{
  "eventId": "GRB 240421B",
  "subject": "GRB 240421B: Fermi GBM Observation",
  "body": "C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 09:42:41.91 UT on 21 April 2024, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 240421B (trigger 735385366/240421405).\nwhich was also detected by Swift BAT (M. A. Williams et al. 2024, GCN 36208).\nThe Fermi GBM on-ground location is consistent with the Swift BAT position.\n\nThe angle from the Fermi LAT boresight is 29 degrees.\n\nThe GBM light curve consists of multiple peaks with a duration (T90)\nof about 12.3 s (50-300 keV). The time-averaged spectrum\nfrom T0+0.003 to T0+18.4 s is best fit by\na Band function with Epeak = 141 +/- 8 keV,\nalpha = -0.91 +/- 0.04, and beta = -2.31 +/- 0.09.\n\nThe event fluence (10-1000 keV) in this time interval is\n(1.28 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+12 s in the 10-1000 keV band is 31.9 +/- 0.5 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/\"",
  "createdOn": 1713740742176,
  "submittedHow": "web",
  "bibcode": "2024GCN.36218....1F",
  "submitter": "Cori Fletcher at USRA <cfletcher@usra.edu>",
  "circularId": 36218
}