An analysis of the durations of Swift Gamma-Ray Bursts

Abstract

We report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. For 95 GRBs with known redshift, we show that the observed durations have two lognormal distributions that are clearly divided at $T_{90}\simeq 2$ s. This is consistent with the earlier BATSE results. The intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value and the distribution exhibits a narrower width compared with the observed one. We find that the intrinsic distributions of long GRBs between Swift and pre-Swift are significantly different particularly in the width and the median value. In addition, the Swift data exhibit a wider dynamic range of duration. Our present study not only confirms the spectra of short GRBs are in general harder than the long GRBs in the observer frame but also shows this trend becomes weaker in the source frame.

5 pages, 4 figures and 2 table; Accepted to A&A with minor changes; Note that our previously main conclusions are unchanged

References in corpus (8)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• A Complete Catalog of Swift GRB Spectra and Durations: Demise of a Physical Origin for Pre-Swift High-Energy Correlations
• Astrophysics: A burst of new ideas
• A new definition of the intermediate group of gamma-ray bursts
• Post-Launch Analysis of Swift's Gamma-Ray Burst Detection Sensitivity
• Further Study of the Gamma-Ray Bursts Duration Distribution
• Revisiting the characteristics of the spectral lags in short gamma-ray bursts
• The Swift satellite and redshifts of long gamma-ray bursts

Cited by in corpus (1)

• Gamma-Ray Bursts as a Threat to Life on Earth