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[vsnet-grb-info 43271] GRB 260629A: Fermi GBM Final Real-time Localization
by GCN Circulars 29 Jun '26

29 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45056 SUBJECT: GRB 260629A: Fermi GBM Final Real-time Localization DATE: 26/06/29 15:19:19 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 15:06:58 UT on 29 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260629A (trigger 804438423.955606 / 260629630). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 146.1, Dec = 70.6 (J2000 degrees, equivalent to J2000 09h 44m, 70d 35'), with a statistical uncertainty of 10.5 degrees. The angle from the Fermi LAT boresight is 49.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260629630/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260629630/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260629630/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45056. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43270] Fermi GRB 260628A: Global MASTER-Net observations report
by GCN Circulars 29 Jun '26

29 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45055 SUBJECT: Fermi GRB 260628A: Global MASTER-Net observations report DATE: 26/06/29 03:33:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) started inspect of the Fermi GRB 260628A ( Fermi GBM team, GCN 45053) errorbox 19512 sec after notice time and 19564 sec after trigger time at 2026-06-29 03:17:28 UT, with upper limit up to 15.9 mag. Observations started at twilight. The observations began at zenith distance = 81 deg. The sun altitude is -9.9 deg. The galactic latitude b = -26 deg., longitude l = 39 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3405318 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 19595 | 2026-06-29 03:17:28 | MASTER-OAGH | (19h 41m 35.39s , +00d 26m 15.1s) | C | 60 | 14.6 | 19821 | 2026-06-29 03:21:14 | MASTER-OAGH | (19h 41m 18.87s , -01d 27m 54.5s) | C | 60 | 15.0 | 19821 | 2026-06-29 03:21:14 | MASTER-OAGH | (19h 35m 27.78s , -00d 49m 53.7s) | C | 60 | 14.5 | 19901 | 2026-06-29 03:22:35 | MASTER-OAGH | (19h 43m 03.30s , +02d 19m 13.8s) | C | 60 | 15.4 | 20056 | 2026-06-29 03:25:10 | MASTER-OAGH | (19h 47m 54.90s , +02d 57m 54.9s) | C | 60 | 14.9 | 20056 | 2026-06-29 03:25:10 | MASTER-OAGH | (19h 53m 46.15s , +02d 19m 54.0s) | C | 60 | 15.4 | 20137 | 2026-06-29 03:26:30 | MASTER-OAGH | (19h 45m 51.59s , +04d 13m 03.3s) | C | 60 | 15.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/45055. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43269] EP260628a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 29 Jun '26

29 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45054 SUBJECT: EP260628a: EP-WXT detection of a fast X-ray transient DATE: 26/06/29 03:22:43 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. Mao, H. N. Yang (NAO, CAS), C. Y. Dai(NJU), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient, designated EP260628a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient was identified in the telemetry data. The transient started at 2026-06-28T17:08:08 (UTC) and lasted for about 30s, with a peak flux of ~ 7 x 10^(-9) erg cm^-2 s^-1 in 0.5-4 keV. The position of the transient is R.A. = 312.9884 deg, Dec. = -34.3748 (J2000), with an uncertainty radius of 2.8 arcmin in radius (90% confidence level, including both statistical and systematic uncertainties). There are no known X-ray sources in the WXT error circle. The average WXT 0.5-4 keV spectrum can be fitted by an absorbed power-law model with a fixed Galactic hydrogen column density of 4.86×10^20 cm^-2 and a photon index of 0.67 (-0.52/+0.52). The derived average unabsorbed 0.5-4 keV flux is 1.87 (-0.54/+0.71) x 10^(-9) erg cm^-2 s^-1. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT will be arranged. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/45054. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43268] GRB 260628A: Fermi GBM Final Real-time Localization
by GCN Circulars 28 Jun '26

28 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45053 SUBJECT: GRB 260628A: Fermi GBM Final Real-time Localization DATE: 26/06/28 22:03:44 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 21:51:24 UT on 28 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260628A (trigger 804376289.020238 / 260628911). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 308.2, Dec = -6.9 (J2000 degrees, equivalent to J2000 20h 32m, -6d 54'), with a statistical uncertainty of 14.3 degrees. The angle from the Fermi LAT boresight is 63.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260628911/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260628911/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260628911/… View this GCN Circular online at https://gcn.nasa.gov/circulars/45053. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43267] The EP-WXT trigger 01709272671 is likely a flaring star
by GCN Circulars 28 Jun '26

28 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45052 SUBJECT: The EP-WXT trigger 01709272671 is likely a flaring star DATE: 26/06/28 02:08:13 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Chen (SYSU), K. J. Zhang, D. Zhu (YNU), Y. J. Yi (BNU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709272671 at the time of 2026-06-27T17:53:04 (UTC), is likely a stellar flare associated with RX J1942.2-2045. The estimated flux of the flare is around 1.6 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4.8 x 10^(30) 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/45052. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43266] EP260626a: further Liverpool Telescope optical upper limits
by GCN Circulars 27 Jun '26

27 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45051 SUBJECT: EP260626a: further Liverpool Telescope optical upper limits DATE: 26/06/27 17:25:38 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of EP260626a (Chen et al., GCN 45047; Chen et al., GCN 45050) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 8x150s exposures in SDSS r and z filters, starting at 2026-06-27 01:59:23 UT, approximately 20.57 hours after EP trigger. The stacked exposures were subtracted from PanSTARRS reference imaging using custom PSF-matching image subtraction code utilising Swarp, SourceExtractor, and PSFex. We do not detect any new sources in the error EP/WXT region (Chen et al., GCN 45047), including at the position of the uncatalogued X-ray source reported by Chen et al. (GCN 45047), down to 3 sigma upper limits of r> 23.44 and z> 22.94. This is consistent with upper limits from Eyles-Ferris et al. (GCN 45048) and Magnani et al. (GCN 45049). The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43265] EP260626a: EP-FXT follow-up observation
by GCN Circulars 27 Jun '26

27 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45050 SUBJECT: EP260626a: EP-FXT follow-up observation DATE: 26/06/27 15:28:42 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Chen (SYSU), K. J. Zhang, D. Zhu (YNU), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP260626a (J. P. Chen et al., GCN 45047) approximately 10.8 hours after the WXT detection, with an exposure time of 6.1 ks. An uncatalogued X-ray source was detected within the WXT error circle at R.A. = 277.4479, Dec. = 21.2498 (J2000), with a positional uncertainty of 10.0 arcsec (radius, 90% C.L. statistical and systematic). The FXT spectrum can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 2.04 x 10^21 cm^-2 and a photon index of 2.13 (+0.6, -0.6). The derived unabsorbed 0.5-10 keV flux is approximately 9.3 (+4.5, -2.1) x 10^-14 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No optical counterpart has been detected (R. A. J. Eyles-Ferris et al., GCN 45048; Francesco Magnani et al., GCN 45049). 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/45050. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43264] EP260526a: COLIBRÍ optical upper limit
by GCN Circulars 27 Jun '26

27 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45049 SUBJECT: EP260526a: COLIBRÍ optical upper limit DATE: 26/06/27 10:31:22 GMT FROM: F. Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Fredd Sánchez Álvarez (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), 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), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP 260526a (J.P. Chen et al., GCN Circ. 45047) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-27T07:56:30 to 09:19:26 UTC (from 26.5 to 27.9 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r, z filters. The data were reduced, coadded, and analysed with the COLIBRÍ 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. In the stacked image, we do not detect any new source at the WXT source position (J.P. Chen et al., GCN Circ. 45047) down to the following 3-sigma limit: r > 23.87 z > 23.15 This upper limit is consistent with the one reported by R. A. J. Eyles-Ferris et al., GCN Circ. 45048. 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/45049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43263] EP260626a: Liverpool Telescope upper limits
by GCN Circulars 27 Jun '26

27 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45048 SUBJECT: EP260626a: Liverpool Telescope upper limits DATE: 26/06/27 08:25:50 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), report on behalf of a larger collaboration: We observed the field of the Einstein Probe fast X-ray transient EP260626a (Chen et al., GCN 45047) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150 s exposures in each of the SDSS r’ and z’ filters starting at 2026-06-27 02:24:23 UT, approximately 21 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. Within the EP/WXT localisation, we detect no new sources in any of the bands. We derive the following 3-sigma upper limits for our stacked images. Our photometry is calibrated to PanSTARRS and not corrected for Galactic extinction. | t_mid (hours) | Filter | AB magnitude | | ------------- | ------ | ------------ | | 21.13 | r’ | >22.89 | | 21.44 | z’ | >22.37 | View this GCN Circular online at https://gcn.nasa.gov/circulars/45048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43262] EP260626a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 26 Jun '26

26 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45047 SUBJECT: EP260626a: EP-WXT detection of a fast X-ray transient DATE: 26/06/26 15:13:06 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J.P. Chen (SYSU), K. J. Zhang, D. Zhu (YNU), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient, designated EP260626a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient was identified in the telemetry data. The transient was detected in the WXT observation starting at 2026-06-26T05:25:04 (UTC). A significant flare was detected in the source light curve, which started before the beginning of the observation and ended approximately 100 seconds after the start of the observation. The position of the transient is R.A. = 277.4417 deg, Dec. = 21.2403 deg (J2000), with an uncertainty radius of 2.7 arcmin in radius (90% confidence level, including both statistical and systematic uncertainties). There are no known X-ray sources in the WXT error circle. The average WXT 0.5-4 keV spectrum can be fitted by an absorbed power-law model with a fixed Galactic hydrogen column density of 2.04×10^21 cm^-2 and a photon index of 1.93 (-0.4/+0.42). The derived average unabsorbed 0.5-4 keV flux is 8.02 (-1.7/+2.1) x 10^(-11) erg cm^-2 s^-1. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT will be arranged. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/45047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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