Methods and results of an automatic analysis of a complete sample of<i>Swift</i>-XRT observations of GRBs

TLDR

The authors provide a homogeneous X‑ray analysis of all 318 GRBs observed by Swift‑XRT up to July 2008, the largest such sample published to date. They employ an automated pipeline developed by the Swift‑XRT team to generate enhanced positions, light curves, hardness ratios, spectra, and offer web tools for users to produce these products for any XRT‑observed object. The analysis reveals a consistent underlying behavior that can produce diverse light‑curve morphologies, yet reconciling the data with external forward‑shock models requires prolonged energy injection over days to weeks.

Abstract

We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2–3, we detail the methods which the Swift-XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift-XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4–6, we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light-curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks.