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[vsnet-grb-info 43582] GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45358 SUBJECT: GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5 DATE: 26/08/11 18:19:29 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, O. Godet, S. Guillot, L. Bouchet, J.-L. Atteia (IRAP), T. Maiolino (LUMP), D. Turpin, S. Schanne (CEA) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected GRB 260317A, also detected by Fermi/GBM (GCN 44041), starting at 2026-03-17T20:01:51.940 UTC (T0), through an offline targeted search with the event-by-event data downloaded via the X-band ground station. The burst was detected within several timescales and energy ranges. The best detection is obtained by the image trigger with a signal-to-noise ratio of 5.4 within 8-50 keV over a time window of 0.04 s starting at T0. This event was not detected onboard because it was too faint and too short. The ECLAIRs lightcurve shows a multi-peaked structure lasting around 0.04 s. The localization of the source is RA, Dec =280.383, -5.301 degrees: RA (J2000) = 18h41m32s Dec (J2000) = -05d18m04s with a 90% C.L. radius of 14.3 arcmin (including systematic error of 2 arcmin added in quadrature). This localization is broadly consistent with that reported by Fermi/GBM (GCN 44041). The angular separation between the two positions is 27.5 degrees, which is compatible with the 13.33 degrees 1-sigma statistical uncertainty of the GBM localization. The time-averaged spectrum from T0 to T0+0.04 s in the 5-120 keV is well fitted by a power law with a photon index of 1.1+/-0.2 and a corresponding 4-120 keV fluence of (6+/-1)e-8 erg/cm^2. Given the proximity (22 arcmin) of GRB 260317A to the magnetar 1E 1841-04.5 (also named PSR J1841−0456), and the possibly underestimated ECLAIRs positional uncertainties due to the very short duration of the burst, it is possible that GRB 260317A is actually a magnetar short burst. All quoted errors are at the 68% confidence level. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang(a)cnrs.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45358. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43581] EP2608012a: Einstein Probe detection of an X-ray transient
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45362 SUBJECT: EP2608012a: Einstein Probe detection of an X-ray transient DATE: 26/08/12 12:00:11 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Tian-Yu Liu, H. R. Ren, G. J. Yang and H. Sun (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 EP260812a. The transient triggered EP-WXT (ID: 01709278114) at 2026-08-12T11:21:01 (UTC). The WXT position of the source is R.A. = 311.450 deg, DEC = 14.142 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. = 311.4377 deg, DEC = 14.1600 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/45362. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43580] GRB 260809A: SAO RAS optical observations
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45361 SUBJECT: GRB 260809A: SAO RAS optical observations DATE: 26/08/12 11:58:37 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), N. Pankov (IKI), A. Pozanenko (IKI), A. Volnova (IKI), O. Spiridonova (SAO RAS) report on behalf of GRB follow-up team We observed the field of the GRB 260809A discovered by the SVOM (Brunet et al., GCN 45331), also detected by EP-FXT (Sun et al., GCN 45344) with the Zeiss-1000, SAO RAS 1-m telescope + CCD photometer on 2026-08-09T23:20:36--2026-08-10T00:49:19 UT (t_mid = 9.1234 hours). The OT (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339; Izzo, Saccardi and Corcoran, GCN 45340; Basa et al., GCN 45342) is clearly detected in our stacked image. Details of the observation are the following. Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-08-09 23:20:36 0.38014 14*300 Rc 22.60 +/- 0.17 23.4 This preliminary photometry (Vega) is based on nearby SDSS stars (Lupton 2005 transformation) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45361. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43579] GRB 260808B: SAO RAS optical observations
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45360 SUBJECT: GRB 260808B: SAO RAS optical observations DATE: 26/08/12 11:55:25 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of the GRB 260808B discovered by the SVOM (Bouchet et al., GCN 45316; Brunet et al., GCN 45333), also detected by EP-FXT (Wang et al., GCN 45322) with the Zeiss-1000, SAO RAS 1-m telescope + CCD photometer. The observations were carried out on August 9, 00:11:49--00:38:47 UT. We obtained 5 x 300 sec images in Rc band. The OT (Turpin et al., GCNs 45317; 45318; Li et al. GCN 45320; Adami et al., GCN 45323; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek and Perley, GCN 45330; Basa et al., GCN 45341; Burkhonov et al., GCN 45352; Li et al. GCN 45359) is clearly detected in our stacked image. Details of the observation are the following. Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-08-09 00:11:49 0.41968 5*300 Rc 22.44 +/- 0.13 23.2 This preliminary photometry (Vega) is based on nearby SDSS stars (Lupton 2005 transformation) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45360. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43578] GRB 260808B: SVOM/VT optical re-brightening at day 3
by GCN Circulars 12 Aug '26

12 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45359 SUBJECT: GRB 260808B: SVOM/VT optical re-brightening at day 3 DATE: 26/08/12 09:56:46 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) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations of GRB 260808B (sb26080812; Bouchet et al., GCN 45316; Brunet et al., GCN 45333) on 10 and 11 August 2026. The two epochs correspond to mid-times of 1.45 d and 2.94 d post-trigger, with simultaneous exposures acquired in the VT_B (400–650 nm) and VT_R (650–1000 nm) channels. The afterglow (Turpin et al., GCN 45318; Li et al., GCN 45320; Wang et al., GCN 45322; Adami et al., GCN 45323; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek et al., GCN 45330; Mohan et al., GCN 45334; Basa et al., GCN 45341; Burkhonov et al., GCN 45352) was still detected at these two epochs and exhibited rebrightening in both channels on 11 August 2026. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 2.94 d VT_B 78*80 s 21.9 +/- 0.2 mag 2.94 d VT_R 80*70 s 21.3 +/- 0.2 mag More observations for this burst 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/45359. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43577] GRB 260317A: SVOM/ECLAIRs detection through offline targeted search
by GCN Circulars 11 Aug '26

11 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45358 SUBJECT: GRB 260317A: SVOM/ECLAIRs detection through offline targeted search DATE: 26/08/11 18:19:29 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, O. Godet, S. Guillot, L. Bouchet (IRAP), T. Maiolino (LUMP), D. Turpin, S. Schanne (CEA) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected GRB 260317A, also detected by Fermi/GBM (GCN 44041), starting at 2026-03-17T20:01:51.940 UTC (T0), through an offline targeted search with the event-by-event data downloaded via the X-band ground station. The burst was detected within several timescales and energy ranges. The best detection is obtained by the image trigger with a signal-to-noise ratio of 5.4 within 8-50 keV over a time window of 0.04 s starting at T0. This event was not detected onboard because it was too faint and too short. The ECLAIRs lightcurve shows a multi-peaked structure lasting around 0.04 s. The localization of the source is RA, Dec =280.383, -5.301 degrees: RA (J2000) = 18h41m32s Dec (J2000) = -05d18m04s with a 90% C.L. radius of 14.3 arcmin (including systematic error of 2 arcmin added in quadrature). This localization is broadly consistent with that reported by Fermi/GBM (GCN 44041). The angular separation between the two positions is 27.5 degrees, which is compatible with the 13.33 degrees 1-sigma statistical uncertainty of the GBM localization. The time-averaged spectrum from T0 to T0+0.04 s in the 5-120 keV is well fitted by a power law with a photon index of 1.1+/-0.2 and a corresponding 4-120 keV fluence of (6+/-1)e-8 erg/cm^2. Given its short duration and location in the Galactic plane (latitude b ~ -0.22 deg), this event is a possible magnetar burst. All quoted errors are at the 68% confidence level. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang(a)cnrs.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45358. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43576] GRB 260806A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 11 Aug '26

11 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45357 SUBJECT: GRB 260806A: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/11 12:40:04 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Ricciarini (U of Florence), 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), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260806A at 07:26:59.65 UTC on 6 August 2026 (trigger #1470036404; https://cgbm.calet.jp/cgbm_trigger/flight/1470036404/index.html) A CGBM Notice was distributed in near real time. This event was also reported by Glowbug (Cheung et al., GCN #45348). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T+1.7 s, peaking at T+6.9 s, and ending at T+64.6 s. The T90 and T50 durations measured with the SGM data are 55.7 +/- 3.1 s and 34.9 +/- 11.5 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1470036404/ 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/45357. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43575] GRB 260808A: GECAM-B observation
by GCN Circulars 11 Aug '26

11 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45356 SUBJECT: GRB 260808A: GECAM-B observation DATE: 26/08/11 10:49:01 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Ren-Yang Zhao, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260808A, at 2026-08-08T02:51:45.500 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45313), NuSTAR (G. Waratkar et.al., GCN#45327) and CGBM (M.L. Cherry et.al., GCN#45347). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 14 +/-2 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//gcn/2026/gecambgrb260808A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/45356. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43574] GRB 260807A: SVOM/ECLAIRs refined analysis
by GCN Circulars 11 Aug '26

11 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45355 SUBJECT: GRB 260807A: SVOM/ECLAIRs refined analysis DATE: 26/08/11 10:07:50 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, L. Bouchet (IRAP), R.-Z. Li (YNAO), W.-J. Xie, C. Wu (NAOC) report on behalf of the SVOM/ECLAIRs team: Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of the possible faint burst GRB 260807A (SVOM burst-id sb26080703, GCN 45308, trigger time T0 = 2025-08-07T11:00:20 UTC). The burst that triggered ECLAIRs shows a multiple peak light curve, and is detected from T0-20 s to T0 in the 8-120 keV energy band. The time-averaged spectrum from T0-20 s to T0 in the 8-120 keV is well fitted by a power-law model with a photon index of 0.7+/-0.3 and a corresponding 4-120 keV fluence of (1.4+/-0.3)e-6 erg/cm^2. All the quoted errors are at the 68% confidence level. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Hui Yang (IRAP) (hui.yang(a)cnrs.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45355. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43573] EP260806a: MAO/AZT-22 optical observations
by GCN Circulars 11 Aug '26

11 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45354 SUBJECT: EP260806a: MAO/AZT-22 optical observations DATE: 26/08/11 10:04:26 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> B.Abidkhanov, Y. Rajabov, O. Burkhonov, S. Ehgamberdiev, Y. Tillayev (UBAI), A. Shaymanov, T. Boyqobilov (Maidanak Observatory/UBAI) M. Coughlin (UMN), P. Hello (IJCLAB), S. Antier (IJCLAB), M. Pillas (IAP), and S. Karpov (FZU) report on behalf of UBAI team and GRANDMA collaboration. We observed the field of EP260806a (Li et al., GCN Circ. 45299) with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2026-08-10 at 22:51:39 UTC and obtained 8x300 s exposure in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). All the data have been reduced by a single data processing pipeline, STDWeb (Karpov 2025). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. For template subtraction were used Pans-STARRS DR2 catalog. Our measurements in Vega magnitude system and the data has not corrected for the Galactic extinction. After subtracting the template, we clearly detected the optical counterpart (He et al., GCN 45300; de Ugarte Postigo et al., GCN 45302; Eyles-Ferris et al., GCN 45303; Ma et al., GCN 45304; de Ugarte Postigo et al., GCN 45306; Anumarlapudi et al., GCN 45312) Preliminary photometry is as follows: Date UTstart Exptime Filter OT Err. UL SNR Site/Telescope (nxs) 2026-08-10 22:51:39 8x300 R 18.16 0.01 23.17 132 MAO/AZT-22 Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io). View this GCN Circular online at https://gcn.nasa.gov/circulars/45354. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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