Astronomy and Astrophysics – Astrophysics – High Energy Astrophysical Phenomena
Scientific paper
2009-02-20
Astrophys.J.707:328-342,2009
Astronomy and Astrophysics
Astrophysics
High Energy Astrophysical Phenomena
34 pages, including 2 tables and 9 figures. Accepted for publications in ApJ. This is the forth paper of a series. Paper I, II
Scientific paper
10.1088/0004-637X/707/1/328
By analyzing the Swift/XRT lightcurves detected before 2009 July, we find 19 cases that monotonously decay as a single power law (SPL) with an index of 1 ~ 1.7 from tens (or hundreds) to ~ 10^5 seconds post the GRB trigger, apparently different from the canonical lightcurves characterized by a shallow-to-normal decay transition. No statistical difference is found in their prompt gamma-rays, and the X-ray properties of the two samples are also similar, although the SPL sample tend to have a slightly lower NH value of the host galaxies and larger energy release compared with the canonical sample. The SPL XRT lightcurves in the burst frame gradually merge into a conflux.The normal decay segment for the canonical sample has the same feature. Similar to the normal decay segment, the SPL lightcurves satisfy the closure relations of external shock models. If the X-rays are the afterglow of the GRB fireball, our results indicate that the shallow decay would be due to energy injection and the total energy budget after injection for both samples of GRBs is comparable. More intriguing, we find that a prior X-ray emission model proposed by Yamazaki is more straightforward to interpret the data. We show that the zero times (T0) of the X-rays atisfy a log-normal distribution, and the negligible T0's of the SPL sample are consistent with being the tail of T0 distributions at low end. Referenced to T0, the canonical XRT lightcurves well trace the SPL lightcurves. The T0's of the canonical lightcurves in our analysis are usually much larger than the offsets of the known precursors from the main GRBs, indicating the X-rays would be an emission component from external shocks prior to GRB trigger. The lack of detection of a jet-like break in most XRT lightcurves implies that the opening angle of its jet would be usually large.
Hou Shu-Jin
Liang E.-W.
LV Hou-Jun
Zhang Bin-Bin
Zhang Bing
No associations
LandOfFree
A Comprehensive Analysis of Swift/XRT Data: IV. Single Power-Law Decaying Lightcurves vs. Canonical Lightcurves and Implications for a Unified Origin of X-rays does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Comprehensive Analysis of Swift/XRT Data: IV. Single Power-Law Decaying Lightcurves vs. Canonical Lightcurves and Implications for a Unified Origin of X-rays, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Comprehensive Analysis of Swift/XRT Data: IV. Single Power-Law Decaying Lightcurves vs. Canonical Lightcurves and Implications for a Unified Origin of X-rays will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-670413