2006/08/31 by Shiho Kobayashi, Bing Zhang · 9 citations
Earth and Planetary Sciences · Physics and Astronomy · #Afterglow #Astrophysics and Cosmic Phenomena #Context (archaeology) #Earth Systems and Cosmic Evolution #Ejecta #Gamma-ray burst #Gamma-ray bursts and supernovae #Light curve #Shock (circulatory) #astro-ph
paper · pdf · doi:10.1086/510203
published as Astrophys.J.655:973-979,2007 · 22 pages, 7 figures, accepted for publication in ApJ
arxiv created 2006/10/16 · openalex publication_date 2007/01/23 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We discuss the reference time t 0 of afterglow light curves in the context of the standard internal-external shock model. The decay index of early afterglow is very sensitive to the reference time one chooses. In order to understand the nature of early afterglow, it is essential to take a correct reference time. Our simple analytic model provides a framework for understanding special relativistic effects involved in early afterglow phase. We evaluate light curves of reverse shock emission as well as those of forward shock emission, based on full hydrodynamic calculations. We show that the reference time does not shift significantly even in the thick-shell case. For external shock emission components, measuring times from the beginning of the prompt emission is a good approximation and it does not cause an early steep decay. In the thin-shell case, the energy transfer time from fireball ejecta to ambient medium typically extends to thousands of seconds. This might be related to the shallow decay phases observed in early X-ray afterglow at least for some bursts.