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Detection of a Spectral Break in the Extra Hard Component of GRB 090926A

Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, Magnus LU ; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D. and Bechtol, K., et al. (2011) In Astrophysical Journal 729(2).
Abstract
We report on the observation of the bright, long gamma-ray burst, GRB 090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in the light curve that is present in all detectors that see the burst, and this in turn suggests that there is a common region of emission across the entire Fermi energy range. In addition, while a separate high-energy power-law component has already been observed in other gamma-ray bursts, here we report for the first time the detection with good significance of a high-energy spectral break (or cutoff) in this power-law component... (More)
We report on the observation of the bright, long gamma-ray burst, GRB 090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in the light curve that is present in all detectors that see the burst, and this in turn suggests that there is a common region of emission across the entire Fermi energy range. In addition, while a separate high-energy power-law component has already been observed in other gamma-ray bursts, here we report for the first time the detection with good significance of a high-energy spectral break (or cutoff) in this power-law component around 1.4 GeV in the time-integrated spectrum. If the spectral break is caused by opacity to electron-positron pair production within the source, then this observation allows us to compute the bulk Lorentz factor for the outflow, rather than a lower limit. (Less)
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gamma-ray burst: individual (GRB 090926A)
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Astrophysical Journal
volume
729
issue
2
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University of Chicago Press
external identifiers
  • wos:000288608700037
  • scopus:79952159931
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0004-637X
DOI
10.1088/0004-637X/729/2/114
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English
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70bc9c14-7e88-444d-b024-4e4816e48e36 (old id 1926177)
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2011-05-10 14:05:49
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@article{70bc9c14-7e88-444d-b024-4e4816e48e36,
  abstract     = {We report on the observation of the bright, long gamma-ray burst, GRB 090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in the light curve that is present in all detectors that see the burst, and this in turn suggests that there is a common region of emission across the entire Fermi energy range. In addition, while a separate high-energy power-law component has already been observed in other gamma-ray bursts, here we report for the first time the detection with good significance of a high-energy spectral break (or cutoff) in this power-law component around 1.4 GeV in the time-integrated spectrum. If the spectral break is caused by opacity to electron-positron pair production within the source, then this observation allows us to compute the bulk Lorentz factor for the outflow, rather than a lower limit.},
  author       = {Ackermann, M. and Ajello, M. and Asano, K. and Axelsson, Magnus and Baldini, L. and Ballet, J. and Barbiellini, G. and Baring, M. G. and Bastieri, D. and Bechtol, K. and Bellazzini, R. and Berenji, B. and Bhat, P. N. and Bissaldi, E. and Blandford, R. D. and Bonamente, E. and Borgland, A. W. and Bouvier, A. and Bregeon, J. and Brez, A. and Briggs, M. S. and Brigida, M. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G. A. and Cameron, R. A. and Caraveo, P. A. and Carrigan, S. and Casandjian, J. M. and Cecchi, C. and Celik, O. and Chaplin, V. and Charles, E. and Chekhtman, A. and Chiang, J. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Connaughton, V. and Conrad, J. and Cutini, S. and Dermer, C. D. and De Angelis, A. and De Palma, F. and Dingus, B. L. and Silva, E. Do Couto E. and Drell, P. S. and Dubois, R. and Favuzzi, C. and Fegan, S. J. and Ferrara, E. C. and Focke, W. B. and Frailis, M. and Fukazawa, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Germani, S. and Giglietto, N. and Giordano, F. and Giroletti, M. and Glanzman, T. and Godfrey, G. and Goldstein, A. and Granot, J. and Greiner, J. and Grenier, I. A. and Grove, J. E. and Guiriec, S. and Hadasch, D. and Hanabata, Y. and Harding, A. K. and Hayashi, K. and Hayashida, M. and Hays, E. and Horan, D. and Hughes, R. E. and Itoh, R. and Johannesson, G. and Johnson, A. S. and Johnson, W. N. and Kamae, T. and Katagiri, H. and Kataoka, J. and Kippen, R. M. and Knoedlseder, J. and Kocevski, D. and Kouveliotou, C. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S. -H. and Garde, M. Llena and Longo, F. and Loparco, F. and Lovellette, M. N. and Lubrano, P. and Makeev, A. and Mazziotta, M. N. and McBreen, S. and McEnery, J. E. and McGlynn, S. and Meegan, C. and Mehault, J. and Meszaros, P. and Michelson, P. F. and Mizuno, T. and Monte, C. and Monzani, M. E. and Moretti, E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Nakajima, H. and Nakamori, T. and Naumann-Godo, M. and Nishino, S. and Nolan, P. L. and Norris, J. P. and Nuss, E. and Ohno, M. and Ohsugi, T. and Okumura, A. and Omodei, N. and Orlando, E. and Ormes, J. F. and Ozaki, M. and Paciesas, W. S. and Paneque, D. and Panetta, J. H. and Parent, D. and Pelassa, V. and Pepe, M. and Pesce-Rollins, M. and Petrosian, V. and Piron, F. and Porter, T. A. and Preece, R. and Racusin, J. L. and Raino, S. and Rando, R. and Rau, A. and Razzano, M. and Razzaque, S. and Reimer, A. and Reimer, O. and Reposeur, T. and Reyes, L. C. and Ripken, J. and Ritz, S. and Roth, M. and Ryde, F. and Sadrozinski, H. F. -W. and Sander, A. and Scargle, J. D. and Strickman, M. S. and Suson, D. J. and Tajima, H. and Takahashi, H. and Tanaka, T. and Tanaka, Y. and Thayer, J. B. and Thayer, J. G. and Tibaldo, L. and Tierney, D. and Toma, K. and Torres, D. F. and Tosti, G. and Tramacere, A. and Uchiyama, Y. and Uehara, T. and Usher, T. L. and Vandenbroucke, J. and van der Horst, A. J. and Vasileiou, V. and Vilchez, N. and Vitale, V. and von Kienlin, A. and Waite, A. P. and Wang, P. and Wilson-Hodge, C. and Winer, B. L. and Wood, K. S. and Wu, X. F. and Yamazaki, R. and Yang, Z. and Ylinen, T. and Ziegler, M.},
  issn         = {0004-637X},
  keyword      = {gamma-ray burst: individual (GRB 090926A)},
  language     = {eng},
  number       = {2},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {Detection of a Spectral Break in the Extra Hard Component of GRB 090926A},
  url          = {http://dx.doi.org/10.1088/0004-637X/729/2/114},
  volume       = {729},
  year         = {2011},
}