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GRB110721A: An extreme peak energy and signatures of the photosphere

  • M. Axelsson
  • , L. Baldini
  • , G. Barbiellini
  • , M. G. Baring
  • , R. Bellazzini
  • , J. Bregeon
  • , M. Brigida
  • , P. Bruel
  • , R. Buehler
  • , G. A. Caliandro
  • , R. A. Cameron
  • , P. A. Caraveo
  • , C. Cecchi
  • , R. C.G. Chaves
  • , A. Chekhtman
  • , J. Chiang
  • , R. Claus
  • , J. Conrad
  • , S. Cutini
  • , F. D'Ammando
  • F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, Y. Fukazawa, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, M. Giroletti, G. Godfrey, S. Guiriec, D. Hadasch, Y. Hanabata, M. Hayashida, X. Hou, S. Iyyani, M. S. Jackson, D. Kocevski, M. Kuss, J. Larsson, S. Larsson, F. Longo, F. Loparco, C. Lundman, M. N. Mazziotta, J. E. McEnery, T. Mizuno, M. E. Monzani, E. Moretti, A. Morselli, S. Murgia, E. Nuss, T. Nymark, M. Ohno, N. Omodei, M. Pesce-Rollins, F. Piron, G. Pivato, J. L. Racusin, S. Rainò, M. Razzano, S. Razzaque, A. Reimer, M. Roth, F. Ryde, D. A. Sanchez, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, M. Stamatikos, L. Tibaldo, M. Tinivella, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, B. L. Winer, K. S. Wood, J. M. Burgess, P. N. Bhat, E. Bissaldi, M. S. Briggs, V. Connaughton, G. Fishman, G. Fitzpatrick, S. Foley, D. Gruber, R. M. Kippen, C. Kouveliotou, P. Jenke, S. McBreen, S. McGlynn, C. Meegan, W. S. Paciesas, V. Pelassa, R. Preece, D. Tierney, A. Von Kienlin, C. Wilson-Hodge, S. Xiong, A. Pe'Er
  • KTH Royal Institute of Technology
  • Stockholm University
  • Oskar Klein Centre
  • National Institute for Nuclear Physics
  • University of Trieste
  • Rice University
  • Polytechnic University of Bari
  • École polytechnique
  • Stanford University
  • CSIC
  • Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna
  • University of Perugia
  • CEA-IRFU/CNRS/Université Paris Diderot
  • George Mason University
  • Italian Space Agency
  • National Institute for Astrophysics
  • Naval Research Laboratory
  • NASA Goddard Space Flight Center
  • Hiroshima University
  • Kyoto University
  • Centre d'Etudes Nucléaires Bordeaux-Gradingnan (CENBG)
  • University of Maryland
  • Université Montpellier 2
  • JAXA Institute of Space and Astronautical Science
  • University of Padua
  • University of California at Santa Cruz
  • Innsbruck Medical University
  • University of Washington
  • Max Planck Institute for Nuclear Physics
  • NYCB Real-Time Computing Inc.
  • Ohio State University
  • Consorzio Interuniversitario per la Fisica Spaziale (CIFS)
  • University of Rome Tor Vergata
  • University of Alabama in Huntsville
  • NASA Marshall Space Flight Center
  • University College Dublin
  • Max Planck Institute for Extraterrestrial Physics
  • Los Alamos National Laboratory
  • Technical University of Munich
  • Universities Space Research Association
  • Harvard & Smithsonian

Research output: Contribution to journalArticlepeer-review

171 Citations (Scopus)

Abstract

GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for 24.5s (in the GBM) and had a peak flux of (5.7 ± 0.2) × 10 -5ergs-1cm-2. The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 ± 2MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89 ± 0.10. The temperature of the blackbody component also decreased, starting from 80keV, and the decay showed a significant break after 2s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.

Original languageEnglish
Article numberL31
JournalAstrophysical Journal Letters
Volume757
Issue number2
DOIs
Publication statusPublished - 1 Oct 2012
Externally publishedYes

Keywords

  • gamma-ray burst: general
  • gamma-ray burst: individual (GRB110721A)
  • radiation mechanisms: thermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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