{
  "circularId": 44268,
  "format": "text/plain",
  "submitter": "Chenwei Wang at IHEP <cwwang@ihep.ac.cn>",
  "createdOn": 1775924674753,
  "bibcode": "2026GCN.44268....1S",
  "subject": "GRB 260411B: SVOM/GRM observation of a long burst",
  "body": "SVOM/GRM team: Chen-Wei Wang, Chao Zheng, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)\n\nSVOM/ECLAIRs team: Frédéric Daigne (IAP)\n\nReport on behalf of the SVOM team:\n\nSVOM/GRM was triggered in-flight GRB 260411B (SVOM trigger reference: sb26041103) at 2026-04-11T08:04:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#44262).\n\nWith the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two emission episodes with a T90 of 16.2 +2.1/-1.4 s in the 15-5000 keV band. \n\nThe SVOM/GRM light curve can be found here:\nhttps://www.bursthub.cn//admin/static/svgrb260411B.png\n\nIn addition, the position of this burst, as determined by GOTO (RA= 85.567893 deg, DEC= 1.984983 deg, GCN#44265), is located at about 81 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. \n\nWith this localization, the time-averaged spectrum from T0-2.5 to T0+16.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.81 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 385 +44/-37 keV. The event fluence (10-1000 keV) in this time interval is (2.37 +0.09/-0.09)E-05 erg/cm^2. \n\nThe 1s peak spectrum, measured from T0+6.7 to T0+7.7 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.41 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 331 +20/-17 keV. The flux (10-1000 keV) in this time interval is (6.34 +0.20/-0.20)E-06 erg/cm^2/s.\n\nThe localization of GRB 260411B in the 'Amati' relation diagram is shown at: \nhttps://www.bursthub.cn//admin/static/svgrb260411B_amati.png\nAnd the localization in the 'Yonetoku' relation diagram is shown at: \nhttps://www.bursthub.cn//admin/static/svgrb260411B_yonetoku.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/svgrb260411B_xag_pre.png \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",
  "eventId": "GRB 260411B",
  "submittedHow": "web"
}