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

[vsnet-grb-info 43471] The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45255 SUBJECT: The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star DATE: 26/07/30 03:20:46 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Y. Ren (NAO, CAS), Y. F. Liang (PMO), J. W. Hu, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709277130 (EP260729a, GCN 45253) at the time of 2026-07-29T17:04:47, is likely a stellar flare associated with RX J2350.0+2659 and also confirmed by optical observation (Jelinek et al., GCN 45254). The refined analysis of the WXT data shows that the average WXT 0.5-4 keV spectrum can be fitted with an apec model. The best-fit temperature is 2.78 keV. The derived average unabsorbed 0.5-4 keV flux is 9.42 (-3.00/+7.95)×10^-11 erg/s/cm^2, corresponding to a luminosity of 1.24 (-0.45/+1.03)×10^31 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/45255. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43470] EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45254 SUBJECT: EP 260729a: Ondrejov D50 optical detection supports stellar flare origin DATE: 26/07/29 22:52:45 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny and R. Hudec (ASU CAS Ondrejov) report: We observed the position of the Einstein Probe transient EP260729a (Zhou et al., GCN 45253) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic, obtaining 19x120s r'-band exposures starting at 21:13 UT on 2026 July 29 (~4.1 h after the WXT trigger). We find no uncatalogued object in the error circle down to r>21.5 (3-sigma) in the combined image. The M4.0V high proper motion star RX J2350.0+2659 (ATLAS-RefCat2 r=13.876; Zhou et al., GCN 45253) is bright and well detected in single exposures. It appears elevated in brightness at the start of our sequence, fading over ~40 minutes. A linear fit gives an initial excess of ~0.14 mag over its catalogued magnitude, decaying at ~0.1 mag/hour. This fading excess supports the stellar flare origin of EP260729a suggested by the EP team (Zhou et al., GCN 45253). View this GCN Circular online at https://gcn.nasa.gov/circulars/45254. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43469] EP260729a: Einstein Probe detection of an X-ray transient
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45253 SUBJECT: EP260729a: Einstein Probe detection of an X-ray transient DATE: 26/07/29 18:01:14 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), G. J. Yang, J. W. Hu, C. C. Jin (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 EP260729a. The transient triggered EP-WXT (ID: 01709277130) at 2026-07-29T17:04:47 (UTC). The WXT position of the source is R.A. = 357.559 deg, DEC = 26.992 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. = 357.5308 deg, DEC = 26.9981 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/45253. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43468] EP260727a: SAO RAS optical observations
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45252 SUBJECT: EP260727a: SAO RAS optical observations DATE: 26/07/29 12:55:38 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of EP260727a (Hu et al., GCN 45235) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. We obtained 9*20 + 4*300 sec. images with Rc filter from 2026-07-27T23:31:14 to 2026-07-28T00:07:51 under mediocre weather conditions and seeing of 3".3. The OT (He et al., GCN 45234; Eyles-Ferris et al., GCN 45239; Adami et al., GCN 45243; Guziy et al., GCN 45245; also consistent with the EP-FXT position, Wu et al., GCN 45244) is clearly detected in the stacked image with the following brightness. Date UTstart t-T0 Exp. Filter Mag Err. UL (mid, h) (n*s) (3-sigma) 2026-07-27 23:31:14 3.1932 1380 Rc 21.64 +/- 0.17 22.5 Near the position of the second candidate proposed by Adami et al., (GCN 45243) we note the presence of an extended source with the coordinates (J2000.0) R. A. = 23:05:48.72; Dec. = +03:15:23.5 and brightness of R = 21.55 +/- 0.11. This preliminary photometry was given in the Vega system, calibrated against nearby SDSS stars (magnitudes converted with Lupton 2005 equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45252. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43467] GRB 260727A: AbAO and SAO RAS optical observations
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45251 SUBJECT: GRB 260727A: AbAO and SAO RAS optical observations DATE: 26/07/29 11:19:50 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), M. Zhuzhunadze (AbAO) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 260727A (Li et al., GCN 45220; Harsha. et al., GCN 45225; Cheung et al., GCN 45233; Li et al., GCN 45236; Svinkin et al., GCN 45242; Wang et al., GCN 45247) with the 0.7m AS-32 telescope of Abastumani Observatory (AbAO) and the Zeiss-1000 1m telescope of the Special Astrophysical Observatory of the RAS (SAO RAS). The observations started on 2026-07-27 at 19:15:15 UT (~0.81 days after the SVOM trigger) at AbAO. The series of 70x60 s exposures in the R-band was obtained using the CCD-photometer. The observations continued at SAO RAS starting 2026-07-28 at 00:12:38 UT (~ 1.0 days since trigger). The series of 6x300 s exposures was obtained in the Rc-band using the CCD-photometer. We performed catalog search and image subtraction (against the PS1 r-band template image) on co-add images from both observatories. The observational properties are provided further. Date UT start t-T0 Exp. Filter UL(3sigma) Site/Telescope (mid, days) (s) 2026-07-27 19:15:15 0.81092 69x60 R 20.9 AbAO/AS-32 2026-07-28 00:12:38 1.00509 6x300 Rc 22.9 SAO RAS/Zeiss-1000 No optical candidates were found in the EP-FXT error circle (Li et al., GCN 45236) up to limiting magnitude presented above. The field was also observed in optical by (Shi et al., GCN 45223; Freeberg et al., GCN 45224; Starling et al., GCN 45226; Lechapelain&Midavaine, GCN 45228; Mohan et al., GCN 45231; Bochenek et al., GCN 45240) but no candidate transients were reported. The photometry is based on nearby stars from USNO-B1.0. No correction has been made for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45251. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43466] EP260728a: EP-FXT follow-up observation
by GCN Circulars 29 Jul '26

29 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45250 SUBJECT: EP260728a: EP-FXT follow-up observation DATE: 26/07/29 07:40:29 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, J. W. Hu (NAO, CAS), H. Zhou (PMO), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the fast X-ray transient EP260728a (detected by EP-WXT, GCN 45248). The observation started at 2026-07-28 16:50:26 UTC, about 4 minutes after the WXT trigger, with an exposure time of 3.6 ks. The FXT telemetry data show that an uncatalogued source was detected within the WXT error circle at R.A. = 302.8576, DEC = -31.7138 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The 0.5-10 keV FXT spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.2 x 10^21 cm^-2. The best-fit photon index is 2.23 (-0.18/+0.18). The unabsorbed 0.5-10 keV flux is 1.22 (-0.12/+0.14) x 10^-12 erg cm^-2 s^-1. 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/45250. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43465] GRB 260726A: EP-FXT follow-up observations
by GCN Circulars 28 Jul '26

28 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45249 SUBJECT: GRB 260726A: EP-FXT follow-up observations DATE: 26/07/29 03:29:48 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Ruizhi Li (YNAO), Ziming Wang (BNU), Yifang Liang (PMO), Wenjin Xie (NAOC), Clara Plasse (HKU) report on behalf of the SVOM mission team: EP-FXT performed a follow-up observation of GRB 260726A detected by SVOM/ECLAIRs (Liang et al., GCN 45219), which also triggered Fermi/GBM (Scotton et al., GCN 45218, GCN 45246). The follow-up observation started at 2026-07-27T23:04:39 (UTC), about 23.32 hours after the SVOM-ECLAIRs trigger, with a total exposure time of around 5 ks. No X-ray counterpart was detected at the VT position (Li et al., GCN 45230). The estimated flux upper limit is 1.16 x 10^(-13) erg cm^-2 s^-1 in the 0.5–10 keV energy band (90% C.L.). Optical follow-up observations of the burst were carried out by MASTER (Lipunov et al., GCN 45221), SVOM/VT (Li et al., GCN 45230), WINTER (Mohan et al., GCN 45232) and Liverpool Telescope (Bochenek et al., GCN 45241). The Burst Advocate (BA) on shift for this alert is Rui-Zhi Li: liruizhi(a)ynao.ac.cn Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45249. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43464] EP260728a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 28 Jul '26

28 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45248 SUBJECT: EP260728a: Einstein Probe detection of a fast X-ray transient DATE: 26/07/29 02:47:29 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, J. W. Hu (NAO, CAS), H. Zhou (PMO), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260728a. The transient triggered EP-WXT (ID: 01709276975) at 2026-07-28T16:46:27 (UTC). The on-ground analysis shows the WXT position of the source is R.A. = 302.859 deg, DEC = -31.693 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The refined analysis of the WXT data shows that the event started at T0=2026-07-28T16:45:19 (UTC) and lasted for about 70 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 with a hydrogen column density of 3.1 (+2.0/-1.8)×10^21 cm^-2 and a photon index of 1.63 (+0.77/-0.72). The derived average unabsorbed 0.5-4 keV flux is 4.2 (+1.6/-0.8) x 10^-9 erg/s/cm^2. The uncertainties are at the 1 sigma confidence level for the above parameters. 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. = 302.8558 deg, DEC = -31.7161 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/45248. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43463] GRB 260727A: SVOM/GRM observation
by GCN Circulars 28 Jul '26

28 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45247 SUBJECT: GRB 260727A: SVOM/GRM observation DATE: 26/07/29 01:59:56 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Feliu Lacreu (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in flight by GRB 260727A at 2026-07-27T00:22:01.000 UTC (T0), which is also detected by SVOM/ECLAIRs (Li et al., GCN #45220), AstroSat/CZTI (Harsha K. H. et al., GCN #45225), Glowbug (Cheung et al., GCN #45233) and Konus-Wind (Svinkin et al., GCN #45242). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple broad peaks with a T90 of 53 +3/-2 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn/gcn/2026/svgrb260727A.png In addition, the position of this burst, as determined by EP/FXT (RA = 331.7702 deg, Dec = 74.5296 deg, Err = 10 arcsec; GCN #45236), is located at about 23.7 degrees from the SVOM optical axis. With this localization, the time-averaged spectrum from T0-3 to T0+70 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.64 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 81.7 +3.0/-2.7 keV. The event fluence (10-1000 keV) in this time interval is (1.352 +0.034/-0.032)E-05 erg/cm^2. The localization of GRB 260727A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn/gcn/2026/svgrb260727A_amati.png The localization of GRB 260727A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn/gcn/2026/svgrb260727A_yonetoku.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/45247. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43462] GRB 260726A: Fermi GBM Observation
by GCN Circulars 28 Jul '26

28 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45246 SUBJECT: GRB 260726A: Fermi GBM Observation DATE: 26/07/28 22:06:21 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 23:44:49.07 UT on 26 July 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260726A (trigger 806802294/260726989), which was also detected by SVOM (Liang et al. 2026, GCN 45219; Brunet et al. 2026, GCN 45229). An optical counterpart is identified by Liverpool Telescope (Bochenek et al. 2026, GCN 45241). The Fermi GBM real-time localization (GCN 45218) is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 21 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.6 to T0+23.8 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.27 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 121 +/- 6 keV. The event fluence (10-1000 keV) in this time interval is (1.32 +/- 0.10)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.2 s in the 10-1000 keV band is 1.4 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/45246. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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