{
  "circularId": 38507,
  "submitter": "Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>",
  "createdOn": 1733784655484,
  "submittedHow": "web",
  "eventId": "GRB 241209D",
  "format": "text/plain",
  "subject": "GRB 241209D: Fermi GBM Observation",
  "bibcode": "2024GCN.38507....1M",
  "body": "C. Malacaria (INAF-OAR) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 10:59:44.09 UT on 09 December 2024, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 241209D (trigger 755434789/241209458).\nwhich was also detected by Swift BAT (T. M. Parsotan et al. 2024, GCN 38489, \nM.R. Goad et al. 2024, GCN 38491).\nThe Fermi GBM on-ground location is consistent with the Swift BAT position.\n\nThe angle from the Fermi LAT boresight is 82 degrees.\n\nThe GBM light curve consists of a single emission episode with a duration (T90)\nof about 45 s (50-300 keV). The time-averaged spectrum\nfrom T0-0.8 to T0+44.3 s is best fit by\na power law function with an exponential high-energy cutoff.\nThe power law index is -0.40 +/- 0.07 and the cutoff energy,\nparameterized as Epeak, is 110 +/- 3 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(9.5 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+5.9 s in the 10-1000 keV band is 4.4 +/- 0.3 ph/s/cm^2.\n\nA Band function fits the spectrum equally well\nwith Epeak= 107 +/- 4 keV, alpha = -0.35 +/- 0.08 and beta = -3.4 +/- 0.6.\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/\""
}