160 articles – 2213 references  [version française]
HAL: in2p3-00743070, version 1

Detailed view  Export this paper
Astrophysical Journal Letters 757 (2012) L31
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. Bruel1, R. Buehler, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, C. Cecchi, R.C.G. Chaves2, 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. Fegan1, 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. Hou3, 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. Nuss4, T. Nymark, M. Ohno, N. Omodei, M. Pesce-Rollins, F. Piron4, G. Pivato, J. L. Racusin, S. Rain'o, M. Razzano, S. Razzaque, A. Reimer, M. Roth, F. Ryde, D.A. Sanchez, C. Sgr'o, E. J. Siskind, G. Spandre, P. Spinelli, M. Stamatikos, L. Tibaldo, M. Tinivella, T. L. Usher, J. Vandenbroucke, V. Vasileiou4, 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. Pacisas, V. Pelassa4, R. Preece, D. Tierney, A. von Kienlin, C. Wilson-Hodge, S. Xiong, A. Pe'er

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 ~24.5 seconds (in the GBM) and had a peak flux of 5.7\pm0.2 x 10^{-5} erg/s/cm^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\pm2 MeV, 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--100 MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89\pm0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 seconds. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.
1:  LLR - Laboratoire Leprince-Ringuet
2:  Max-Planck-Institut für Kernphysik
3:  CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
4:  LUPM - Laboratoire Univers et Particules de Montpellier
Physics/Astrophysics/High Energy Astrophysical Phenomena

Sciences of the Universe/Astrophysics/High Energy Astrophysical Phenomena