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

[vsnet-grb-info 43569] GRB 260809A: J-band upper limit with WINTER
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45350 SUBJECT: GRB 260809A: J-band upper limit with WINTER DATE: 26/08/10 17:58:29 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 260809A (Brunet et al., GCN 45331; also see Sun et al., GCN 45344) 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 2026-08-10T05:11:10.816 UTC in the J band (14.23 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 (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339; Izzo et al., GCN 45340; Basa et al., GCN 45342) in our stacked image. We obtain the following 5-sigma upper limit: J = 18.6 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/45350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43568] EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45349 SUBJECT: EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07 DATE: 26/08/10 17:01:42 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), B. Schneider (LAM), G. Corcoran (UCD), F.-F. Song (YNAO, CAS), A. L. Thakur (INAF/IAPS), N. R. Tanvir (U. Leicester), K. E. Heintz (DTU), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed the optical counterpart (Adami et al., GCN 45324; Jiang et al., GCN 45325; Basa et al., GCN 45326) of EP260809a (Sun et al., GCN 45321; Sun et al., GCN 45332) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. From the acquisition images (3x60s) we find a magnitude of the optical transient of r = 22.44+/-0.04 at 6.95 hr post-burst. Our spectra cover the wavelength range 3000-20000 AA, and consist of 4 exposures of 1200 s each. The observation start time was 07:46 UT on 2026 Aug 9 (7.12 hr after the EP/WXT trigger). We detect afterglow continuum in each arm, with a strong absorption trough around 4950 AA. Interpreting this as Lyman-alpha absorption at z = 3.07, we also detect weak metal lines of Si II, O I, C II, Al II, Fe II, Mg II, along with a series of H_2 Lyman-Werner band lines at the same redshift. From a preliminary analysis we determine a column density of neutral hydrogen to be log10(N(HI))=22.4+/-0.3. We also detect an intervening system at z = 1.43. We acknowledge the excellent support from the observing staff in Paranal, in particular Luca Sbordone, Israel Blanchard and Jonathan Smoker. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/45349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43567] GRB 260806A: Glowbug gamma-ray detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45348 SUBJECT: GRB 260806A: Glowbug gamma-ray detection DATE: 26/08/10 16:16:28 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260806A, also detected by CALET (trigger 1470036404). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-08-06 07:27:00.088 with a duration of 51.2 s and a total significance of about 46 sigma. The light curve comprises two multi-peaked emission structures from T0 to T0+26.6s and T0+40.5s to T0+51.2s. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/45348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43566] GRB 260808A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45347 SUBJECT: GRB 260808A: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:51:56 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260808A at 02:51:52.41 UTC on 8 August 2026 (trigger #1470192693; https://cgbm.calet.jp/cgbm_trigger/flight/1470192693/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Fermi GBM (Fermi GBM Team, GCN #45313; Preis and Greiner, GCN #45315) and NuSTAR (Waratkar et al., GCN #45327). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T-10.6 s and ending at T+4.4 s. The T90 and T50 durations measured with the SGM data are 13.4 +/- 0.9 s and 7.1 +/- 0.6 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1470192693/ 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/45347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43565] GRB 260805C: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45346 SUBJECT: GRB 260805C: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:48:32 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> N. Cannady (GSFC), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), 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 260805C at 07:27:40.04 UTC on 5 August 2026 (trigger #1469950046; https://cgbm.calet.jp/cgbm_trigger/flight/1469950046/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Glowbug (Cheung et al., GCN #45292). The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse starting at T-0.6 s and ending at T+8.0 s. The T90 and T50 durations measured with the SGM data are 7.6 +/- 0.5 s and 4.4 +/- 0.5 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1469950046/ 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/45346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43564] GRB 260804A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45345 SUBJECT: GRB 260804A: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:46:23 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> T. Tamura (Kanagawa U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu (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 260804A at 03:07:25.16 UTC on 4 August 2026 (trigger #1469848033; https://cgbm.calet.jp/cgbm_trigger/flight/1469848033/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Fermi GBM (Fermi GBM team, GCN #45281; and Glowbug (Cheung et al., GCN #45288). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T-18.7 s, peaking at T+2.4 s, and ending at T+3.3 s. The T90 and T50 durations measured with the SGM data are 20.3 +/- 1.0 s and 8.5 +/- 1.1 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1469848033/ 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/45345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43563] GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45344 SUBJECT: GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation DATE: 26/08/10 12:12:39 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: EP-FXT performed a follow-up observation of GRB 260809A detected by SVOM/ECLAIRs (Brunet et al., GCN 45331). The observation started at 2026-08-09 17:30:29 (UTC), about 2.55 hr after the SVOM trigger, with a total exposure time of around 3 ks. On-ground analysis of the FXT data found a source EPF_J234751.2+210212 at R.A. = 356.9632, deg and Dec. = 21.0368 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The source position is consistent with the optical counterpart (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339; Izzo et al., GCN 45340; Basa et al. 45342). The observed flux is approximately 4.5 × 10^-12 erg s^-1 cm^-2 in the 0.5-10 keV energy band. 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/45344. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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