{
  "eventId": "GRB 250919A",
  "submitter": "oindabimukherjee@gmail.com",
  "format": "text/plain",
  "createdOn": 1758308173391,
  "subject": "GRB 250919A: Fermi GBM Observation",
  "circularId": 41890,
  "bibcode": "2025GCN.41890....1M",
  "body": "O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 00:28:52.28 UT on 19 September 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 250919A (trigger 779934537/250919020)\nwhich was also detected by Fermi-LAT ( A. Holzmann Airasca et al. 2025, GCN 41884), \nSVOM-GRM (Chen-Wei Wang et al. 2025, GCN 41882), \nSwift-XRT (J.P. Osborne et al., 2025, GCN 41885), \nEP-WXT (Y.F. Liang et al. 2025, GCN 41879), \nSwift-UVOT (S.R. Oates et al. 2025, GCN 41886),\nGemini/GMOS-S spectroscopic redshift z = 1.145 (A. J. Levan et al. 2025, GCN 41883) \nThe Fermi GBM on-ground location is consistent with the position measured by other instruments.\n\nThe angle from the Fermi LAT boresight is 56 degrees.\n\nThe GBM light curve consists of a very bright emission episode, \nfollowed by a fainter second emission episode, with a total duration (T90)\nof about 129.3 s (50-300 keV). The time-averaged spectrum\nfrom T0+3 to T0+190 s is best fit by\na Band function with Epeak = 476 +/- 6 keV,\nalpha = -0.88 +/- 0.01, and beta = -2.39 +/- 0.04.\n\nThe event fluence (10-1000 keV) in this time interval is\n(4.36 +/- 0.002)E-04 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+33 s in the 10-1000 keV band is 115.2 +/- 0.7 ph/s/cm^2.\n\nThe time-averaged spectrum of the main pulse\nfrom T0+3 to T0+58 s is best fit by\na Band function with Epeak = 475 +/- 5 keV,\nalpha = -0.7 +/- 0.01, and beta = -2.38 +/- 0.03.\nThe event fluence (10-1000 keV) in this time interval is\n(2.56 +/- 0.01)E-04 erg/cm^2.\n\nThe time-averaged spectrum of the second pulse\nfrom T0+111 to T0+190 s is best fit by\na Band function with Epeak = 220 +/- 12 keV,\nalpha = -1.12 +/- 0.02, and beta = -1.93 +/- 0.03.\nThe event fluence (10-1000 keV) in this time interval is\n(5.77 +/- 0.05)E-05 erg/cm^2.\n\nThe spectral analysis results presented above are preliminary;\nfinal results will be published in the GBM GRB Catalog:\nhttps://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html\n\nFor Fermi GBM data and info, please visit the official Fermi GBM Support Page:\nhttps://fermi.gsfc.nasa.gov/ssc/data/access/gbm/\"",
  "submittedHow": "web"
}