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

[vsnet-grb-info 43542] GRB0808B: OHP/T193 optical observations
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45323 SUBJECT: GRB0808B: OHP/T193 optical observations DATE: 26/08/09 03:41:48 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), B. Schneider (LAM), A. Saccardi (CEA/Irfu), S. Basa (LAM/OHP/Pytheas/AMU) report on behalf of a larger collaboration: We observed the field of GRB 260808B (Bouchet et al., GCN45316; see also Wang et al., GCN45322) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 7x10 + 1x5 minutes of exposure in the i-band and 6x20minutes in the Y-band under a 2.3arcsec seeing, starting at 20260808_223518UT (~8.3 hr after the Bouchet et al. trigger) and ending at 20260809_021419UT (~11.9 hr after the Bouchet et al. trigger). In the preliminary stacked images, we detect in i’ band the afterglow at the position of Turpin et al. (GCN 45318) and Li et al. (GCN 45320) at a preliminar magnitude of: i = 22.63 +/- 0.13 mag We do not detect the source in our Y-band image. This image has a preliminar estimated limiting magnitude of Y=21.8 (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/45323. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43541] GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45322 SUBJECT: GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation DATE: 26/08/09 03:21:32 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO, CAS; UCB), H. C. Ding (AHNU), R. X. Hu (WHU), Z. X. Li (IHEP, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of GRB 260808B detected by SVOM/ECLAIRs (Bouchet et al., GCN 45316). The observation started at 2026-08-08 15:55:38 (UTC), about 1.6 hr after the SVOM trigger, with a total exposure time of around 4 ks. On-ground analysis of the FXT data found a source EPF_J230056.0+082842 at R.A. = 345.2350 deg and Dec. = 8.4771 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The source position is consistent with the optical afterglow confirmed by SVOM/VT (Li et al., GCN 45320). The observed flux is approximately 1.6 × 10^-13 erg s^-1 cm^-2. 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/45322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43540] EP260809a: Einstein Probe detection of an X-ray transient
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45321 SUBJECT: EP260809a: Einstein Probe detection of an X-ray transient DATE: 26/08/09 02:46:04 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: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260809a. The transient triggered EP-WXT (ID: 01709277768) at 2026-08-09T00:38:56 (UTC). The WXT position of the source is R.A. = 328.573 deg, DEC = 17.607 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 328.5816 deg, DEC = 17.6072 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/45321. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43539] GRB 260808B: SVOM/VT optical candidate from VHF data
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45317 SUBJECT: GRB 260808B: SVOM/VT optical candidate from VHF data DATE: 26/08/08 16:03:31 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin (CEA/Irfu), C. Wu (NAOC), A. Saccardi (CEA/Irfu), L. P. Xin (NAOC), M. Dinatolo (U. Milano), report on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2026-08-08T14:20:58 UTC (T0), SVOM performed an automatic slew on the burst location (sb26080812, Bouchet et al., GCN 45316). SVOM/VT began observing the field in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the source list and 1-bit subimage downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 40: The position of this candidate is R.A., Dec. 345.23359 8.47848 degrees, corresponding to: R.A. (J2000) = 23:00:56.06 Dec. (J2000) = +08:28:42.5 with an uncertainty of 0.5 arcsec. This candidate was detected in both VT_R and VT_B in the first sequence of images and no longer detected in the following ones. No minor planet objects were found at the position of the candidate and within a 1 arcmin radius. No catalogue source was found in the Legacy DR10 catalog. The candidate's magnitudes are: | date-obs (UTC) | mid-time（sec） | exposure | VT_B mag(AB) | VT_R mag(AB) | | -------------------- | ----------- | --------- | ------------- | ------------- | | 2026-08-08T14:25:16.000 | 408 | 6x50s | 21.72 ± 0.10 | 21.02 ± 0.08 | Magnitudes were not corrected for Galactic reddening. 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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The Burst Advocate (BA) on shift for this alert is Michela Maria Dinatolo: michela.dinatolo(a)unimi.it. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43538] GRB 260808B: SVOM/VT optical afterglow confirmation
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45320 SUBJECT: GRB 260808B: SVOM/VT optical afterglow confirmation DATE: 26/08/08 18:38:06 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), M. Dinatolo (U. Milano) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic slew for GRB 260808B triggered by SVOM/ECLAIRs (sb26080812, Bouchet et al., GCN 45316) and detected by SVOM/MXT (Bouchet et al., GCN 45316). The observation started at 2026-08-08T14:24:26 UTC, i.e., 208 seconds post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate (Damien et al., GCN 45318) was detected in both channels. The position is at R.A., Dec. = 345.233538, 8.478528 degrees, equivalent to: R.A. (J2000) = 23:00:56.05 Dec. (J2000) = +8:28:42.70 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 233 s VT_B 50 s 20.9 +/- 0.2 mag 233 s VT_R 50 s 20.3 +/- 0.1 mag 1.51 h VT_B 16*50 s 22.8 +/- 0.2 mag 1.51 h VT_R 16*50 s 22.0 +/- 0.2 mag The source faded rapidly with a temporal decay slope of -1.9 in both channels during our early observations taken within 400 seconds post trigger. 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/45320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43537] GRB 260808C: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45319 SUBJECT: GRB 260808C: Fermi GBM Final Real-time Localization DATE: 26/08/08 16:34:47 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 SHORT GRB At 16:24:14 UT on 8 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260808C (trigger 807899059.114984 / 260808683). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 214.2, Dec = 34.1 (J2000 degrees, equivalent to J2000 14h 16m, 34d 06'), with a statistical uncertainty of 13.2 degrees. The angle from the Fermi LAT boresight is 36.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260808683/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260808683/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260808683/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45319. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43536] GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45318 SUBJECT: GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 ) DATE: 26/08/08 16:29:07 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin (CEA/Irfu), C. Wu (NAOC), A. Saccardi (CEA/Irfu), L. P. Xin (NAOC), M. Dinatolo (U. Milano), report on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2026-08-08T14:20:58 UTC (T0), SVOM performed an automatic slew on the burst location (sb26080812, Bouchet et al., GCN 45316). SVOM/VT began observing the field in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the source list and 1-bit subimage downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 40: The position of this candidate is R.A., Dec. 345.23359 8.47848 degrees, corresponding to: R.A. (J2000) = 23:00:56.06 Dec. (J2000) = +08:28:42.5 with an uncertainty of 0.5 arcsec. This candidate was detected in both VT_R and VT_B in the first sequence of images and no longer detected in the following ones. No minor planet objects were found at the position of the candidate and within a 1 arcmin radius. No catalogue source was found in the Legacy DR10 catalog. The candidate's magnitudes are: | date-obs (UTC) | mid-time（sec） | exposure | VT_B mag(AB) | VT_R mag(AB) | | -------------------- | ----------- | --------- | ------------- | ------------- | | 2026-08-08T14:25:16.000 | 408 | 6x50s | 21.72 ± 0.10 | 21.02 ± 0.08 | Magnitudes were not corrected for Galactic reddening. 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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The Burst Advocate (BA) on shift for this alert is Michela Maria Dinatolo: michela.dinatolo(a)unimi.it. Please contact the BA by email if you require additional information View this GCN Circular online at https://gcn.nasa.gov/circulars/45318. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43535] GRB 260808B: SVOM/VT optical candidate from VHF data
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45317 SUBJECT: GRB 260808B: SVOM/VT optical candidate from VHF data DATE: 26/08/08 16:03:31 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin (CEA/Irfu), C. Wu (NAOC), A. Saccardi (CEA/Irfu), L. P. Xin (NAOC), M. Dinatolo (U. Milano), report on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2026-08-08T14:20:58 UTC (T0), SVOM performed an automatic slew on the burst location (sb26080812, Bouchet et al., GCN 45316). SVOM/VT began observing the field in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the source list and 1-bit subimage downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 40: The position of this candidate is R.A., Dec. 349.76751, 13.62404 degrees, corresponding to: R.A. (J2000) = 23:19:04.2 Dec. (J2000) = +13:37:26.5 with an uncertainty of 0.5 arcsec. This candidate was detected in both VT_R and VT_B in the first sequence of images and no longer detected in the following ones. No minor planet objects were found at the position of the candidate and within a 1 arcmin radius. No catalogue source was found in the Legacy DR10 catalog. The candidate's magnitudes are: | date-obs (UTC) | mid-time（sec） | exposure | VT_B mag(AB) | VT_R mag(AB) | | -------------------- | ----------- | --------- | ------------- | ------------- | | 2026-08-08T14:25:16.000 | 408 | 6x50s | 21.72 ± 0.10 | 21.02 ± 0.08 | Magnitudes were not corrected for Galactic reddening. 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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The Burst Advocate (BA) on shift for this alert is Michela Maria Dinatolo: michela.dinatolo(a)unimi.it. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43534] GRB 260808B: SVOM detection of a faint burst
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45316 SUBJECT: GRB 260808B: SVOM detection of a faint burst DATE: 26/08/08 15:12:17 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Laurent Bouchet (IRAP), Sebastien Guillot (IRAP), Michela Dinatolo (U. Milano), Diego Götz (CEA) report on behalf of the SVOM mission team: At 2026-08-08T14:20:58 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260808# (SVOM burst-id sb26080812). 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 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.52 in the [5-20] keV energy band over a time window of 40.96 seconds starting at 2026-08-08T14:20:18. The localization of the best alert is R.A., Dec. 345.2202, 8.4310 degrees (J2000) with a 90% confidence level (C.L.) radius of 10.44 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-08-08T14:23:30 UTC, 152 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 345.239, 8.467 degrees: R.A. (J2000) = 23h00m57.38s Dec. (J2000) = 8d28m00.34s with a 90% C.L. radius of 48 arcseconds. This location is 2.42 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 Michela Maria Dinatolo: michela.dinatolo(a)unimi.it. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45316. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43533] GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
by GCN Circulars 08 Aug '26

08 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45315 SUBJECT: GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119) DATE: 26/08/08 06:09:23 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 807850307 at 02:51:42 on 08 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) = 344.1 deg Decl.(2000.0) = 11.9 deg The 1 sigma statistical error radius is 2.9 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260808119/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260808119/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260808119/json View this GCN Circular online at https://gcn.nasa.gov/circulars/45315. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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