{
  "bibcode": "2013GCN.14515....1V",
  "body": "=========================================================================\nF. Verrecchia, C. Pittori (ASDC and INAF/OAR), A. Giuliani (INAF/IASF-Mi),\nM. Marisaldi (INAF/IASF-Bo), F. Longo (University of Trieste and INFN\nTrieste), F. Lucarelli (ASDC and INAF/OAR), E. Del Monte, F. Lazzarotto, I.\nDonnarumma, Y. Evangelista, M. Feroci, L. Pacciani, P. Soffitta, E. Costa,\nI. Lapshov, M. Rapisarda (INAF/IAPS Rome), G. Barbiellini, (INFN Trieste),\nA. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, V.\nFioretti, F. Fuschino, M. Galli (INAF/IASF-Bo), A. Chen, S. Mereghetti,\nF. Perotti, P. Caraveo (INAF/IASF-Mi), M. Cardillo, E. Striani, M. Tavani\n(INAF/IAPS Rome, and Univ. Roma Tor Vergata), A. Argan, G. Piano, S.\nSabatini, V. Vittorini (INAF/IAPS Rome), G. Pucella (ENEA Frascati), A.\nPellizzoni, A. Trois (INAF/OA Cagliari), M. Pilia (ASTRON), S. Vercellone\n(INAF/IASF-Pa), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Morselli, P.\nPicozza (INFN Roma-2), M. Prest, E. Vallazza (Universita` \ndell'Insubria), P.\nLipari, D. Zanello (INFN Roma-1), P. Giommi (ASI), and G. Valentini (ASI),\non behalf of the AGILE Team, report:\n\nThe AGILE Gamma Ray Imaging Detector (GRID) detected high energy emission\nfrom GRB 130427A (A. Maselli et al., GCN 14448), also reported\nby Fermi-LAT (S. Zhu et al., GCN 14471).\nA preliminary analysis of the AGILE-GRID data in temporal coincidence with\nthe GRB shows a significant excess of gamma-ray photons above 50 MeV at the\nlocation of the event. The emission detected by the AGILE-GRID mostly\noccurred between ~ t0 + 180 sec and t0 + 700 sec where t0 is 27 April 2013\nat 07:47:15 UT. During this interval, the burst position was inside the\ninstrument FOV.\n\nA maximum likelihood analysis of the AGILE-GRID data integrating over 12\nhours, from 2013-04-27 05:00 UT to 2013-04-27 17:00 UT, using the standard\nparameters used by AGILE quick look to detect persistent gamma-ray sources,\nyields a detection at a significance level larger than 6 sigma, and a mean\nflux F = (8.0+/-2.7) 10-6 ph/cm2/s (E > 100 MeV).\nThe preliminary photon spectral index obtained with this integration is\n1.55 +/- 0.30.\nDue to the exceptionally high fluence above 100 MeV of this burst, it is\npossible for the first time to derive its properties using the maximum\nlikelihood techniques routinely used in the standard data analysis of\nAGILE-GRID point sources.\n\nThe GRB also triggered the AGILE Minicalorimeter (MCAL), sensitive to\ngamma-rays above 350 keV, at the time 07:47:06 UT.\nAccording to the MCAL light curve, the emission lasts for about 20 s \ndivided\ninto three main episodes. Although the large initial off-axis angle (more\nthan 120 degrees) prevents an accurate spectral analysis of MCAL data,\nsignificant emission above 15 MeV is detected.\n\nThis measurement was obtained with AGILE observing a large portion of the\nsky in spinning mode.\n\nThis message may be cited.\n=========================================================================",
  "circularId": 14515,
  "createdOn": 1367337444000,
  "email": "francesco.verrecchia@asdc.asi.it",
  "subject": "GRB 130427A: high energy gamma-ray detection by AGILE",
  "submitter": "Francesco Verrecchia at ASDC  <francesco.verrecchia@asdc.asi.it>",
  "eventId": "GRB 130427A"
}