Spectral cutoffs of Fermi-LAT GRBs 080916C and 090926A  

作　　者：Biao Li Zhuo Li 

机构地区：[1]Department of Astronomy/Kavli Institute for Astronomy and Astrophysics,Peking University,Beijing 100871,China [2]Key Laboratory for the Structure and Evolution of Celestial Objects,Chinese Academy ofSciences,Kunming 650011,China

出　　处：《Research in Astronomy and Astrophysics》2012年第11期1519-1525,共7页天文和天体物理学研究（英文版）

基　　金：supported by the Open Research Program of the Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences

摘　　要：It is expected that there should be a spectral cutoff at the high energy end of emission from a prompt gamma-ray burst （GRB）, due to, e.g. γγ absorption and/or a high energy cutoff in the electron distribution. We analyze the spectral data of Fermi- LAT detected GRBs 080916C and 090926A, aiming at locating the spectral cutoff. By assuming that the prompt GRB spectrum at the high energy end is a power law with an exponential cutoff, our analysis finds that the cutoff energy Ecutoff depends on the photon index/3 and the cutoff occurs at very high energy, Ecutoff = 161＋533 GeV in GRB 080916C and Ecutoff ≥ 100 GeV （forβ ≈-2.3） in GRB 090926A. Such high energy photons, if they exist, may disfavor the synchrotron origin and need alternative generation mechanisms.It is expected that there should be a spectral cutoff at the high energy end of emission from a prompt gamma-ray burst （GRB）, due to, e.g. γγ absorption and/or a high energy cutoff in the electron distribution. We analyze the spectral data of Fermi- LAT detected GRBs 080916C and 090926A, aiming at locating the spectral cutoff. By assuming that the prompt GRB spectrum at the high energy end is a power law with an exponential cutoff, our analysis finds that the cutoff energy Ecutoff depends on the photon index/3 and the cutoff occurs at very high energy, Ecutoff = 161＋533 GeV in GRB 080916C and Ecutoff ≥ 100 GeV （forβ ≈-2.3） in GRB 090926A. Such high energy photons, if they exist, may disfavor the synchrotron origin and need alternative generation mechanisms.

关 键 词：gamma-rays： bursts -- acceleration of particles 

分 类 号：P172.3[天文地球—天文学] TP75[自动化与计算机技术—检测技术与自动化装置]