共动系中伽玛暴峰值能量的分布及其与光度的关系

The Peak Energy Distribution of the GRBs in the Co-moving Frame and Its Relation with Luminosity

伽玛暴νfν谱的峰值能量E_p是伽玛暴的一个很重要的观测物理量,观测系中伽玛暴νf_ν谱的峰值能量Ep分布很宽.根据各向同性光度L_(iso)、初始洛伦兹因子Γ_0和暴源系中峰值能量E_p,z之间的关系式估算伽玛暴的初始洛伦兹因子Γ_0,再把伽玛暴νf_ν谱的峰值能量E_p和光度L_(iso)修正到共动坐标系,发现共动系中峰值能量的分布还是很宽.这意味着观测系中E_p的宽分布可能是伽玛暴的真实物理分布.检验了共动坐标系中光度和峰值能量之间的关系,发现它们之间仍然存在相关性.最后,进一步对伽玛暴的辐射物理进行限制,认为共动坐标系中峰值能量分布很宽可能是由于辐射电子的洛伦兹因子γ_e分布很宽.

Gamma-ray bursts （GRBs） are one of the most violent events in the uni- verse. The observations of GRBs can be all-time and in all electromagnetic wavelength bands after over fourty-years development. The Fermi Gamma-Ray Space Telescope （Fermi） was launched into orbit by NASA （National Aeronautics and Space Adminis- tration） from the Cape Canaveral on 2008 June 11, which can measure the spectra in a very wide energy band （from 8 keV to more than 300 GeV）, and can be used to prompt- ly record the radiations of GRBs. The observations with the Fermi/GBM （Gamma-Ray Burst Monitor） have dramatically deepened our knowledge of the broad-band spectra of GRBs. The peak energy Ep in the vfv spectrum of GRBs is an important observational quantity, which distributes widely among GRBs. In this paper, we have analyzed the Ep distribution for a sample of the redshifts-known GRBs observed with Fermi/GBM from June 2008 to December 2016. The catalog contains 98 GRBs. We estimate the value of the initial Lorentz factor F0 based on the multi-variable correlation among the isotropic gamma-ray luminosity Liso, the cosmological rest-frame peak energy Ep,z, and the initial Lorentz factor F0. Then both Ep and Liso are corrected to the GRB co-moving frame. We find that the Ep distribution of GRBs is broad too, which means that the wide distribution of the peak energy Ep in the observer＇s frame might be an intrinsic property of GRBs, and in the co-moving frame the isotropic gamma-ray en- ergy and the peak energy are still correlated. We also constrain the possible radiation mechanisms of GRBs, and suggest that the broad Ep distribution may result from the broad distribution of the Lorentz factor γe of the electrons among different sources.