Characteristics of the curvature effect of uniform jets or spherical fireballs.pdf

A Mon. Not. R. Astron. Soc. ????, 1–12 (2004) Printed 5 February 2008 (MN LT X style file v2.2) E Characteristics of the curvature effect of uniform jets or spherical fireballs 5 0 R.-J. Lu1,2,3,4 , Y.-P. Qin1,2,4 0 2 1 National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, g u P. O. Box 110, Kunming 650011, China A 2Physics Department, Guangxi University, Nanning, Guangxi 530004, P.R. China 8 3 2 The Graduate School of the Chinese Academy of Sciences; luruijing@126.com 4E-mail:luruijing@126.com, ypqin@ 2 v 7 3 Accepted ????. Received ????; in original form 2005 August 08 5 8 0 5 ABSTRACT 0 / h Qin et al. (2004) have derived a formula of count rates based on a model p - of highly symmetric expanding fireballs, where the Doppler effect is the key o r factor to be concerned. In this paper, we employ the formula to both the Qin t s model and the uniform jet model to study how the rising timescale, ∆τθ,r , a : v and the decay timescale, ∆τθ,d , of a local pulse affect the light curve of GRBs. i X Our analysis shows that they do make contributions to both rising and decay r a portions of the light curve of GRBs. Associated with a local pulse with both rising and decay portions, the light curve of GRBs in the rising portion is