{
  "createdOn": 1777476394232,
  "eventId": "GRB 260428A",
  "submittedHow": "web",
  "circularId": 44424,
  "format": "text/plain",
  "body": "SVOM/GRM team: Chen-Wei Wang, Chao Zheng, Zheng-Hang Yu, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)\n\nSVOM/ECLAIRs team: Olivier GODET (IRAP)\n\nReport on behalf of the SVOM team:\n\nSVOM/GRM was triggered in-flight by a burst GRB 260428A (SVOM trigger reference: sb26042803) at 2026-04-28T14:20:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#44415), AstroSat (A. Goyal et al., GCN#44421) and GECAM-B (Wang et al., GCN#44423).\n\nWith the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of mutli-pulses hard spikes followed by a soft weak extended emission with a T90 of 4.1 +3.1/-2.1 s in the 15-5000 keV band.\n\nThe SVOM/GRM light curve can be found here:\nhttps://www.bursthub.cn//admin/static/svgrb260428A.png\n\nIn addition, the position of this burst, as determined by Fermi/GBM (RA = 277.0 deg, Dec = 1.9 deg, Err= 2.1 deg, GCN#44415), is located at about 100 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. \n\nWith this localization, the time-averaged spectrum from T0-1.4 to T0+8.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +0.33/-0.25 and the cutoff energy, parameterized as Epeak, is 1380 +159/-66 keV. The event fluence (10-1000 keV) in this time interval is (4.82 +0.83/-0.79)E-06 erg/cm^2. \n\nGRB 260428A falls into the Type I region in the 'Amati' relation diagram, as shown at: \nhttps://www.bursthub.cn//admin/static/svgrb260428A_amati.png \n\nWith the brightness of the prompt emission, the predicted soft X-ray afterglow [1] is shown at: \nhttps://www.bursthub.cn//admin/static/svgrb260428A_xag_pre.png\n\n\nThe 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.\n\nThe SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn) \n\n[1] Chen-Wei Wang et al. ApJ 997 353 https://doi.org/10.3847/1538-4357/ae2eae\n",
  "subject": "GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission",
  "bibcode": "2026GCN.44424....1S",
  "submitter": "Chenwei Wang at IHEP <cwwang@ihep.ac.cn>"
}