Statistical Distinctions Of The Spectrum And Light Curves Between Two Classes Of Gamma-Ray Bursts

We first summarize the observational features of gamma-ray bursts (GRBs) obtained in past three decades, including temporal structures,energy spectra and spatial distribution. GRBs display very diverse temporal structures, their durations spanning from the shortest < 1s to the longest 1000s, the average is about 15s. The emission has been measured over a broad band of energies from 10keV to 10MeV, there are the absorption and emission lines in some GRBs spectra. The spatial distribution of GRBs appears isotropic. Second, we discuss the various radiation mechanisms and the formation of the spectra of GRBs based on the assumption that GRBs sources are neutron stars. Because the magnetic field is very strong near the neutron star surface, we review the radiation processes in strong magnetic field, including synchrotron radiation and absorption, one-photon pair production and annihilation, two-photon pair production and annihilation, Compton scattering and bremsstrahlung. We also discuss some main radiation mechanisms of GRB, i.e. synchrotron radiation, bremsstrahlung and inverse Compton scattering, and discuss some probable mechanisms for producing the cyclotron absorption lines and emission lines. In addition, we introduce the recent observational result obtained by the burst and transient source experiment (BATSE) on the Compton Gamma-ray Observatory. They show that the distribution of the gamma-ray burst sources is isotropic in argular direction but nonuniform, and indicate that the bursts located at the cosmological distance. We discuss the models about the origin of GRBs, including the neutron star merging model and black hole accreting model etc. We also discuss the possibility that there may be two different kinds of GRBs. Finally, we introduce the new breakthrough in GRBs research :afterglows being observed.Thanks to the prominent operations of BeppoSAX satellite, X-ray, optical and even radio afterglows from several GRBs were observed recently, leading to a great breakthrough in the field. These observations strongly suggest a cosmological origin for GRBs and the so-called fireball model is favored currently.Then, we present the results of our studies on the statistical distinctions of the light curves between two classes of GRBs.