{
  "format": "text/plain",
  "bibcode": "2025GCN.39724....1S",
  "subject": "GRB 250312B: Fermi GBM Observation",
  "submittedHow": "web",
  "circularId": 39724,
  "createdOn": 1742000202696,
  "submitter": "Lorenzo Scotton at UAH <lscottongcn@outlook.com>",
  "body": "L. Scotton (UAH) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 20:36:56.64 UT on 12 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 250312B (trigger 763504621/250312859),\nwhich was also localized by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 39708).\nThe Fermi GBM on-ground location was given in GCN 39692 and it is consistent \nwith the Swift/BAT-GUANO localization skymap.\n\nThe angle from the Fermi LAT boresight is 105 degrees.\n\nThe GBM light curve consists of single emission with two over lapping pulses, \nwith a duration (T90) of about 5.4 s (50-300 keV). The time-averaged spectrum \nfrom T0-1.0 to T0+5.5 s is best fit by a power law function with an exponential \nhigh-energy cutoff. The power law index is -1.1 +/- 0.1 and the cutoff energy,\nparameterized as Epeak, is 260 +/- 50 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(2.7 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+0.003 s in the 10-1000 keV band is 4.4 +/- 0.3 ph/s/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/\"",
  "eventId": "GRB 250312B"
}