A Study Of Gamma-Ray Burst Durations

The central engine of Gamma-Ray Bursts (GRBs) is one of the essential problems to understand the GRB phenomena. The duration of the gamma-ray emission is an important observational data of GRBs. With data from CGRO/BATSE’s sky survey for GRBs in1991, it is found that the duration distribution is bimodal, hence two types of GRBs, i.e., long vs. short GRBs with a division at2seconds, were proposed. They may correspond to two kinds of origins for GRBs, i.e., the collapse of massive stars&the merger of two compact objects. However, the observations of Swift satellite (launched in2004) challenge this classification. Fermi satellite (launched in2008) makes observations in a broad energy band. During my study for the Master degree, I focused on the observed GRB durations with different instruments and in different energy band for one instrument, in order to reveal the selection effect of GRBs’duration distribution and giving a new understanding of the duration for short GRBs. In Chapter1, we summarize the progress for the GRB field in recent years, especially in the Fermi and Swift era. In Chapter2, we present the results of our spectra and temporal analysis for a joint Swift/BAT—Fermi/GBM GRB sample. We find that in one GRB of BAT detector, long GRB is much longer and short GRB is less shorter, which means the duration depends on the instruments. Besides, we also made joint analysis for Swift/BAT—Fermi/GBM GRB sample, and test the corresponding relation of spectra energy. In Chapter3, we make a systematical analysis of the duration distributions with different instruments to reveal the selection effect of the distributions. With data observed with Fermi/GBM, we investigate the burst duration distributions in different energy bands and the energy dependence of the duration. In Chapter4, we introduce a new progress of GRB’s classification by researching the complexity of light curves. We use a new method to calculate the complexity to measure the light curves of two types of GRBs, and search whether there are some gathering characters between two kinds of GRBs&the existence between complexity and T90or not Summarization and a brief discussion are presented in Chapter5.