Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts
Abstract
We report evidence that the asymptotic low-energy power law slope alpha (below the spectral break) of BATSE gamma-ray burst photon spectra evolves with time rather than remaining constant. We find a high degree of positive correlation exists between the time-resolved spectral break energy E_pk and alpha. In samples of 18 "hard-to-soft" and 12 "tracking" pulses, evolution of alpha was found to correlate with that of the spectral break energy E_pk at the 99.7% and 98% confidence levels respectively. We also find that in the flux rise phase of "hard-to-soft" pulses, the mean value of alpha is often positive and in some bursts the maximum value of alpha is consistent with a value > +1. BATSE burst 3B 910927, for example, has a alpha_max equal to 1.6 +/- 0.3. These findings challenge GRB spectral models in which alpha must be negative of remain constant.
Keywords
Cite
@article{arxiv.astro-ph/9612118,
title = {Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts},
author = {A. Crider and E. P. Liang and I. A. Smith and R. D. Preece and M. S. Briggs and G. N. Pendleton and W. S. Paciesas and D. L. Band and J. L. Matteson},
journal= {arXiv preprint arXiv:astro-ph/9612118},
year = {2007}
}
Comments
12 pages (including 6 figures), accepted to ApJ