{
  "bibcode": "2014GCN.15644....1J",
  "body": "P. Jenke (UAH) and S. Xiong (UAH) reports on behalf of the Fermi GBM Team:\n\n\"At 04:45:16.083 UT on December 31 2013, the Fermi Gamma-Ray\nBurst Monitor triggered and located \nGRB 131231A (trigger 410157919/131231198). \nThis GRB was detected in a ground analysis by \nthe Fermi LAT (Sonbas et al. GCN 15640).  \nIt was also detected in optical follow-up observations\nof the GBM position by DARK/NBI (Xu et al. GCN 15641) \nand iPTF (Singer et al. GCN 15643), and confirmed by NOT \nobservations of the Fermi LAT position (Malesani et al. GCN 15642). \nThe on-ground calculated location from GBM is consistent \nwith the positions reported from these follow-up observations.\n\nThe trigger resulted in an Autonomous Repoint Request (ARR) \nthat was accepted and the LAT slewed to the GBM in-flight \nlocation. The initial angle from the LAT boresight is 38 deg\nfrom Fermi/GBM position.  \n\nThe GBM light curve consists of a single large peak preceded \nby a smaller peak which resulted in the trigger.  The \nduration (T90) of the burst was about 31 s (50-300 keV).\nThe time-averaged spectrum from T0+.003 s to T0+56 s is \nbest fit with a Band function  with Epeak = 146 +/- 3 keV, \nalpha = -1.10 +/- 0.01 and beta = -2.14 +/- 0.01.\n\nThe event fluence (10-1000 keV) in this time interval is\n (2.51 +/- 0.01)E-06 erg/cm^2. The 1.0-sec peak photon flux \nmeasured starting from T0+22 s in the 10-1000 keV band\nis 67.3 +/- 0.8 ph/s/cm^2.\n\nThe spectral analysis results presented above are preliminary;\nfinal results will be published in the GBM GRB Catalog.\"",
  "circularId": 15644,
  "createdOn": 1388536968000,
  "email": "peter.a.jenke@nasa.gov",
  "subject": "GRB 131231A: Fermi GBM detection",
  "submitter": "Peter Jenke at MSFC  <peter.a.jenke@nasa.gov>",
  "eventId": "GRB 131231A"
}