Are the missing X-ray breaks in Gamma-ray Burst afterglow light curves merely hidden?

Abstract

Gamma-ray burst afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX, or pre-Swift era. Specifically, relatively few breaks, consistent with jet breaks, are observed in the X-ray light curves of these bursts. If these breaks are truly missing, it has serious consequences for the interpretation of GRB jet collimation and energy requirements, and the use of GRBs as cosmological tools. Here we address the issue of X-ray breaks that are possibly `hidden' and hence the light curves are misinterpreted as being single power laws. We do so by synthesising XRT light curves and fitting both single and broken power laws, and comparing the relative goodness of each fit via Monte Carlo analysis. Even with the well sampled light curves of the Swift era, these breaks may be left misidentified, hence caution is required when making definite statements on the absence of achromatic breaks.

6 pages including 3 figures, accepted to MNRAS after revisions

References in corpus (5)

• An online repository of Swift/XRT light curves of GRBs
• Gamma-Ray Bursts: Progress, Problems & Prospects
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
• Gamma-Ray Burst Afterglows as Probes of Environment and Blastwave Physics II: the Distribution of p and Structure of the Circumburst Medium
• GRB 060206 and the quandary of achromatic breaks in afterglow light curves

Cited by in corpus (2)

• Multiwavelength analysis of the intriguing GRB 061126: the reverse shock scenario and magnetization
• The complex light-curve of the afterglow of GRB071010A