{
  "createdOn": 1765405436081,
  "eventId": "GRB 251209A",
  "subject": "GRB 251209A: Fermi GBM observation",
  "submittedHow": "web",
  "submitter": "Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>",
  "bibcode": "2025GCN.43068....1B",
  "body": "E. Bissaldi (Politecnico and INFN Bari) \nreports on behalf of the Fermi GBM Team:\n\n\n\"At 13:24:03.99 UT on 9 December 2025, the Fermi Gamma-Ray Burst Monitor (GBM)\ntriggered and located GRB 251209A (trigger 786979448 / 251209558).\nThe Fermi GBM Final Real-time Localization is reported in GCN 43048.\n\nThe angle from the Fermi LAT boresight at the GBM trigger time is 52 degrees.\n\nThe GBM light curve consists of several structured emission episodes\nwith a duration (T90) of about 57 s (50-300 keV).\nThe time-averaged spectrum from T0-4 s to T0+81 s is\nbest fit by a Band function with Epeak = 105 +/- 4 keV,\nalpha = -1.63 +/- 0.01, and beta = -2.37 +/- 0.06.\n\nThe event fluence (10-1000 keV) in this time interval is\n(6.89 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+49.7 s in the 10-1000 keV band\nis 38.4 +/- 0.6 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/\"",
  "circularId": 43068,
  "format": "text/plain"
}