Identification of Two categories of optically bright gamma-ray bursts
Abstract
We present the results of a systematical analysis of the intrinsic optical afterglow light curves for a complete sample of gamma-ray bursts (GRBs) observed in the period from Feb. 1997 to Aug. 2005. These light curves are generally well-sampled, with at least four detections in the band. The redshifts of all the bursts in the sample are available. We derive the intrinsic band afterglow lightcurves (luminosity versus time within the cosmic proper rest frame) for these GRBs, and discover a fact that they essentially follow two universal tracks after 2 hours since the GRB triggers. The optical luminosities at 1 day show a clear bimodal distribution, peaking at 1.4*10^{46} ergs~s^{-1} for the luminous group and 5.3*10^{44} ergs~s^{-1} for the dim group. About 75% of the GRBs are in the luminous group, and the other 25% belong to the dim group. While the luminous group has a wide range of redshift distribution, the bursts in the dim group all appear at a redshift lower than 1.1.
Keywords
Cite
@article{arxiv.astro-ph/0508510,
title = {Identification of Two categories of optically bright gamma-ray bursts},
author = {Enwei Liang and Bing Zhang},
journal= {arXiv preprint arXiv:astro-ph/0508510},
year = {2009}
}
Comments
10 pages, 2 figures, emulateapj style, accepted for publication by ApJ Letters