GBM Long and Short GRB Lightcurve Decomposition Analysis

The Gamma-ray Burst duration distribution is bi-modal with a minimum around 2 s suggesting that there are two separate populations. The GRB time profiles, believed to be the result of internal shocks, reflect the activity of the central engine. A systematic study of the GRB temporal profiles was carried out with a view to understanding the possible differences in the properties of the central engine in the two populations of GRBs. We analyse the temporal profiles of gamma-ray bursts detected by the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope. We deconvolve these profiles into pulses superposed on a quadratic background. The basic pulse shapes are fitted to lognormal functions. It is found that the distributions of rise as well as decay times, their full width at half maximum and the time intervals between successive pulses for long and short GRBs are distinct and each follows a lognormal distribution. We identify several differences in the temporal properties of long and short bursts which in turn reflect the differences in the activities of central engines of the two types of GRBs.