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., 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., Celik, O., Chaplin, V., Charles, E., Chekhtman, A., Chiang, J., Ciprini, S., Claus, R., Cohen-Tanugi, J., Connaughton, V., Conrad, J., Cutini, S., Dermer, C., de Angelis, A., de Palma, F., Dingus, B., do Couto e Silva, E., Drell, P.S., Dubois, R., Favuzzi, C., Fegan, S., Ferrara, E.C., Focke, W.B., Frailis, M., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Gehrels, N., Giglietto, N., Giordano, N. and Vilchez, N. (2011) Detection of a spectral break in the extra hard component of GRB 090926A. The Astrophysical Journal, 729 (2). ISSN 0004-637X
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We report on the observation of the bright, long gamma-ray burst,GRB 090926A, by the Gamma-ray Burst Monitor (GBM) and Large Area Tele-scope (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 GRBs, 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.
Item Type Article
Identification Number 10.1088/0004-637X/729/2/114
Additional information ‘In these times, during the rise in the popularity of institutional repositories, the Society does not forbid authors from depositing their work in such repositories. However, the AAS regards the deposit of scholarly work in such repositories to be a decision of the individual scholar, as long as the individual's actions respect the diligence of the journals and their reviewers.’ Original article can be found at: http://iopscience.iop.org/ Copyright American Astronomical Society
Keywords gamma rays: bursts
Date Deposited 15 May 2025 11:57
Last Modified 02 Feb 2026 00:02

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