A CORRELATION BETWEEN THE INTRINSIC BRIGHTNESS AND AVERAGE DECAY RATE OF GAMMA-RAY BURST X-RAY AFTERGLOW LIGHT CURVES


RACUSIN J. L., OATES S. R., de Pasquale M., KOCEVSKI D.

ASTROPHYSICAL JOURNAL, vol.826, no.1, 2016 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 826 Issue: 1
  • Publication Date: 2016
  • Doi Number: 10.3847/0004-637x/826/1/45
  • Journal Name: ASTROPHYSICAL JOURNAL
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Istanbul University Affiliated: No

Abstract

We present a correlation between the average temporal decay (alpha(X,avg,> 200 s)) and early-time luminosity (L-X,L-200 (s)) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity-average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.