Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission

A. A. Abdo; M. Ackermann; M. Ajello; K. Asano; W. B. Atwood; 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. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. S. Briggs; M. Brigida; P. Bruel; J. M. Burgess; D. N. Burrows; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; C. Cecchi; Ö Çelik; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; L. R. Cominsky; V. Connaughton; J. Conrad; S. Cutini; V. D'Elia; C. D. Dermer; A. De Angelis; F. De Palma; S. W. Digel; B. L. Dingus; E. Do Couto E Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; J. Finke; G. Fishman; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; N. Gehrels; S. Germani; G. Giavitto; B. Giebels; N. Giglietto; F. Giordano; T. Glanzman; G. Godfrey; A. Goldstein; J. Granot; J. Greiner; I. A. Grenier; J. E. Grove; L. Guillemot; S. Guiriec; Y. Hanabata; A. K. Harding; M. Hayashida; E. Hays; D. Horan; R. E. Hughes; M. S. Jackson; G. Jóhannesson; A. S. Johnson; R. P. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; R. M. Kippen; J. Knödlseder; D. Kocevski; N. Komin; C. Kouveliotou; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; M. N. Mazziotta; S. McBreen; J. E. McEnery; S. McGlynn; C. Meegan; P. Mészros; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; E. Moretti; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; P. L. Nolan; J. P. Norris; E. Nuss; M. Ohno; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; W. S. Paciesas; D. Paneque; J. H. Panetta; V. Pelassa; M. Pepe; M. Pesce-Rollins; V. Petrosian; F. Piron; T. A. Porter; R. Preece; S. Rainò; R. Rando; A. Rau; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; T. Reposeur; S. Ritz; L. S. Rochester; A. Y. Rodriguez; P. W.A. Roming; M. Roth; F. Ryde; H. F.W. Sadrozinski; D. Sanchez; A. Sander; P. M. Saz Parkinson; J. D. Scargle; T. L. Schalk; C. Sgrò; E. J. Siskind; P. D. Smith; P. Spinelli; M. Stamatikos; F. W. Stecker; G. Stratta; M. S. Strickman; D. J. Suson; C. A. Swenson; H. Tajima; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. Uehara; T. L. Usher; 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; R. Yamazaki; T. Ylinen; M. Ziegler

doi:10.1088/0004-637X/706/1/L138

Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission

A. A. Abdo, M. Ackermann, M. Ajello, K. Asano, W. B. Atwood, 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. D. Bloom, E. Bonamente, A. W. BorglandA. Bouvier, J. Bregeon, A. Brez, M. S. Briggs, M. Brigida, P. Bruel, J. M. Burgess, D. N. Burrows, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, Ö Çelik, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, L. R. Cominsky, V. Connaughton, J. Conrad, S. Cutini, V. D'Elia, C. D. Dermer, A. De Angelis, F. De Palma, S. W. Digel, B. L. Dingus, E. Do Couto E Silva, P. S. Drell, R. Dubois, D. Dumora, C. Farnier, C. Favuzzi, S. J. Fegan, J. Finke, G. Fishman, W. B. Focke, P. Fortin, M. Frailis, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, N. Gehrels, S. Germani, G. Giavitto, B. Giebels, N. Giglietto, F. Giordano, T. Glanzman, G. Godfrey, A. Goldstein, J. Granot, J. Greiner, I. A. Grenier, J. E. Grove, L. Guillemot, S. Guiriec, Y. Hanabata, A. K. Harding, M. Hayashida, E. Hays, D. Horan, R. E. Hughes, M. S. Jackson, G. Jóhannesson, A. S. Johnson, R. P. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, J. Kataoka, N. Kawai, M. Kerr, R. M. Kippen, J. Knödlseder, D. Kocevski, N. Komin, C. Kouveliotou, M. Kuss, J. Lande, L. Latronico, M. Lemoine-Goumard, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, A. Makeev, M. N. Mazziotta, S. McBreen, J. E. McEnery, S. McGlynn, C. Meegan, P. Mészros, C. Meurer, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, W. S. Paciesas, D. Paneque, J. H. Panetta, V. Pelassa, M. Pepe, M. Pesce-Rollins, V. Petrosian, F. Piron, T. A. Porter, R. Preece, S. Rainò, R. Rando, A. Rau, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, L. S. Rochester, A. Y. Rodriguez, P. W.A. Roming, M. Roth, F. Ryde, H. F.W. Sadrozinski, D. Sanchez, A. Sander, P. M. Saz Parkinson, J. D. Scargle, T. L. Schalk, C. Sgrò, E. J. Siskind, P. D. Smith, P. Spinelli, M. Stamatikos, F. W. Stecker, G. Stratta, M. S. Strickman, D. J. Suson, C. A. Swenson, H. Tajima, H. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, G. Tosti, A. Tramacere, Y. Uchiyama, T. Uehara, T. L. Usher, 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, R. Yamazaki, T. Ylinen, M. Ziegler

School of Advanced Science and Engineering

Research output: Contribution to journal › Article › peer-review

388 Citations (Scopus)

Abstract

We report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ∼ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t ^-1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4 ^+2.7 _-3.5 GeV. This event arrived 82 s after the GBM trigger and ∼ 50 s after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light.

Original language	English
Pages (from-to)	L138-L144
Journal	Astrophysical Journal
Volume	706
Issue number	1 PART 2
DOIs	https://doi.org/10.1088/0004-637X/706/1/L138
Publication status	Published - 2009

Keywords

Gamma rays: bursts

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1088/0004-637X/706/1/L138

Cite this

Abdo, A. A., Ackermann, M., Ajello, M., Asano, K., Atwood, W. B., 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., Bloom, E. D., Bonamente, E., ... Ziegler, M. (2009). Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission. Astrophysical Journal, 706(1 PART 2), L138-L144. https://doi.org/10.1088/0004-637X/706/1/L138

Abdo, AA, Ackermann, M, Ajello, M, Asano, K, Atwood, WB, Axelsson, M, Baldini, L, Ballet, J, Barbiellini, G, Baring, MG, Bastieri, D, Bechtol, K, Bellazzini, R, Berenji, B, Bhat, PN, Bissaldi, E, Blandford, RD, Bloom, ED, Bonamente, E, Borgland, AW, Bouvier, A, Bregeon, J, Brez, A, Briggs, MS, Brigida, M, Bruel, P, Burgess, JM, Burrows, DN, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Casandjian, JM, Cecchi, C, Çelik, Ö, Chekhtman, A, Cheung, CC, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Cominsky, LR, Connaughton, V, Conrad, J, Cutini, S, D'Elia, V, Dermer, CD, De Angelis, A, De Palma, F, Digel, SW, Dingus, BL, Do Couto E Silva, E, Drell, PS, Dubois, R, Dumora, D, Farnier, C, Favuzzi, C, Fegan, SJ, Finke, J, Fishman, G, Focke, WB, Fortin, P, Frailis, M, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gehrels, N, Germani, S, Giavitto, G, Giebels, B, Giglietto, N, Giordano, F, Glanzman, T, Godfrey, G, Goldstein, A, Granot, J, Greiner, J, Grenier, IA, Grove, JE, Guillemot, L, Guiriec, S, Hanabata, Y, Harding, AK, Hayashida, M, Hays, E, Horan, D, Hughes, RE, Jackson, MS, Jóhannesson, G, Johnson, AS, Johnson, RP, Johnson, WN, Kamae, T, Katagiri, H, Kataoka, J, Kawai, N, Kerr, M, Kippen, RM, Knödlseder, J, Kocevski, D, Komin, N, Kouveliotou, C, Kuss, M, Lande, J, Latronico, L, Lemoine-Goumard, M, Longo, F, Loparco, F, Lott, B, Lovellette, MN, Lubrano, P, Madejski, GM, Makeev, A, Mazziotta, MN, McBreen, S, McEnery, JE, McGlynn, S, Meegan, C, Mészros, P, Meurer, C, Michelson, PF, Mitthumsiri, W, Mizuno, T, Moiseev, AA, Monte, C, Monzani, ME, Moretti, E, Morselli, A, Moskalenko, IV, Murgia, S, Nakamori, T, Nolan, PL, Norris, JP, Nuss, E, Ohno, M, Ohsugi, T, Omodei, N, Orlando, E, Ormes, JF, Paciesas, WS, Paneque, D, Panetta, JH, Pelassa, V, Pepe, M, Pesce-Rollins, M, Petrosian, V, Piron, F, Porter, TA, Preece, R, Rainò, S, Rando, R, Rau, A, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reposeur, T, Ritz, S, Rochester, LS, Rodriguez, AY, Roming, PWA, Roth, M, Ryde, F, Sadrozinski, HFW, Sanchez, D, Sander, A, Saz Parkinson, PM, Scargle, JD, Schalk, TL, Sgrò, C, Siskind, EJ, Smith, PD, Spinelli, P, Stamatikos, M, Stecker, FW, Stratta, G, Strickman, MS, Suson, DJ, Swenson, CA, Tajima, H, Takahashi, H, Tanaka, T, Thayer, JB, Thayer, JG, Thompson, DJ, Tibaldo, L, Torres, DF, Tosti, G, Tramacere, A, Uchiyama, Y, Uehara, T, Usher, TL, Van Der Horst, AJ, Vasileiou, V, Vilchez, N, Vitale, V, Von Kienlin, A, Waite, AP, Wang, P, Wilson-Hodge, C, Winer, BL, Wood, KS, Yamazaki, R, Ylinen, T & Ziegler, M 2009, 'Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission', Astrophysical Journal, vol. 706, no. 1 PART 2, pp. L138-L144. https://doi.org/10.1088/0004-637X/706/1/L138

@article{f04d1bef9cf44d7080d2e01510303b65,

title = "Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission",

abstract = "We report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ∼ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t -1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4 +2.7 -3.5 GeV. This event arrived 82 s after the GBM trigger and ∼ 50 s after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light.",

keywords = "Gamma rays: bursts",

author = "Abdo, {A. A.} and M. Ackermann and M. Ajello and K. Asano and Atwood, {W. B.} 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 Bloom, {E. 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 Burgess, {J. M.} and Burrows, {D. N.} and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and C. Cecchi and {\"O} {\c C}elik and A. Chekhtman and Cheung, {C. C.} and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and Cominsky, {L. R.} and V. Connaughton and J. Conrad and S. Cutini and V. D'Elia and Dermer, {C. D.} and {De Angelis}, A. and {De Palma}, F. and Digel, {S. W.} and Dingus, {B. L.} and {Do Couto E Silva}, E. and Drell, {P. S.} and R. Dubois and D. Dumora and C. Farnier and C. Favuzzi and Fegan, {S. J.} and J. Finke and G. Fishman and Focke, {W. B.} and P. Fortin and M. Frailis and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and N. Gehrels and S. Germani and G. Giavitto and B. Giebels and N. Giglietto and F. Giordano and T. Glanzman and G. Godfrey and A. Goldstein and J. Granot and J. Greiner and Grenier, {I. A.} and Grove, {J. E.} and L. Guillemot and S. Guiriec and Y. Hanabata and Harding, {A. K.} and M. Hayashida and E. Hays and D. Horan and Hughes, {R. E.} and Jackson, {M. S.} and G. J{\'o}hannesson and Johnson, {A. S.} and Johnson, {R. P.} and Johnson, {W. N.} and T. Kamae and H. Katagiri and J. Kataoka and N. Kawai and M. Kerr and Kippen, {R. M.} and J. Kn{\"o}dlseder and D. Kocevski and N. Komin and C. Kouveliotou and M. Kuss and J. Lande and L. Latronico and M. Lemoine-Goumard and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and Madejski, {G. M.} and A. Makeev and Mazziotta, {M. N.} and S. McBreen and McEnery, {J. E.} and S. McGlynn and C. Meegan and P. M{\'e}szros and C. Meurer and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and E. Moretti and A. Morselli and Moskalenko, {I. V.} and S. Murgia and T. Nakamori and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and N. Omodei and E. Orlando and Ormes, {J. F.} and Paciesas, {W. S.} and D. Paneque and Panetta, {J. H.} and V. Pelassa and M. Pepe and M. Pesce-Rollins and V. Petrosian and F. Piron and Porter, {T. A.} and R. Preece 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 S. Ritz and Rochester, {L. S.} and Rodriguez, {A. Y.} and Roming, {P. W.A.} and M. Roth and F. Ryde and Sadrozinski, {H. F.W.} and D. Sanchez and A. Sander and {Saz Parkinson}, {P. M.} and Scargle, {J. D.} and Schalk, {T. L.} and C. Sgr{\`o} and Siskind, {E. J.} and Smith, {P. D.} and P. Spinelli and M. Stamatikos and Stecker, {F. W.} and G. Stratta and Strickman, {M. S.} and Suson, {D. J.} and Swenson, {C. A.} and H. Tajima and H. Takahashi and T. Tanaka and Thayer, {J. B.} and Thayer, {J. G.} and Thompson, {D. J.} and L. Tibaldo and Torres, {D. F.} and G. Tosti and A. Tramacere and Y. Uchiyama and T. Uehara and Usher, {T. L.} 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 R. Yamazaki and T. Ylinen and M. Ziegler",

year = "2009",

doi = "10.1088/0004-637X/706/1/L138",

language = "English",

volume = "706",

pages = "L138--L144",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

number = "1 PART 2",

}

TY - JOUR

T1 - Fermi observations of GRB 090902b

T2 - A distinct spectral component in the prompt and delayed emission

AU - Abdo, A. A.

AU - Ackermann, M.

AU - Ajello, M.

AU - Asano, K.

AU - Atwood, W. B.

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 - Bloom, E. 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 - Burgess, J. M.

AU - Burrows, D. N.

AU - Buson, S.

AU - Caliandro, G. A.

AU - Cameron, R. A.

AU - Caraveo, P. A.

AU - Casandjian, J. M.

AU - Cecchi, C.

AU - Çelik, Ö

AU - Chekhtman, A.

AU - Cheung, C. C.

AU - Chiang, J.

AU - Ciprini, S.

AU - Claus, R.

AU - Cohen-Tanugi, J.

AU - Cominsky, L. R.

AU - Connaughton, V.

AU - Conrad, J.

AU - Cutini, S.

AU - D'Elia, V.

AU - Dermer, C. D.

AU - De Angelis, A.

AU - De Palma, F.

AU - Digel, S. W.

AU - Dingus, B. L.

AU - Do Couto E Silva, E.

AU - Drell, P. S.

AU - Dubois, R.

AU - Dumora, D.

AU - Farnier, C.

AU - Favuzzi, C.

AU - Fegan, S. J.

AU - Finke, J.

AU - Fishman, G.

AU - Focke, W. B.

AU - Fortin, P.

AU - Frailis, M.

AU - Fukazawa, Y.

AU - Funk, S.

AU - Fusco, P.

AU - Gargano, F.

AU - Gehrels, N.

AU - Germani, S.

AU - Giavitto, G.

AU - Giebels, B.

AU - Giglietto, N.

AU - Giordano, F.

AU - Glanzman, T.

AU - Godfrey, G.

AU - Goldstein, A.

AU - Granot, J.

AU - Greiner, J.

AU - Grenier, I. A.

AU - Grove, J. E.

AU - Guillemot, L.

AU - Guiriec, S.

AU - Hanabata, Y.

AU - Harding, A. K.

AU - Hayashida, M.

AU - Hays, E.

AU - Horan, D.

AU - Hughes, R. E.

AU - Jackson, M. S.

AU - Jóhannesson, G.

AU - Johnson, A. S.

AU - Johnson, R. P.

AU - Johnson, W. N.

AU - Kamae, T.

AU - Katagiri, H.

AU - Kataoka, J.

AU - Kawai, N.

AU - Kerr, M.

AU - Kippen, R. M.

AU - Knödlseder, J.

AU - Kocevski, D.

AU - Komin, N.

AU - Kouveliotou, C.

AU - Kuss, M.

AU - Lande, J.

AU - Latronico, L.

AU - Lemoine-Goumard, M.

AU - Longo, F.

AU - Loparco, F.

AU - Lott, B.

AU - Lovellette, M. N.

AU - Lubrano, P.

AU - Madejski, G. M.

AU - Makeev, A.

AU - Mazziotta, M. N.

AU - McBreen, S.

AU - McEnery, J. E.

AU - McGlynn, S.

AU - Meegan, C.

AU - Mészros, P.

AU - Meurer, C.

AU - Michelson, P. F.

AU - Mitthumsiri, W.

AU - Mizuno, T.

AU - Moiseev, A. A.

AU - Monte, C.

AU - Monzani, M. E.

AU - Moretti, E.

AU - Morselli, A.

AU - Moskalenko, I. V.

AU - Murgia, S.

AU - Nakamori, T.

AU - Nolan, P. L.

AU - Norris, J. P.

AU - Nuss, E.

AU - Ohno, M.

AU - Ohsugi, T.

AU - Omodei, N.

AU - Orlando, E.

AU - Ormes, J. F.

AU - Paciesas, W. S.

AU - Paneque, D.

AU - Panetta, J. H.

AU - Pelassa, V.

AU - Pepe, M.

AU - Pesce-Rollins, M.

AU - Petrosian, V.

AU - Piron, F.

AU - Porter, T. A.

AU - Preece, R.

AU - Rainò, S.

AU - Rando, R.

AU - Rau, A.

AU - Razzano, M.

AU - Razzaque, S.

AU - Reimer, A.

AU - Reimer, O.

AU - Reposeur, T.

AU - Ritz, S.

AU - Rochester, L. S.

AU - Rodriguez, A. Y.

AU - Roming, P. W.A.

AU - Roth, M.

AU - Ryde, F.

AU - Sadrozinski, H. F.W.

AU - Sanchez, D.

AU - Sander, A.

AU - Saz Parkinson, P. M.

AU - Scargle, J. D.

AU - Schalk, T. L.

AU - Sgrò, C.

AU - Siskind, E. J.

AU - Smith, P. D.

AU - Spinelli, P.

AU - Stamatikos, M.

AU - Stecker, F. W.

AU - Stratta, G.

AU - Strickman, M. S.

AU - Suson, D. J.

AU - Swenson, C. A.

AU - Tajima, H.

AU - Takahashi, H.

AU - Tanaka, T.

AU - Thayer, J. B.

AU - Thayer, J. G.

AU - Thompson, D. J.

AU - Tibaldo, L.

AU - Torres, D. F.

AU - Tosti, G.

AU - Tramacere, A.

AU - Uchiyama, Y.

AU - Uehara, T.

AU - Usher, T. L.

AU - Van Der Horst, A. J.

AU - Vasileiou, V.

AU - Vilchez, N.

AU - Vitale, V.

AU - Von Kienlin, A.

AU - Waite, A. P.

AU - Wang, P.

AU - Wilson-Hodge, C.

AU - Winer, B. L.

AU - Wood, K. S.

AU - Yamazaki, R.

AU - Ylinen, T.

AU - Ziegler, M.

PY - 2009

Y1 - 2009

N2 - We report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ∼ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t -1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4 +2.7 -3.5 GeV. This event arrived 82 s after the GBM trigger and ∼ 50 s after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light.

AB - We report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ∼ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t -1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4 +2.7 -3.5 GeV. This event arrived 82 s after the GBM trigger and ∼ 50 s after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light.

KW - Gamma rays: bursts

UR - http://www.scopus.com/inward/record.url?scp=77649210676&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77649210676&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/706/1/L138

DO - 10.1088/0004-637X/706/1/L138

M3 - Article

AN - SCOPUS:77649210676

VL - 706

SP - L138-L144

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 PART 2

ER -

Fermi observations of GRB 090902b: A distinct spectral component in the prompt and delayed emission

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