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[vsnet-grb-info 42924] GRB 260601A: SVOM/GRM observation of a short burst
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44793 SUBJECT: GRB 260601A: SVOM/GRM observation of a short burst DATE: 26/06/03 07:52:54 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: Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 260601A at 2026-06-01T11:00:12.500 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44755) and GECAM-B (Yue Wang et. al., GCN #44778). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of muplti-pulses with a T90 of 0.20 +0.47/-0.09 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260601A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 15.1, Dec = 44.4, Error = 2.0, GCN #44755), is located at about 116 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-0.06 to T0+0.16 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.04 +0.15/-0.17 and the cutoff energy, parameterized as Epeak, is 899 +210/-150 keV. The event fluence (10-1000 keV) in this time interval is (3.28 +0.138/−0.13)E-06 erg/cm^2. The localization of GRB 260601A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260601A_amati.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/44793. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42923] EP260602c: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44792 SUBJECT: EP260602c: Einstein Probe detection of a fast X-ray transient DATE: 26/06/03 07:24:41 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J.Y. Cao, Z. X. Li, G. L. Huang, (IHEP, CAS), J. W. Hu, Y. Liu (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 EP260602c. The source did not trigger the WXT on-board trigger unit. A GCN Notice was sent manually (trigger ID: 13616654964). The ground analysis of the WXT data shows that the event started at T0=2026-06-02T09:06:44 (UTC) and lasted for about 200 s. The WXT position of the source is R.A. = 134.673 deg, DEC = -75.673 deg (J2000) with an uncertainty of 2.3 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 8 × 10^20 cm^-2, and a photon index of 2.14 (-0.41, +0.46). The derived average unabsorbed 0.5-4 keV flux is 1.9 (-0.5, +0.6)×10^(-10) erg/s/cm^2. A Target-of-Opportunity observation with the Follow-up X-ray Telescope (FXT) has been scheduled. 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/44792. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42922] EP260602c: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44792 SUBJECT: EP260602c: Einstein Probe detection of a fast X-ray transient DATE: 26/06/03 07:24:41 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J.Y. Cao, Z. X. Li, G. L. Huang, (IHEP, CAS), J. W. Hu, Y. Liu (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 EP260602c. The source did not trigger the WXT on-board trigger unit. A GCN Notice was sent manually (trigger ID: 13616654964). The ground analysis of the WXT data shows that the event started at T0=2026-06-02T09:06:44 (UTC) and lasted for about 200 s. The WXT position of the source is R.A. = 134.673 deg, DEC = -75.673 deg (J2000) with an uncertainty of 2.3 arcmin in radius (90% C.L. statistical and systematic). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 8 × 10^20 cm^-2, and a photon index of 2.14 (-0.41, +0.46). The derived average unabsorbed 0.5-4 keV flux is 1.9 (-0.5, +0.6)×10^(-10) erg/s/cm^2. A Target-of-Opportunity observation with the Follow-up X-ray Telescope (FXT) has been scheduled. 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/44792. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42921] GRB 260603A : SVOM/COLIBRÍ optical counterpart candidate
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44791 SUBJECT: GRB 260603A : SVOM/COLIBRÍ optical counterpart candidate DATE: 26/06/03 06:54:17 GMT FROM: Marion G <marion.guelfand(a)gmail.com> Marion Guelfand (CPPM), Alan M. Watson (UNAM), Noémie Globus (UNAM), 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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Ruizhi Li (YNAO), and Ziming Wang (BNU) report: We imaged the field of the SVOM GRB 260603A (Zhao et al., GCN Circ. 44787) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-06-03 05:39:27 to 06:02:56 UTC (from 133 seconds to 27 minutes after the trigger) and obtained 1000 seconds of simultaneous exposure in the r/z filters. The data were reduced, coadded, and analyzed with the COLIBRI ASU pipeline. The photometry was calibrated using nearby stars from the Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect an uncatalogued source consistent with the ECLAIRs 5.42 arcmin error circle (Zhao et al., GCN Circ. 44787) at: RA (J2000) = 15:32:34.55 = 233.14397 degrees Dec (J2000) = +40:01:33.3 = 40.02591 degrees The preliminary magnitudes derived for this source are: r = 19.78 +/- 0.01 z = 19.27 +/- 0.01 The source is observed to brighten and then fade. We suggest this is the counterpart of the GRB. Further observations are ongoing. 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 Observa View this GCN Circular online at https://gcn.nasa.gov/circulars/44791. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42920] EP260602a: COLIBRÍ optical observations
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44790 SUBJECT: EP260602a: COLIBRÍ optical observations DATE: 26/06/03 06:45:07 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Marion Guelfand (CPPM), Rosa L. Becerra (UNAM), 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), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), 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 EP260602a (Li et al., GCN Circ. 44770) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-03 03:38 to 05:17 UTC (from 19.45 to 21.10 hours after the trigger) and obtained 15, 30, 29, and 74 minutes of exposure in the g, r, i, and z filters, respectively. 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 detect a faint source at a position consistent with that of the counterpart reported by Xu et al. (GCN Circ. 44781). This source is not seen in Pan-STARRS DR2 or Legacy Survey DR10 (Dey et al. 2019) images. The preliminary magnitudes of the source are, after subtracting the PS images to remove the 20-mag source 3.5 arcsec to the south, are: g = 23.27 +/- 0.40 r = 23.26 +/- 0.21 i = 23.28 +/- 0.24 z = 22.98 +/- 0.39 The colors in our photometry are moderately red and do not suggest a high-redshift counterpart. Xu et al. report a very red color of VT_B - VT_R ≈ 2.0 +/- 0.3. Comparing griz photometry to VT photometry is not straightforward, but approximating VT_B ≈ g + r and VT_R ≈ i + z, we estimate much less extreme colors of VT_B - VT_R ≈ 0.13 +/- 0.32. One possible explanation for this difference is that Xu et al. observed a high-redshift or highly-reddened afterglow which has now faded, and we are observing the host or an intervening galaxy. However, the lack of detection of a corresponding source in both Pan-STARRS and Legacy Survey images argues against this. We currently do not have an explanation for this difference. 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/44790. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42919] GRB260601B/EP260601a: NOT near-infrared observations
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44789 SUBJECT: GRB260601B/EP260601a: NOT near-infrared observations DATE: 26/06/03 06:41:27 GMT FROM: liuxing(a)nao.cas.cn X. Liu, J. An, L.B. He, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu (HUST), J.P.U. Fynbo (DAWN/NBI), A. M. Kadela report (NOT): We observed the field of GRB260601B/EP260601a (Yang et al., GCN 44766; Yu et al., GCN 44767; Waratkar et al., GCN 44771; Sugita et al., 44773), using the 2.56m Nordic Optical Telescope (NOT) equipped with the NOTCam near-infrared camera. Observation started at 2026-06-03 00:53:22 UT, i.e., 29.67 hr post-burst, and 25x60s J-band frames were obtained. The previously reported optical counterpart (Liu et al., GCN 44764; Guelfand et al., GCN 44765; Li et al., GCN 44769) was detected in our stacked image with a brightness of J = 20.7 +/- 0.1 (Vega) at a median time of 29.94 hr post-trigger, calibrated with the 2MASS catalog and not corrected for Galactic extinction. We acknowledge the excellent support from the NOT staff, in particular A. M. Kadela. View this GCN Circular online at https://gcn.nasa.gov/circulars/44789. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42918] SVOM GRB260603.23: Global MASTER-Net observations report
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44788 SUBJECT: SVOM GRB260603.23: Global MASTER-Net observations report DATE: 26/06/03 06:30:40 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) was pointed to the SVOM GRB260603.23 (trigger No 1780465035,15h 32m 48.05s , +40d 06m 06.5s, R=0.1222) errorbox 6 sec after notice time and 1357 sec after trigger time at 2026-06-03 05:59:52 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 9 deg. The sun altitude is -33.5 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the SVOM GRB260603.23 errorbox 241 sec after notice time and 1593 sec after trigger time at 2026-06-03 06:03:48 UT, with upper limit up to 16.4 mag. The observations began at zenith distance = 81 deg. The sun altitude is -67.9 deg. The galactic latitude b = 54 deg., longitude l = 64 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3357257 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1418 | 2026-06-03 05:59:52 | MASTER-OAGH | (15h 33m 43.57s , +40d 02m 45.7s) | P- | 120 | 16.8 | 1546 | 2026-06-03 06:02:01 | MASTER-OAGH | (15h 33m 43.89s , +40d 01m 28.2s) | P- | 120 | 17.1 | 1624 | 2026-06-03 06:03:48 | MASTER-OAFA | (15h 32m 34.31s , +40d 16m 14.5s) | C | 60 | 15.8 | 1684 | 2026-06-03 06:03:48 | MASTER-OAFA | (15h 32m 34.31s , +40d 16m 14.2s) | C | 180 | 15.9 | Coadd 1676 | 2026-06-03 06:04:10 | MASTER-OAGH | (15h 33m 46.25s , +40d 02m 43.1s) | P- | 120 | 17.4 | 1689 | 2026-06-03 06:04:54 | MASTER-OAFA | (15h 32m 34.09s , +40d 16m 14.9s) | C | 60 | 15.8 | 1755 | 2026-06-03 06:05:59 | MASTER-OAFA | (15h 32m 33.86s , +40d 16m 15.8s) | C | 60 | 15.5 | 1804 | 2026-06-03 06:06:18 | MASTER-OAGH | (15h 33m 41.29s , +40d 02m 06.6s) | P- | 120 | 17.4 | 1824 | 2026-06-03 06:07:08 | MASTER-OAFA | (15h 32m 33.78s , +40d 16m 13.7s) | C | 60 | 15.6 | 1884 | 2026-06-03 06:07:08 | MASTER-OAFA | (15h 32m 33.73s , +40d 16m 14.9s) | C | 180 | 15.9 | Coadd 1890 | 2026-06-03 06:08:14 | MASTER-OAFA | (15h 32m 33.62s , +40d 16m 13.5s) | C | 60 | 15.5 | 1955 | 2026-06-03 06:09:20 | MASTER-OAFA | (15h 32m 33.33s , +40d 16m 14.8s) | C | 60 | 15.1 | 2087 | 2026-06-03 06:11:32 | MASTER-OAFA | (15h 32m 32.85s , +40d 16m 17.2s) | C | 60 | 14.9 | 2285 | 2026-06-03 06:14:49 | MASTER-OAFA | (15h 32m 32.35s , +40d 16m 15.8s) | C | 60 | 12.8 | 2416 | 2026-06-03 06:17:01 | MASTER-OAFA | (15h 32m 31.97s , +40d 16m 14.5s) | C | 60 | 12.7 | 2482 | 2026-06-03 06:18:07 | MASTER-OAFA | (15h 32m 31.82s , +40d 16m 13.7s) | C | 60 | 12.8 | 2542 | 2026-06-03 06:18:07 | MASTER-OAFA | (15h 32m 31.54s , +40d 16m 17.3s) | C | 180 | 15.8 | Coadd 2548 | 2026-06-03 06:19:12 | MASTER-OAFA | (15h 32m 31.62s , +40d 16m 12.7s) | C | 60 | 15.1 | 2614 | 2026-06-03 06:20:18 | MASTER-OAFA | (15h 32m 31.86s , +40d 16m 06.4s) | C | 60 | 16.0 | 2679 | 2026-06-03 06:21:23 | MASTER-OAFA | (15h 32m 31.35s , +40d 16m 10.4s) | C | 60 | 15.9 | 2744 | 2026-06-03 06:22:29 | MASTER-OAFA | (15h 32m 30.72s , +40d 16m 16.0s) | C | 60 | 16.4 | 2810 | 2026-06-03 06:23:35 | MASTER-OAFA | (15h 32m 30.85s , +40d 16m 11.4s) | C | 60 | 16.3 | 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/44788. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42917] GRB 260603A: SVOM detection of a burst
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44787 SUBJECT: GRB 260603A: SVOM detection of a burst DATE: 26/06/03 06:28:01 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Donghua ZHAO, Wenjin Xie (NAOC), Ruizhi Li (YNAO), Ziming Wang (BNU) report on behalf of the SVOM mission team: At 2026-06-03T05:38:16 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260603A (SVOM burst-id sb26060303). 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 13 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 15.29 in the [5-20] keV energy band over a time window of 81.92 seconds starting at 2026-06-03T05:37:55. The localization of the best alert is R.A., Dec. 233.1366,40.0801 degrees: R.A. (J2000) = 15h32m32.79s Dec. (J2000) = 40d04m48.22s with a 90% confidence level (C.L.) radius of 5.42 arcmin (including systematic error of 2 arcmin added in quadrature). One high proper motion star named TYC 3055-1389-1 is at 194.45 arcsec away. Due to a ToO-EX in performance, no immediate slew was performed on this burst. 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 Ruizhi 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/44787. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42916] EP260602b: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44786 SUBJECT: EP260602b: Einstein Probe detection of a fast X-ray transient DATE: 26/06/03 06:14:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. W. Hu (NAO, CAS), Z. X. Li, G. L. Huang, J. Y. Cao (IHEP, CAS), Y. Liu (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 EP260602b. The transient triggered EP-WXT (ID: 01709266414) at 2026-06-02T17:54:02 (UTC). The WXT position of the source is R.A. = 273.487 deg, DEC = 7.595 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The refined analysis of the WXT data shows that the event was detected at R.A. = 273.483 deg, DEC = 7.579 deg (J2000) with an uncertainty of 2.6 arcmin in radius. The event started at T0=2026-06-02T17:53:12 (UTC), and lasted for about 60 s. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.9 × 10^21 cm^-2, and a photon index of 1.36 (-0.80, +0.87). The derived average unabsorbed 0.5-4 keV flux is 1.8 (-0.6, +0.7)×10^(-9) erg/s/cm^2. The optical counterpart of EP260602b was reported by He et al. (GCN 44780). No autonomous follow-up observation with Follow-up X-ray Telescope (FXT) was performed. A Target-of-Opportunity observation with the FXT has been scheduled. 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/44786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42915] GRB 260601B/EP260601a: Insight-HXMT detection
by GCN Circulars 03 Jun '26

03 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44785 SUBJECT: GRB 260601B/EP260601a: Insight-HXMT detection DATE: 26/06/03 06:12:43 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong, Cheng-Kui Li, and Chao Zheng report on behalf of the Insight-HXMT team: At 2026-06-01T19:12:49.900 (T0), Insight-HXMT/HE detected the possible long duration Type I burst GRB 260601B/EP260601a, which is also detected by GECAM-B (Yu et al., GCN #44767; Wang et al., GCN #44768), NuSTAR (Waratkar et al., GCN #44771), CGBM (S. Sugita et al., GCN #44773) and EP (Yang et al., GCN #44766). The Insight-HXMT/HE light curve mainly consists of a possible precursor and then a short pulse followed by a long emission with a T90 of 76.0 +4.5/-4.0 s. The total counts from this burst is 175433 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260601B.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/44785. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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