{
  "bibcode": "2011GCN.12100....1G",
  "body": "David Gruber (MPE), Nicola Omodei (Stanford U.), Vandiver Chaplin (UAH), \nJ. Chiang (KIPAC/SLAC), J. McEnery (NASA/GSFC), J. L. Racusin (NASA/GSFC) \nreport on behalf of the Fermi GBM and LAT Teams: \n\nAt 21:08:18.24 UT on 25 June 2011, the Fermi Gamma-Ray Burst Monitor \ntriggered and located GRB 110625A (trigger 330728900 / 110625881), which \nwas also detected by the Swift/BAT (Page et al. 2011, GCN 12088). The GBM \non-ground location is consistent with the Swift position.\n\nThe angle from the Fermi LAT boresight is 88 degrees at the trigger time. \nMoreover, this burst was bright enough to result in a Fermi spacecraft \nautonomous rapid repoint (ARR) maneuver.\n\nThis burst was also independently detected by INTEGRAL SPI-ACS.\n\nThe GBM light curve shows several pulses with a duration (T90) of about \n27.7 +/- 1.4 s (50-300 keV). The time-averaged spectrum from T0-2.048 s \nto T0+60.417 s is best fit by a power law function with an exponential \nhigh-energy cutoff.  The power law index is -0.95 +/- 0.01 and the cutoff \nenergy, parameterized as Epeak, is 209 +/- 3 keV.\n\nThe event fluence (10-1000 keV) in this time interval is \n(6.71 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting \nfrom T0+23.9 s in the 10-1000 keV band is 77.3 +/- 0.7 ph/s/cm^2.\n\nA Band function fits the spectrum equally well with Epeak= 175 +/- 5 keV, \nalpha = -0.85 +/- 0.02 and beta = -2.37 +/- 0.05. \n\nThe spectral analysis results presented above are preliminary; \nfinal results will be published in the GBM GRB Catalog.\n\nThe ARR maneuver put the GRB inside the Fermi/LAT field of view \nfor several hundred seconds (from ~100-600 seconds after the GBM trigger).\n\nThe Spacecraft continued its maneuver toward the Fermi GBM flight software \nreconstructed position, that was off by 68 degrees from the Enhanced Swift/XRT \nposition (GCN 12092), providing non-optimal exposure for LAT follow-up \nobservations.\n\nWe analyzed the LAT data and we see significant high-energy emission from a \npoint source coincident with the XRT position, confirming the already \nreported results by P.H.T. Tam and A.K.H. Kong (GCN 12097). \n\nWe model the source spectrum with a power law model N(e) = N0 e^{\\beta}, and \nthe background including both the contribution from the Galactic diffuse \nemission and the isotropic contribution due to the residual contamination of \ncharged particles.\n\nWe detect the GRB in two distinct time periods. In the first time bin (from \n237.1 seconds to 316.2 seconds after the GBM trigger), we measure a flux \n(100 MeV-10 GeV) of (4.9 +/- 1.9) x 1e-05 ph/cm^2/s and a spectral index beta \nof -2.1 +/- 0.3, with a Test Statistic TS=31.\n\nIn the second time bin, from 421.7 to 562.3 seconds after the GBM trigger, \nthe measured flux is (3.7 +/- 1.5) x 1e-5  ph/cm^2/s with spectral index beta \nof -3.6 +/- 0.8 and a TS=19 (stat errors only).\n\nThe Fermi LAT point of contact for this burst is Nicola Omodei (nicola.omodei@gmail.com).\n\nThe Fermi LAT is a pair conversion telescope designed to cover the energy band \nfrom 20 MeV to greater than 300 GeV. It is the product of an international \ncollaboration between NASA and DOE in the U.S. and many scientific institutions \nacross France, Italy, Japan and Sweden.",
  "circularId": 12100,
  "createdOn": 1309209891000,
  "email": "dgruber@mpe.mpg.de",
  "subject": "GRB 110625A: Fermi GBM and LAT observations",
  "submitter": "David Gruber at MPE  <dgruber@mpe.mpg.de>",
  "eventId": "GRB 110625A"
}