN 45422) with the LCO 1m telescope at Sutherland Observatory equipped with the Sinistro instrument. Our observation started at 2026-08-22T20:20:17 about 3.49 hours after the SVOM/ECLAIRs trigger time. We obtained 3x200 s exposures in the SDSS r and PanSTARRS-z filters. In our stacked images, we did not detect any optical transient candidate consistent with GOTO (O'Neill et al., GCN 45423) and GROWTH-India (Saikia et al. GCN 45424) observations. We measure the following upper limit magnitude calibrated against the PanSTARRS DR1 catalog, and not corrected for Galactic extinction: r > 20.2 (AB) (5 sigma, Tmid - T0 = 3.6 hr); z > 18.8 (AB) (5 sigma, Tmid - T0 = 3.6 hr). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/45427. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43647] The EP-WXT trigger 01709287395 is likely a flaring star
by GCN Circulars 23 Aug '26

23 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45426 SUBJECT: The EP-WXT trigger 01709287395 is likely a flaring star DATE: 26/08/23 01:46:42 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.Q. Zhao(USTC,PRIC), B. Zhang, J. P. Feng (USTC), H. Sun (NAO,CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709287395 at the time of 2026-08-22T20:31:42, is likely a stellar flare associated with HD197192. The source is located at ~ 40pc and has a history X-ray detection. The estimated flux of the flare is around 3.65e-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 7.08e30 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/45426. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43646] GRB260822B: Fermi GBM Final Localization
by GCN Circulars 22 Aug '26

22 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45425 SUBJECT: GRB260822B: Fermi GBM Final Localization DATE: 26/08/22 22:51:06 GMT FROM: oindabimukherjee(a)gmail.com The Fermi GBM team reports the detection of a likely SHORT GRB "At 20:21:03.83 UT on 22 August 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB260822B (trigger 809122868/260822848). This trigger was initially classified as Below horizon by the flight software, but is in fact a GRB. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 173.93, Dec = 18.48 (J2000 degrees, equivalent to J2000 11h 35m, +18d 28'), with a statistical uncertainty of 6.94 degrees. The angle from the Fermi LAT boresight is 102 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260822848/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260822848/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260822848/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/45425. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43645] GRB 260822A: GROWTH-India Telescope Upper Limits
by GCN Circulars 22 Aug '26

22 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45424 SUBJECT: GRB 260822A: GROWTH-India Telescope Upper Limits DATE: 26/08/22 20:25:52 GMT FROM: Aditya Pawan Saikia at IIT Bombay <adityaps(a)iitb.ac.in> A. P. Saikia, V. Vijaykumar, V. Swain, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of SVOM GRB 260822A (Schanne et al., GCN 45422), with the 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-08-22 19:03:46 UT, i.e., 2.2 hours after the GRB trigger. We obtained multiple exposures in r' and g'. We did not detect the source in our stacked image within the SVOM localization region (Schanne et al., GCN 45422). The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (hr) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------- | ------------ | ------------------- | ---------------- | | 61274.800179 | r' | 2.36 | 3 x 300 | 21.6 | | 61274.812419 | g' | 2.65 | 3 x 300 | 21.7 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The measurement is consistent with the reported optical measurements by O'Neill et al. (GCN 45423). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/45424. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43644] GRB 260822A: GOTO optical upper limit
by GCN Circulars 22 Aug '26

22 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45423 SUBJECT: GRB 260822A: GOTO optical upper limit DATE: 26/08/22 19:03:18 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, S. Moran, G. Ramsay, R. Starling, B. Gompertz, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, M. Pursiainen, on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM/ECLAIRS alert for GRB 260822A (Schanne et al.; GCN #45422). Observations covering the localisation area were taken at 2026-08-22 17:21:22 UT, (+0.51h post trigger). Images consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks (Lyman et al. 2026). No new transients that could be credibly associated with GRB 260822A were detected down to an average 5-sigma depth of L > 20.7 AB mag. 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/45423. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43643] GRB 260822A: SVOM detection of a short burst
by GCN Circulars 22 Aug '26

22 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45422 SUBJECT: GRB 260822A: SVOM detection of a short burst DATE: 26/08/22 17:21:32 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S. Schanne, D. Turpin, D. Götz (CEA/Irfu) report on behalf of the SVOM mission team: At 2026-08-22T16:50:36 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260822A (SVOM burst-id sb26082201). 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 Count-Rate Trigger (CRT), which produced a sequence of 5 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.62 in the [8-120] keV energy band over a time window of 0.16 seconds starting at 2026-08-22T16:50:36.63 (Tb). The localization of the best alert is R.A., Dec. 2.4240, 1.3876 degrees: R.A. (J2000) = 0h09m41.75s Dec. (J2000) = 1d23m15.50s with a 90% confidence level (C.L.) radius of 9.15 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single narrow peak with a duration of about 100 ms. This burst also triggered SVOM/GRM at 2026-08-22T16:50:36 on a timescale of 0.10 seconds with an SNR of 6.20. The SVOM/GRM light curve showed a single narrow peak with a duration of about 100 ms. SVOM slewed to the burst. At the time of the trigger, MXT was in Earth occultation. Observations performed by SVOM/MXT and SVOM/VT will be reported 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 Damien Turpin (damien.turpin(a)cea.fr) Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45422. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43642] Fermi-LAT Gamma-ray Observations of IceCube-260821A
by GCN Circulars 22 Aug '26

22 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45421 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260821A DATE: 26/08/22 15:55:23 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa(a)weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and C. Bartolini (INFN Bari) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC260821A neutrino event (GCN 45412) 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 2026-08-21 at 03:34:49.04 UTC (T0) with J2000 position RA = 116.67 (+0.49, -0.48) deg, Decl. = 10.05 (+0.44, -0.45) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC260821A localization error (FL16Y, The Fermi-LAT 16 Year Source List, The Fermi-LAT collaboration 2026, arXiv:2602.22148). 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 IC260821A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260821A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.9e-10 ph cm^-2 s^-1 for ~18-years (2008-08-04 / T0), <1.6e-08 (<1.0e-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 analysis, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). 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/45421. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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