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

[vsnet-grb-info 43489] GRB 260802B: Fermi GBM Final Localization
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45273 SUBJECT: GRB 260802B: Fermi GBM Final Localization DATE: 26/08/02 11:25:15 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> The Fermi GBM team reports the detection of a likely SHORT GRB "At 08:59:48.38 UT on 02 August 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260802B (trigger 807353993/260802375). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 313.40, Dec = -18.52 (J2000 degrees, equivalent to J2000 20h 53m, -18d 31'), with a statistical uncertainty of 29.68 degrees. The angle from the Fermi LAT boresight is 94 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260802375/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260802375/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260802375/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/45273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43488] GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45272 SUBJECT: GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 26/08/02 11:23:07 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Asuka Kuwata (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), Noémie Globus (UNAM), Marion Guelfand (CPPM), 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), Alan M. Watson (UNAM), Wenjin Xie(NAOC), and Runchao Chen (NJU) report: We imaged the field of the SVOM GRB 260802A (Feng et al., GCN Circ. 45270) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-02 09:26:49 to 10:36:51 UTC (from 0.0188 1.2025 hours after the trigger) and obtained 61 minutes 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 DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the ECLAIRs source position (Feng et al., GCN Circ. 45270) down to the following 5-sigma limit: z > 22.6 We note that the ECLAIRs coordinates are coincident with the EP J223759.5+531421 magnetar (Rea et al. ATel 17870) and that inspection of the most precise localisation, provided by XMM (Coti Zelati et al. ATel 17909) also shows no new counterpart down to a 3-sigma limit of: z > 23.1 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/45272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43487] The EP-WXT trigger 01709277420 is likely a flaring star
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45271 SUBJECT: The EP-WXT trigger 01709277420 is likely a flaring star DATE: 26/08/02 10:59:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H. Jiang (NJU), D. Zhu , Y.H. Cheng (YNU), H.Y. Liu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709277420 at the time of 2026-08-02T10:13:15, is likely a stellar flare associated with L 85-31. The estimated flux of the flare is around 7.8×10 ^ (-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.40×10^30 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/45271. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43486] GRB 260802A: SVOM detection of a short soft burst (possible SGR)
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45270 SUBJECT: GRB 260802A: SVOM detection of a short soft burst (possible SGR) DATE: 26/08/02 10:09:19 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Xin Feng (GXU), Hatsune Goto (RIKEN, CEA), Donghua Zhao (NAOC), Weinjin Xie (NAOC), Runchao CHEN (NJU), Feliu Lacreu (IAP), Diego Götz (CEA), report on behalf of the SVOM mission team: At 2026-08-02T09:23:10 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260802A (SVOM burst-id sb26080210). 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 3 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.09 in the [5-20] keV energy band starting at 2026-08-02T09:23:10. The localization of the best alert is R.A., Dec. 339.4431, 53.2195 degrees (J2000) with a 90% confidence level (C.L.) radius of 9.72 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs showed a single peak structure lasting about 0.2 seconds. We note that given the short and soft nature of this GRB and its location at low galactic latitude, this event could also be of Magnetar (SGR) origin. SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-08-02T09:25:42 UTC, 151 seconds after T0. Using onboard processed data we found a possible uncatalogued X-ray source with a low SNR, located at R.A., Dec. 339.439, 53.234 degrees: R.A. (J2000) = 22h37m45s Dec. (J2000) = 53d14m02s with a 90% C.L. radius of 161 arcseconds. This location is 0.89 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 Wenjin Xie: xiewj(a)bao.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43485] GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45269 SUBJECT: GRB 260727A: EP-FXT further follow-up observations and candidate afterglow DATE: 26/08/02 07:33:20 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Ziming Wang (BNU), Ruizhi Li (YNAO), An Li (BNU), Yifang Liang (PMO), Wenjin Xie (NAOC), Donghua Zhao (NAOC), Clara Plasse (HKU) report on behalf of the SVOM mission team: EP-FXT performed a second epoch of follow-up observation of GRB 260727A (Li et al., GCN 45220; Harsha K. H. et al., GCN 45225; Cheung et al., GCN 45233; Svinkin et al., GCN 45242; Wang et al. GCN 45247). The follow-up observation started at 2026-07-30 00:38:00 (UTC), about 72.3 hours after the SVOM-ECLAIRs trigger, with a total exposure time of around 2.5 ks. A faint X-ray source was detected at the position of the uncatalogued X-ray source (Li et al., GCN 45236). The 0.5-10 keV spectrum can be fitted by an absorbed powerlaw model with a Galactic hydrogen column density of 0.55 x 10^22 cm^-2 and a photon index of 2.09 +1.07/-1.29. The average unabsorbed flux is 1.58 (+2.52, -0.93) x 10^(-13) erg/s/cm^2 in the 0.5-10 keV energy band (90% C.L.). The Burst Advocate (BA) on shift for this alert is Ziming Wang: 202421101144(a)mail.bnu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43484] GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
by GCN Circulars 02 Aug '26

02 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45268 SUBJECT: GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay DATE: 26/08/02 05:29:56 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, 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), and J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed further observations of GRB 260618B detected by Fermi/GBM (Fermi GBM team et al., GCN 44979; Veres et al., GCN 45010), Fermi/LAT (Gupta et al., GCN 44983), and Konus-Wind (Ridnaia et al., GCN 45038). The observation started at 2026-07-29T02:00:37 UTC, about 40.38 d post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate (Li et al., GCN 45001, GCN 45151; Shi et al., GCN 45014; Ma et al., GCN 45173) showed a steeper decay with a slope of -0.8 in both channels starting from about 21.6 d post trigger, and its color became redder. The following measurements are in AB magnitudes and are not corrected for Galactic extinction: Mid time (d) | Exposure Time (s) | Band | Brightness (mag) 40.43 | 60*70 | VT_B | 22.9 +/- 0.2 40.43 | 58*70 | VT_R | 22.2 +/- 0.2 The nature of the source remains unclear. More follow-up observations are encouraged. 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/45268. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43483] GRB 260731A: AstroSat CZTI detection of a long burst
by GCN Circulars 01 Aug '26

01 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45267 SUBJECT: GRB 260731A: AstroSat CZTI detection of a long burst DATE: 26/08/01 12:45:41 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S.Salunke(IUCAA), Harsha K. H. (IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260731A which was also detected by SVOM (Trigger Num. sb26073115) and Konus-Wind (IPN Notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-07-31 23:58:22.466 UTC. The measured peak count rate associated with the burst is 314 (+34, -33) counts/s above the background in the combined data of three quadrants (out of four), with a total of 2019 (+162, -264) counts. The local mean background count rate was 202 (+4, -3) counts/s. We measure a T90 of 11 (+3, -3) s from the cumulative CZT light curve. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-07-31 23:58:21.203 UTC. The measured peak count rate associated with the burst is 417 (+49, -5) counts/s above the background in the combined data of all quadrants, with a total of 1801 (+233, -234) counts. The local mean background count rate was 591 (+3, -4) counts/s. We measure a T90 of 8 (+4, -2) s from the cumulative Veto light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260731T235830/ET20260731T235830_details.html CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/45267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43482] Fermi-LAT Gamma-ray Observations of IceCube-260722A
by GCN Circulars 01 Aug '26

01 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45266 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260722A DATE: 26/08/01 07:03:30 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science) 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 IC260722A neutrino event (GCN 45194) 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 2026-07-22 at 06:58:22.82 UTC (T0) with J2000 position RA = 190.55 (+1.03, -1.33) deg, Decl. = 31.0 (+0.67, -0.64) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC260722A 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 IC260722A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260722A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.8e-10 ph cm^-2 s^-1 for ~18-years (2008-08-04 / T0), <4.0e-09 (<4.6e-08) 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 L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). 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/45266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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