{
  "bibcode": "2021GCN.30225....1M",
  "body": "J. Mangan (UCD), R. Dunwoody (UCD), C. Meegan (UAH)\nreport on behalf of the Fermi GBM Team:\n\nAt 10:54:44.812 UT on 21 Apr 2021, the Fermi Gamma-Ray Burst Monitor (GBM)\ntriggered and located GRB 210421B (trigger 640695289 / 210421455)\nwhich was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2021, GCN\n29877)\nThe Fermi GBM Final Real-time Localization (GCN 29870) is consistent with\nthe Swift position.\n\nThe angle from the Fermi LAT boresight at the GBM trigger time is 20.1\ndegrees.\n\nThe GBM light curve consists of a single peak\nwith a duration (T90) of about 11 s (50-300 keV).\nThe time-averaged spectrum from T0-1.536 s to T0+9.728 is\nbest fit by a power law function with an exponential\nhigh-energy cutoff.  The power law index is -0.98 +/- 0.11 and\nthe cutoff energy, parameterized as Epeak, is 1253.00 +/- 500.00 keV\n\nThe event fluence (10-1000 keV) in this time interval is\n(3.655 +/- 0.225)E-06 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0-0.384 s in the 10-1000 keV band\nis 2.74 +/- 0.26 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\nPage:\nhttps://fermi.gsfc.nasa.gov/ssc/data/access/gbm/",
  "circularId": 30225,
  "createdOn": 1623520520000,
  "email": "joseph.mangan@ucdconnect.ie",
  "subject": "GRB 210421B: Fermi GBM detection",
  "submitter": "Joe Mangan at UCD  <joseph.mangan@ucdconnect.ie>",
  "eventId": "GRB 210421B"
}