{
  "createdOn": 1746432047937,
  "bibcode": "2025GCN.40346....1B",
  "eventId": "GRB 250504A",
  "format": "text/plain",
  "body": "S. Bala (USRA) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\n\"At 23:25:54.78 UT on 04 May 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 250504A (trigger 768093959/250504976),\nwhich was also detected by Swift BAT (M. J. Moss et al. 2025, GCN 40343).\nThe Fermi GBM on-ground location is consistent with the Swift BAT position.\n\nThe angle from the Fermi LAT boresight is 111 degrees.\n\nThe GBM light curve consists of multiple peaks with a duration (T90)\nof about 49 s (50-300 keV). The time-averaged spectrum\nfrom T0+0.003 to T0+59.393 s is best fit by\na power law function with an exponential high-energy cutoff.\nThe power law index is -1.06 +/- 0.08 and the cutoff energy,\nparameterized as Epeak, is 621 +/- 130 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(1.20 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+10 s in the 10-1000 keV band is 3.6 +/- 0.3 ph/s/cm^2.\n\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/\"",
  "subject": "GRB 250504A: Fermi GBM Observation",
  "circularId": 40346,
  "submittedHow": "web",
  "submitter": "Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>"
}