Detection of a spectral break in the extra hard component of GRB 090926A

M. Ackermann, M. Ajello, K. Asano, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, M. G. Baring, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, P. N. Bhat, E. Bissaldi, R. D. Blandford, E. Bonamente, A. W. Borgland, A. Bouvier, J. Bregeon, A. Brez & 179 others M. S. Briggs, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, S. Carrigan, J. M. Casandjian, C. Cecchi, Ö Çelik, V. Chaplin, E. Charles, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, V. Connaughton, J. Conrad, S. Cutini, C. D. Dermer, A. De Angelis, F. De Palma, B. L. Dingus, E. Do Couto E Silva, P. S. Drell, R. Dubois, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, M. Frailis, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, A. Goldstein, J. Granot, J. Greiner, I. A. Grenier, J. E. Grove, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, K. Hayashi, M. Hayashida, E. Hays, D. Horan, R. E. Hughes, R. Itoh, G. Jóhannesson, A. S. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, Jun Kataoka, R. M. Kippen, J. Knödlseder, D. Kocevski, C. Kouveliotou, M. Kuss, J. Lande, L. Latronico, S. H. Lee, M. Llena Garde, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, A. Makeev, M. N. Mazziotta, S. McBreen, J. E. McEnery, S. McGlynn, C. Meegan, J. Mehault, P. Mészáros, P. F. Michelson, T. Mizuno, C. Monte, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, S. Murgia, H. Nakajima, T. Nakamori, M. Naumann-Godo, S. Nishino, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, W. S. Paciesas, D. Paneque, J. H. Panetta, D. Parent, V. Pelassa, M. Pepe, M. Pesce-Rollins, V. Petrosian, F. Piron, T. A. Porter, R. Preece, J. L. Racusin, S. Rainò, R. Rando, A. Rau, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, L. C. Reyes, J. Ripken, S. Ritz, M. Roth, F. Ryde, H. F W Sadrozinski, A. Sander, J. D. Scargle, T. L. Schalk, C. Sgrò, E. J. Siskind, P. D. Smith, G. Spandre, P. Spinelli, M. Stamatikos, F. W. Stecker, M. S. Strickman, D. J. Suson, H. Tajima, H. Takahashi, T. Tanaka, Y. Tanaka, J. B. Thayer, J. G. Thayer, L. Tibaldo, D. Tierney, K. Toma, D. F. Torres, G. Tosti, A. Tramacere, Y. Uchiyama, T. Uehara, T. L. Usher, J. Vandenbroucke, A. J. Van Der Horst, V. Vasileiou, N. Vilchez, V. Vitale, A. Von Kienlin, A. P. Waite, P. Wang, C. Wilson-Hodge, B. L. Winer, K. S. Wood, X. F. Wu, R. Yamazaki, Z. Yang, T. Ylinen, M. Ziegler

    Research output: Contribution to journalArticle

    152 Citations (Scopus)

    Abstract

    We report on the observation of the bright, long gamma-ray burst, GRB090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB090926A 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.

    Original languageEnglish
    Article number114
    JournalAstrophysical Journal
    Volume729
    Issue number2
    DOIs
    Publication statusPublished - 2011 Mar 10

    Fingerprint

    gamma ray bursts
    bursts
    power law
    telescopes
    energy
    Fermi Gamma-ray Space Telescope
    electron-positron pairs
    pair production
    opacity
    spikes
    light curve
    monitors
    outflow
    cut-off
    electron
    detectors
    detection

    Keywords

    • gamma-ray burst: individual (GRB 090926A)

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Ackermann, M., Ajello, M., Asano, K., Axelsson, M., Baldini, L., Ballet, J., ... Ziegler, M. (2011). Detection of a spectral break in the extra hard component of GRB 090926A. Astrophysical Journal, 729(2), [114]. https://doi.org/10.1088/0004-637X/729/2/114

    Detection of a spectral break in the extra hard component of GRB 090926A. / Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö; Chaplin, V.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; De Angelis, A.; De Palma, F.; Dingus, B. L.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Goldstein, A.; Granot, J.; Greiner, J.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashi, K.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Kippen, R. M.; Knödlseder, J.; Kocevski, D.; Kouveliotou, C.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S. H.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakajima, H.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T. A.; Preece, R.; Racusin, J. L.; Rainò, S.; Rando, R.; Rau, A.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Reyes, L. C.; Ripken, J.; Ritz, S.; Roth, M.; Ryde, F.; Sadrozinski, H. F W; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stecker, F. W.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Tanaka, Y.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Tierney, D.; Toma, K.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; Van Der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Wu, X. F.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.

    In: Astrophysical Journal, Vol. 729, No. 2, 114, 10.03.2011.

    Research output: Contribution to journalArticle

    Ackermann, M, Ajello, M, Asano, K, Axelsson, M, Baldini, L, Ballet, J, Barbiellini, G, Baring, MG, Bastieri, D, Bechtol, K, Bellazzini, R, Berenji, B, Bhat, PN, Bissaldi, E, Blandford, RD, Bonamente, E, Borgland, AW, Bouvier, A, Bregeon, J, Brez, A, Briggs, MS, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Carrigan, S, Casandjian, JM, Cecchi, C, Çelik, Ö, Chaplin, V, Charles, E, Chekhtman, A, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Connaughton, V, Conrad, J, Cutini, S, Dermer, CD, De Angelis, A, De Palma, F, Dingus, BL, Do Couto E Silva, E, Drell, PS, Dubois, R, Favuzzi, C, Fegan, SJ, Ferrara, EC, Focke, WB, Frailis, M, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Gehrels, N, Germani, S, Giglietto, N, Giordano, F, Giroletti, M, Glanzman, T, Godfrey, G, Goldstein, A, Granot, J, Greiner, J, Grenier, IA, Grove, JE, Guiriec, S, Hadasch, D, Hanabata, Y, Harding, AK, Hayashi, K, Hayashida, M, Hays, E, Horan, D, Hughes, RE, Itoh, R, Jóhannesson, G, Johnson, AS, Johnson, WN, Kamae, T, Katagiri, H, Kataoka, J, Kippen, RM, Knödlseder, J, Kocevski, D, Kouveliotou, C, Kuss, M, Lande, J, Latronico, L, Lee, SH, Llena Garde, M, Longo, F, Loparco, F, Lovellette, MN, Lubrano, P, Makeev, A, Mazziotta, MN, McBreen, S, McEnery, JE, McGlynn, S, Meegan, C, Mehault, J, Mészáros, P, Michelson, PF, Mizuno, T, Monte, C, Monzani, ME, Moretti, E, Morselli, A, Moskalenko, IV, Murgia, S, Nakajima, H, Nakamori, T, Naumann-Godo, M, Nishino, S, Nolan, PL, Norris, JP, Nuss, E, Ohno, M, Ohsugi, T, Okumura, A, Omodei, N, Orlando, E, Ormes, JF, Ozaki, M, Paciesas, WS, Paneque, D, Panetta, JH, Parent, D, Pelassa, V, Pepe, M, Pesce-Rollins, M, Petrosian, V, Piron, F, Porter, TA, Preece, R, Racusin, JL, Rainò, S, Rando, R, Rau, A, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reposeur, T, Reyes, LC, Ripken, J, Ritz, S, Roth, M, Ryde, F, Sadrozinski, HFW, Sander, A, Scargle, JD, Schalk, TL, Sgrò, C, Siskind, EJ, Smith, PD, Spandre, G, Spinelli, P, Stamatikos, M, Stecker, FW, Strickman, MS, Suson, DJ, Tajima, H, Takahashi, H, Tanaka, T, Tanaka, Y, Thayer, JB, Thayer, JG, Tibaldo, L, Tierney, D, Toma, K, Torres, DF, Tosti, G, Tramacere, A, Uchiyama, Y, Uehara, T, Usher, TL, Vandenbroucke, J, Van Der Horst, AJ, Vasileiou, V, Vilchez, N, Vitale, V, Von Kienlin, A, Waite, AP, Wang, P, Wilson-Hodge, C, Winer, BL, Wood, KS, Wu, XF, Yamazaki, R, Yang, Z, Ylinen, T & Ziegler, M 2011, 'Detection of a spectral break in the extra hard component of GRB 090926A', Astrophysical Journal, vol. 729, no. 2, 114. https://doi.org/10.1088/0004-637X/729/2/114
    Ackermann M, Ajello M, Asano K, Axelsson M, Baldini L, Ballet J et al. Detection of a spectral break in the extra hard component of GRB 090926A. Astrophysical Journal. 2011 Mar 10;729(2). 114. https://doi.org/10.1088/0004-637X/729/2/114
    Ackermann, M. ; Ajello, M. ; Asano, K. ; Axelsson, M. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Baring, M. G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Berenji, B. ; Bhat, P. N. ; Bissaldi, E. ; Blandford, R. D. ; Bonamente, E. ; Borgland, A. W. ; Bouvier, A. ; Bregeon, J. ; Brez, A. ; Briggs, M. S. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Carrigan, S. ; Casandjian, J. M. ; Cecchi, C. ; Çelik, Ö ; Chaplin, V. ; Charles, E. ; Chekhtman, A. ; Chiang, J. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Connaughton, V. ; Conrad, J. ; Cutini, S. ; Dermer, C. D. ; De Angelis, A. ; De Palma, F. ; Dingus, B. L. ; Do Couto E Silva, E. ; Drell, P. S. ; Dubois, R. ; Favuzzi, C. ; Fegan, S. J. ; Ferrara, E. C. ; Focke, W. B. ; Frailis, M. ; Fukazawa, Y. ; Funk, S. ; Fusco, P. ; Gargano, F. ; Gasparrini, D. ; Gehrels, N. ; Germani, S. ; Giglietto, N. ; Giordano, F. ; Giroletti, M. ; Glanzman, T. ; Godfrey, G. ; Goldstein, A. ; Granot, J. ; Greiner, J. ; Grenier, I. A. ; Grove, J. E. ; Guiriec, S. ; Hadasch, D. ; Hanabata, Y. ; Harding, A. K. ; Hayashi, K. ; Hayashida, M. ; Hays, E. ; Horan, D. ; Hughes, R. E. ; Itoh, R. ; Jóhannesson, G. ; Johnson, A. S. ; Johnson, W. N. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Kippen, R. M. ; Knödlseder, J. ; Kocevski, D. ; Kouveliotou, C. ; Kuss, M. ; Lande, J. ; Latronico, L. ; Lee, S. H. ; Llena Garde, M. ; Longo, F. ; Loparco, F. ; Lovellette, M. N. ; Lubrano, P. ; Makeev, A. ; Mazziotta, M. N. ; McBreen, S. ; McEnery, J. E. ; McGlynn, S. ; Meegan, C. ; Mehault, J. ; Mészáros, P. ; Michelson, P. F. ; Mizuno, T. ; Monte, C. ; Monzani, M. E. ; Moretti, E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nakajima, H. ; Nakamori, T. ; Naumann-Godo, M. ; Nishino, S. ; Nolan, P. L. ; Norris, J. P. ; Nuss, E. ; Ohno, M. ; Ohsugi, T. ; Okumura, A. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Ozaki, M. ; Paciesas, W. S. ; Paneque, D. ; Panetta, J. H. ; Parent, D. ; Pelassa, V. ; Pepe, M. ; Pesce-Rollins, M. ; Petrosian, V. ; Piron, F. ; Porter, T. A. ; Preece, R. ; Racusin, J. L. ; Rainò, S. ; Rando, R. ; Rau, A. ; Razzano, M. ; Razzaque, S. ; Reimer, A. ; Reimer, O. ; Reposeur, T. ; Reyes, L. C. ; Ripken, J. ; Ritz, S. ; Roth, M. ; Ryde, F. ; Sadrozinski, H. F W ; Sander, A. ; Scargle, J. D. ; Schalk, T. L. ; Sgrò, C. ; Siskind, E. J. ; Smith, P. D. ; Spandre, G. ; Spinelli, P. ; Stamatikos, M. ; Stecker, F. W. ; Strickman, M. S. ; Suson, D. J. ; Tajima, H. ; Takahashi, H. ; Tanaka, T. ; Tanaka, Y. ; Thayer, J. B. ; Thayer, J. G. ; Tibaldo, L. ; Tierney, D. ; Toma, K. ; Torres, D. F. ; Tosti, G. ; Tramacere, A. ; Uchiyama, Y. ; Uehara, T. ; Usher, T. L. ; Vandenbroucke, J. ; Van Der Horst, A. J. ; Vasileiou, V. ; Vilchez, N. ; Vitale, V. ; Von Kienlin, A. ; Waite, A. P. ; Wang, P. ; Wilson-Hodge, C. ; Winer, B. L. ; Wood, K. S. ; Wu, X. F. ; Yamazaki, R. ; Yang, Z. ; Ylinen, T. ; Ziegler, M. / Detection of a spectral break in the extra hard component of GRB 090926A. In: Astrophysical Journal. 2011 ; Vol. 729, No. 2.
    @article{0365d32baff040eb8bfd9a9735e0feca,
    title = "Detection of a spectral break in the extra hard component of GRB 090926A",
    abstract = "We report on the observation of the bright, long gamma-ray burst, GRB090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB090926A 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.",
    keywords = "gamma-ray burst: individual (GRB 090926A)",
    author = "M. Ackermann and M. Ajello and K. Asano and M. Axelsson and L. Baldini and J. Ballet and G. Barbiellini and Baring, {M. G.} and D. Bastieri and K. Bechtol and R. Bellazzini and B. Berenji and Bhat, {P. N.} and E. Bissaldi and Blandford, {R. D.} and E. Bonamente and Borgland, {A. W.} and A. Bouvier and J. Bregeon and A. Brez and Briggs, {M. S.} and M. Brigida and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and S. Carrigan and Casandjian, {J. M.} and C. Cecchi and {\"O} {\cC}elik and V. Chaplin and E. Charles and A. Chekhtman and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and V. Connaughton and J. Conrad and S. Cutini and Dermer, {C. D.} and {De Angelis}, A. and {De Palma}, F. and Dingus, {B. L.} and {Do Couto E Silva}, E. and Drell, {P. S.} and R. Dubois and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and Focke, {W. B.} and M. Frailis and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and N. Gehrels and S. Germani and N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and A. Goldstein and J. Granot and J. Greiner and Grenier, {I. A.} and Grove, {J. E.} and S. Guiriec and D. Hadasch and Y. Hanabata and Harding, {A. K.} and K. Hayashi and M. Hayashida and E. Hays and D. Horan and Hughes, {R. E.} and R. Itoh and G. J{\'o}hannesson and Johnson, {A. S.} and Johnson, {W. N.} and T. Kamae and H. Katagiri and Jun Kataoka and Kippen, {R. M.} and J. Kn{\"o}dlseder and D. Kocevski and C. Kouveliotou and M. Kuss and J. Lande and L. Latronico and Lee, {S. H.} and {Llena Garde}, M. and F. Longo and F. Loparco and Lovellette, {M. N.} and P. Lubrano and A. Makeev and Mazziotta, {M. N.} and S. McBreen and McEnery, {J. E.} and S. McGlynn and C. Meegan and J. Mehault and P. M{\'e}sz{\'a}ros and Michelson, {P. F.} and T. Mizuno and C. Monte and Monzani, {M. E.} and E. Moretti and A. Morselli and Moskalenko, {I. V.} and S. Murgia and H. Nakajima and T. Nakamori and M. Naumann-Godo and S. Nishino and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and A. Okumura and N. Omodei and E. Orlando and Ormes, {J. F.} and M. Ozaki and Paciesas, {W. S.} and D. Paneque and Panetta, {J. H.} and D. Parent and V. Pelassa and M. Pepe and M. Pesce-Rollins and V. Petrosian and F. Piron and Porter, {T. A.} and R. Preece and Racusin, {J. L.} and S. Rain{\`o} and R. Rando and A. Rau and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and T. Reposeur and Reyes, {L. C.} and J. Ripken and S. Ritz and M. Roth and F. Ryde and Sadrozinski, {H. F W} and A. Sander and Scargle, {J. D.} and Schalk, {T. L.} and C. Sgr{\`o} and Siskind, {E. J.} and Smith, {P. D.} and G. Spandre and P. Spinelli and M. Stamatikos and Stecker, {F. W.} and Strickman, {M. S.} and Suson, {D. J.} and H. Tajima and H. Takahashi and T. Tanaka and Y. Tanaka and Thayer, {J. B.} and Thayer, {J. G.} and L. Tibaldo and D. Tierney and K. Toma and Torres, {D. F.} and G. Tosti and A. Tramacere and Y. Uchiyama and T. Uehara and Usher, {T. L.} and J. Vandenbroucke and {Van Der Horst}, {A. J.} and V. Vasileiou and N. Vilchez and V. Vitale and {Von Kienlin}, A. and Waite, {A. P.} and P. Wang and C. Wilson-Hodge and Winer, {B. L.} and Wood, {K. S.} and Wu, {X. F.} and R. Yamazaki and Z. Yang and T. Ylinen and M. Ziegler",
    year = "2011",
    month = "3",
    day = "10",
    doi = "10.1088/0004-637X/729/2/114",
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    volume = "729",
    journal = "Astrophysical Journal",
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    TY - JOUR

    T1 - Detection of a spectral break in the extra hard component of GRB 090926A

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Asano, K.

    AU - Axelsson, M.

    AU - Baldini, L.

    AU - Ballet, J.

    AU - Barbiellini, G.

    AU - Baring, M. G.

    AU - Bastieri, D.

    AU - Bechtol, K.

    AU - Bellazzini, R.

    AU - Berenji, B.

    AU - Bhat, P. N.

    AU - Bissaldi, E.

    AU - Blandford, R. D.

    AU - Bonamente, E.

    AU - Borgland, A. W.

    AU - Bouvier, A.

    AU - Bregeon, J.

    AU - Brez, A.

    AU - Briggs, M. S.

    AU - Brigida, M.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caraveo, P. A.

    AU - Carrigan, S.

    AU - Casandjian, J. M.

    AU - Cecchi, C.

    AU - Çelik, Ö

    AU - Chaplin, V.

    AU - Charles, E.

    AU - Chekhtman, A.

    AU - Chiang, J.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - Connaughton, V.

    AU - Conrad, J.

    AU - Cutini, S.

    AU - Dermer, C. D.

    AU - De Angelis, A.

    AU - De Palma, F.

    AU - Dingus, B. L.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Dubois, R.

    AU - Favuzzi, C.

    AU - Fegan, S. J.

    AU - Ferrara, E. C.

    AU - Focke, W. B.

    AU - Frailis, M.

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    PY - 2011/3/10

    Y1 - 2011/3/10

    N2 - We report on the observation of the bright, long gamma-ray burst, GRB090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB090926A 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.

    AB - We report on the observation of the bright, long gamma-ray burst, GRB090926A, by the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB090926A 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.

    KW - gamma-ray burst: individual (GRB 090926A)

    UR - http://www.scopus.com/inward/record.url?scp=79952159931&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=79952159931&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/729/2/114

    DO - 10.1088/0004-637X/729/2/114

    M3 - Article

    VL - 729

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 2

    M1 - 114

    ER -