Optical Limits on Precursor Emission from Gamma-Ray Bursts with Known Redshift
Abstract
Making use of virtual observatory data, we present the first comprehensive sample of optical observations conducted before the explosion times of all gamma-ray bursts (GRBs) with known redshifts. In total, the fields of 11 such GRBs were observed by the Near-Earth Asteroid Tracking (NEAT) program from years to hours before the bursts. Though the typical limiting magnitudes from these observations are R~20 mag, we find no evidence for a significant detection of a precursor. The deepest non-detection of precursor emission is from GRB 030329, reaching down to an absolute B-band magnitude of M_B -18 mag from 6--1500 days (restframe) before the burst. This is of comparable brightness to supernovae, which, in some scenarios for GRB progenitors, are predicted to pre-date a GRB on similar timescales. Since sources cannot be localized to better than ~500 milliarcsecond (3 sigma) with current large-area surveys, unrelated supernovae or AGN activity in GRB hosts could be mistaken for genuine precursor emission. This possibility motivates the need for not only deep wide-field imaging, but imaging at high spatial resolution.
Cite
@article{arxiv.astro-ph/0304169,
title = {Optical Limits on Precursor Emission from Gamma-Ray Bursts with Known Redshift},
author = {C. Blake and J. S. Bloom},
journal= {arXiv preprint arXiv:astro-ph/0304169},
year = {2009}
}
Comments
22 pages, 6 figures. Updated version accepted for publication in ApJ. Full version of Table 2 may be found at http://www.astro.princeton.edu/~cblake/BlakeBloom/tab2.ps