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[vsnet-grb-info 42368] The EP-WXT trigger 01709259773 is likely a flaring star
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44247 SUBJECT: The EP-WXT trigger 01709259773 is likely a flaring star DATE: 26/04/09 12:34:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S.Q. Jiang (NAO, CAS), G. L. Huang, Z. X. Li, J. Y. Cao (IHEP, CAS), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709259773 at the time of 2026-04-09T11:45:11, is likely a stellar flare associated with 1RXS J121842.8-060921. The estimated flux of the flare is around 1.4 × 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 8.6 × 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/44247. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42367] GRB 260407A: GECAM-A detection
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44246 SUBJECT: GRB 260407A: GECAM-A detection DATE: 26/04/09 11:19:26 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Shao-Lin Xiong, Peng Zhang, Yan-Qiu Zhang, Chen-Wei Wang (IHEP) report on behalf of the GECAM team: GECAM-A detected a long burst, GRB 260407A, at 2026-04-07T09:11:07.950 UTC (denoted as T0), which was also observed by Fermi GBM (GCN #44226), Glowbug (C.C. Cheung et al., GCN #44237), CALET (M. L. Cherry et al., GCN #44242) and Insight-HXMT/HE (Hao-Xuan Guo et al., GCN #44245). According to the GECAM-A light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 19.5 +4.5/-6.5 s. The GECAM-A light curve can be found here: https://www.bursthub.cn//admin/static/gecamagrb260407A.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (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/44246. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42366] GRB 260407A: Insight-HXMT/HE detection
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44245 SUBJECT: GRB 260407A: Insight-HXMT/HE detection DATE: 26/04/09 11:05:54 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-07T09:11:07.000 (T0), Insight-HXMT/HE detected a long burst, GRB 260407A, which is also detected by Fermi GBM (GCN #44226), Glowbug (C.C. Cheung et al., GCN #44237) and CALET (M. L. Cherry et al., GCN #44242). The Insight-HXMT/HE light curve mainly consists of a single pulse with a total duration (T90) of 23.5 +16/-9 s. The 1s peak rate, measured from T0+0.25 s, is 493 cnts/sec. Insight-HXMT/HE detected a total of 4651 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260407A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE 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://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44245. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42365] EP260409a: SVOM/VT optical upper limits
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44244 SUBJECT: EP260409a: SVOM/VT optical upper limits DATE: 26/04/09 09:55:42 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. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations of EP260409a triggered by Einstein Probe (Jiang et al., GCN 44240). The observation started at 2026-04-09T01:35:09 UTC, approximately 1.28 hours post trigger, in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No uncatalogued sources were detected within the error box of EP-WXT (Jiang et al., GCN 44240), compared to the Legacy Survey. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | 3 sigma upper limit 3.04 hr VT_B 106*50 sec > 23.7 mag 3.04 hr VT_R 101*50 sec > 23.6 mag Our non-detection is consistent with the result from COLIBRÍ (Globus et al., GCN 44242). 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/44244. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42364] EP260409a: COLIBRÍ optical upper limits
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44243 SUBJECT: EP260409a: COLIBRÍ optical upper limits DATE: 26/04/09 04:04:15 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Marion Guelfand (CPPM), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), 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) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260409a (Jiang et al., GCN Circ. 44240) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-09 02:56 to 03:41 (from 2.6 to 3.4 hours after the trigger) and obtained 34 min of simultaneous exposure in the r and z filters. The data were reduced and coadded with the 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. In the stacked image, we do not detect any new source at the FXT source position down to the following 5-sigma limit: r > 23.14, z > 21.84. 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/44243. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42363] GRB 260407A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44242 SUBJECT: GRB 260407A: CALET Gamma-Ray Burst Monitor detection DATE: 26/04/09 03:43:44 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> M. L. Cherry (LSU), 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), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 260407A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 44226; Glowbug gamma-ray detection: Cheung et al., GCN Circ 44237) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:11:06.11 UTC on 7 April 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1459588274/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse that starts at T-0.5 sec, peaks at T+1.6 sec, and ends at T+27.1 sec. The T90 and T50 durations measured by the SGM data are 22.6 +/- 5.0 sec and 7.0 +/- 1.0 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1459588274 The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44242. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42362] EP260409a: Global MASTER-Net observations report
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44241 SUBJECT: EP260409a: Global MASTER-Net observations report DATE: 26/04/09 02:00:29 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), C.Francile, 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260409a ( EP Team et al., GCN 44240) errorbox 2305 sec after trigger time at 2026-04-09 00:56:46 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 36 deg. The sun altitude is -33.7 deg. The galactic latitude b = 49 deg., longitude l = 273 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3241458 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 2335 | 2026-04-09 00:56:46 | MASTER-OAFA | (11h 31m 41.72s , -09d 16m 57.1s) | C | 60 | 19.5 | 2401 | 2026-04-09 00:57:52 | MASTER-OAFA | (11h 31m 41.64s , -09d 16m 56.1s) | C | 60 | 19.7 | 2467 | 2026-04-09 00:58:58 | MASTER-OAFA | (11h 31m 41.57s , -09d 16m 55.4s) | C | 60 | 19.6 | 2533 | 2026-04-09 01:00:04 | MASTER-OAFA | (11h 31m 41.51s , -09d 16m 54.5s) | C | 60 | 19.7 | 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/44241. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42361] EP260409a: Einstein Probe detection of an X-ray transient
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44240 SUBJECT: EP260409a: Einstein Probe detection of an X-ray transient DATE: 26/04/09 01:55:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S. Q. Jiang (NAO, CAS), G. L. Huang, Z. X. Li, J. Y. Cao (IHEP, CAS), W. D. Zhang (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 EP260409a. The transient triggered EP-WXT (ID: 01709259735) at 2026-04-09T00:18:21 (UTC). The WXT position of the source is R.A. = 172.895 deg, DEC = -9.348 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. = 172.9080 deg, DEC = -9.3442 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/44240. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42360] EP260321a: VLA radio detection
by GCN Circulars 09 Apr '26

09 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44239 SUBJECT: EP260321a: VLA radio detection DATE: 26/04/09 01:06:49 GMT FROM: todwyer1(a)jh.edu Tanner O'Dwyer (JHU), Alessandra Corsi (JHU), Gokul Srinivasaragavan (UMD), S. Bradley Cenko (NASA GSFC), Shreya Anand (Stanford.U), Anna Ho (Cornell), Jesper Sollerman (U.Stockholm), Bei Zhou (FemiLab & U.Chicago), Marc Kamionkowski (JHU), Jillian Rastinejad (UMD) We observed the field of EP260321a (Huang et al., GCN 44068) with the Karl G. Jansky Very Large Array (VLA) in its A-configuration. Our observations were conducted at about 13.6 days post trigger at a nominal central frequency of 6 GHz. We report the detection of a radio source with a S/N of about 4 at a position compatible with that of SN 2026gzf (Corcoran et al., GCN 44105, Rastinejad et al., GCN 44107). Our image RMS is about 5 uJy. Further observations are planned to also evaluate potential contribution of the host galaxy to the observed emission. View this GCN Circular online at https://gcn.nasa.gov/circulars/44239. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42359] GRB 260404A: Fermi GBM Final Localization
by GCN Circulars 08 Apr '26

08 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44238 SUBJECT: GRB 260404A: Fermi GBM Final Localization DATE: 26/04/08 19:07:24 GMT FROM: atrigg2(a)lsu.edu The Fermi GBM team reports the detection of a likely SHORT GRB "At 23:57:08.96 UT on 04 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260404A (trigger 797039833/260404998). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 165.79, Dec = -48.56 (J2000 degrees, equivalent to J2000 11h 03m, -48d 33'), with a statistical uncertainty of 18.12 degrees. The angle from the Fermi LAT boresight is 113 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260404998/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260404998/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260404998/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44238. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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