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

[vsnet-grb-info 43599] GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45379 SUBJECT: GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295 DATE: 26/08/13 20:00:32 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), S. Geier (GTC), M. A. Aloy (UV), C. C. Thoene (AbAO), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), L. Izzo (INAF/OACN and DARK/NBI), G. Lombardi (GTC), A. Martin-Carrillo (UCD), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), A. Cabrera-Lavers (GTC), A. M. Garcia Rodriguez (GTC) report: We observed the optical counterpart (Turpin et al., GCN 45318; Li et al., GCN 45320), recently reported to be brightening (Li et al., GCN 45359; Guelfand et al., GCN 45364) of GRB 260808B (Bouchet et al., GCN 45316; Brunet et al., GCN 45333) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In a 30-s acquisition image (beginning on 2026-08-13 at 02:07:19 UT, that is 4.49 days after trigger), the optical afterglow is well detected with a magnitude of 21.70 +- 0.10 (AB), calibrated against nearby Pan-STARRS objects, and not corrected for Galactic extinction. Our measurement confirms the rebrightening (Li et al., GCN 45359; Guelfand et al., GCN 45364). A total of 3 spectra of 1200 s were secured, starting on 2025-08-13 at 02:10:52 UT (mid time 4.51 days after trigger), using grism R1000B. Continuum is visible over the wavelength range 3620-7800 AA. A number of metal absorption features are detected, which we interpret as due to Fe II, Mg II and Mg I, all at a common redshift z = 1.295, which we suggest to be the redshift of GRB 260808B. This work has used the GRBspec database at http://grbspec.eu (de Ugarte Postigo et al. 2014, doi:10.1117/12.2055774). View this GCN Circular online at https://gcn.nasa.gov/circulars/45379. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43598] GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45378 SUBJECT: GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803) DATE: 26/08/13 19:45:08 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 808341387 at 19:16:22 on 13 Aug. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 240.3 deg Decl.(2000.0) = -61.7 deg The 1 sigma statistical error radius is 3.0 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260813803/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260813803/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260813803/json View this GCN Circular online at https://gcn.nasa.gov/circulars/45378. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43597] GRB 260813A: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45377 SUBJECT: GRB 260813A: Fermi GBM Final Real-time Localization DATE: 26/08/13 19:26:57 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 19:16:22 UT on 13 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260813A (trigger 808341387.08523 / 260813803). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 231.4, Dec = -57.8 (J2000 degrees, equivalent to J2000 15h 25m, -57d 47'), with a statistical uncertainty of 2.5 degrees. The angle from the Fermi LAT boresight is 46.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260813803/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260813803/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260813803/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45377. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43596] EP260812a: NOT and Liverpool Telescope upper limits:
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45376 SUBJECT: EP260812a: NOT and Liverpool Telescope upper limits: DATE: 26/08/13 15:24:20 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> G. Corcoran (UCD), R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), R. L. C. Starling (Leicester), V. Vuolteenaho (NOT / University of Oulu), K. Kisielowski (ING / University of Groningen), R. Vieliute (ING / University of St Andrews) report on behalf of a larger collaboration: We observed the field of the Einstein Probe fast X-ray transient EP260812a (Liu et al., GCN 45362) with the Nordic Optical Telescope (NOT) using the ALFOSC camera and the Liverpool Telescope (LT) using the IO:O camera. NOT observations started on 2026-08-12 at 20:52:46 UT (9.53 hr post trigger), while LT observations began on 2026-08-12 at 23:23:50 UT (12.06 hr post trigger). We do not identify any new object brighter than our reference Pan-STARRS image sensitivity limit, however our observations are deeper. We note the presence of one possible source, detected in both the NOT and LT r-band images, located at coordinates RA, Dec = 20:45:45.28, +14:09:21.3 (J2000), for which we measure a magnitude of r = 23.87 +/- 0.24 (AB) from the NOT images. However, as our observations cannot establish if this is a new source, further follow up observations are encouraged and planned. A summary of our observations is presented below. | Telescope | Mid time (hr) | Band | Exptime (s) | Limit mag (3 sigma) | | --- | -- | -- | -- | -- | | NOT | 9.66 | r| 3 x 300 | 24.11 | | NOT | 9.96 | z| 5 x 200 | 22.99 | | LT | 12.16 | r | 4 x 150 | 23.57 | | LT | 12.44 | z | 5 x 150 | 22.60 | Our photometry is in the AB system, calibrated against Pan-STARRS and not corrected for Galactic extinction. These limits are consistent with those reported by Yin et al. (GCN 45372). View this GCN Circular online at https://gcn.nasa.gov/circulars/45376. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43595] EP260812b: Liverpool Telescope observations
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45375 SUBJECT: EP260812b: Liverpool Telescope observations DATE: 26/08/13 14:50:30 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD) and R. L. C. Starling (Leicester) report on behalf of a larger collaboration: We observed the field of the Einstein Probe fast X-ray transient EP260812b (Li et al., GCN 45368) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 5x150 s exposures in each of the SDSS r’ and z’ filters starting on 2026-08-12 at 23:59:13 UT, approximately 0.39 hr after the X-ray detection. We detect the optical counterpart (Malesani et al., GCN 45367; Ma et al., GCN 45370; Gill et al., GCN 45371; Starling et al., GCN 45374) in both bands and measure the following photometry, calibrated to Pan-STARRS and not corrected for Galactic extinction: | t_mid - t0 (min) | Filter | AB magnitude | | ------------- | ------ | ------------ | | 31.8 | r’ | 20.33 +/- 0.03 | | 47.5 | z’ | 20.08 +/- 0.04 | Our photometry is consistent with that of Malesani et al. (GCN 45367) at a comparable time. View this GCN Circular online at https://gcn.nasa.gov/circulars/45375. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43594] EP260812b: GOTO detection of the optical counterpart
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45374 SUBJECT: EP260812b: GOTO detection of the optical counterpart DATE: 26/08/13 12:51:47 GMT FROM: Rhaana Starling at U of Leicester <rlcs1(a)leicester.ac.uk> R. Starling, D. O'Neill, B. P. Gompertz, G. Ramsay, S. Belkin, A. Kumar, 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, M. Pursiainen, on behalf of the 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 Einstein Probe detected X-ray transient EP260812b (ID: 01709278129, Li et al. 2026, GCN 45368). Images consisted of 4x90s exposures in the GOTO L-band (400-700 nm) and 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). We detect the optical counterpart (Malesani et al. GCN 45367; Ma et al. GCN 45370; Gill et al. GCN 45371) at 3-sigma confidence with the following magnitudes | Time (UT) | t-t0 (min) | ABmag and 1-sigma error | | ------------------- | ------------ | ----------------------- | | 2026-08-12 23:46:46 | 10.9 | 20.49 ± 0.22 | | 2026-08-13 00:55:02 | 79.2 | 20.66 ± 0.26 | Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. 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/45374. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43593] EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45373 SUBJECT: EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation DATE: 26/08/13 11:10:34 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, H. R. Ren, Tian-Yu Liu and H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260812a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Liu et al., GCN 45362) and followed by Yin et al., GCN 45372. The refined analysis of the WXT data shows that the event started at T0=2026-08-12T11:20:03(UTC) and lasted for 60 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. The best-fit photon index is 1.54 (-0.82/+0.88), and the hydrogen column density is 3.3 (-2.6/+2.9) × 10^21 cm^-2. The derived average unabsorbed 0.5–4 keV flux is 2.72 (-0.73/+1.59) × 10^-9 erg s^-1 cm^-2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2026-08-12 11:25:03(UTC), about 5 minutes after T0. The exposure time of this observation is 3898 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 311.4373, 14.1577 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 fitted Galactic equivalent hydrogen column density of 1.0 × 10^21 cm^-2 and a photon index of 2.00 (-0.08/+0.08). The derived average unabsorbed 0.5-10 keV flux is 2.61(-0.14/+0.15)× 10^(-11) erg/s/cm^2. The uncertainties are at the 1 sigma 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/45373. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43592] EP260812a: SVOM/C-GFT optical upper limit
by GCN Circulars 13 Aug '26

13 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45372 SUBJECT: EP260812a: SVOM/C-GFT optical upper limit DATE: 26/08/13 06:50:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S.J. Yin (GXU), Z. Kang (CHO), Y.X. Guan (GXU), C. Wu (NAOC), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of EP260812a detected by EP-WXT (Liu et al., GCN 45362) with LATIOS on SVOM/C-GFT. Observations started at 2026-08-12T11:28:12 UTC, ~ 7.2 minutes after the trigger. We obtained r-band follow-up imaging（Poor weather interrupted the observations, affecting image quality）. After preliminary analysis，no credible candidate was detected within the error box provided by EP-WXT (Liu et al., GCN 45362) in our images. We measure the following upper limit calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: r > 18.3 AB (3-sigma, mid-time 27.5 min after the trigger). We thank the observation assistants B.-W. Li and H.-X. Xue at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcmin x 21 arcmin FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/45372. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43591] EP260812b: COLIBRÍ optical observations
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45371 SUBJECT: EP260812b: COLIBRÍ optical observations DATE: 26/08/13 05:15:41 GMT FROM: Ramandeep Gill <rsgill.rg(a)gmail.com> Ramandeep Gill (UNAM), Massimiliano Lincetto (CPPM), Noémie Globus (UNAM), Enrique Moreno Méndez (UNAM), Dalya Akl (NYUAD), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of EP260812b (Malesani et al., GCN Circ. 45367; Li et al., GCN Circ. 45368; Ma et al., GCN Circ. 45370) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-08-13 04:08 to 04:59 UTC (from 04.55 to 05.40 hours after the trigger) and obtained 38 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We clearly detect the optical counterpart reported by Malesani et al., GCN Circ. 45367 at preliminary magnitudes of: r = 21.55 +/- 0.05, z = 21.40 +/- 0.44, consistent with the measurements reported by NOT (Malesani et al., GCN Circ. 45367), SVOM/VT (Ma et al., GCN Circ. 45370). 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/45371. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43590] EP260812b: SVOM/VT optical observation
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45370 SUBJECT: EP260812b: SVOM/VT optical observation DATE: 26/08/13 04:09:25 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, Y. L. Qiu, C. Wu, L. P. Xin, Z. H. Yao, J. R. Xu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260812b detected by EP/WXT (Li et al., GCN 45368). SVOM/VT began observing the field at 2026-08-13T00:45:07 UTC, 1.157 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Malesani et al., GCN 45367) was detected in both VT_B and VT_R bands within EP/FXT error range (Li et al., GCN 45368). The AB magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|-------------- 1.26 | 14*50 | VT_B | 20.98+-0.07 1.26 | 14*50 | VT_R | 20.62+-0.07 Preliminary photometric analysis shows a fading of approximately 0.6 mag from 1.26 h to 2.97 h, with a fading slope of ~0.6. Our photometry was not corrected for Galactic extinction. 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/45370. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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