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A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light CurvesWe present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,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 â€" 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.
Document ID
Document Type
Reprint (Version printed in journal)
Racusin, J. L.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Oates, S. R.
(Instituto de Astrofisica de Andalucia Granada, Spain)
De Pasquale, M.
(Mullard Space Science Lab. Dorking, United Kingdom)
Kocevski, D.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
November 14, 2017
Publication Date
July 18, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 826
Issue: 1
ISSN: 0004-637X
Subject Category
Report/Patent Number
Funding Number(s)
OTHER: 661032
Distribution Limits
gamma-ray burst: general X-rays: burst
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