A Spectral Analysis of Fermi-LLE Gamma-Ray Bursts

Abstract

Abstract The prompt emission of gamma-ray bursts remains mysterious since the mechanism is difficult to understand even though there are many more observations with the development of detection technology. Most of the gamma-ray bursts spectra show the Band shape, which consists of the low-energy spectral index α, the high-energy spectral index β, the peak energy E p , and the normalization of the spectrum. We present a systematic analysis of the spectral properties of 36 gamma-ray bursts (GRBs), which were detected by the Gamma-ray Burst Monitor (GBM) and simultaneously were also observed by the Large Area Telescope (LAT) and the LAT Low Energy (LLE) detector on the Fermi satellite. We performed a detailed time-resolved spectral analysis for all of the bursts in our sample. We found that the time-resolved spectrum at peak flux can be well fitted by the empirical Band function for each burst in our sample. Moreover, the evolution patterns of α and E p have been carried for statistical analysis and the parameter correlations have been obtained such as E p –F, α–F, and E p –α, all of them are presented by performing a detailed time-resolved spectral analysis. We also demonstrated that the two strong positive correlations α–F and E p –α for some bursts originate from nonphysical selection effects through simulation.