An analysis of the durations of Swift gamma-ray bursts
Abstract
Context: Swift detectors are found to be more sensitive to long-soft bursts than pre-Swift missions. This may largely bias the distribution of durations and thus classification of gamma-ray bursts.
Aims: We systematically investigate the duration distribution of gamma-ray bursts in the Swift era vs. that of pre-Swift bursts.
Methods: For the purpose of this study, statistical methods such as the K-S test and linear/non-linear fitting analysis have been used to examine the duration properties of Swift bursts in both observer and source frames.
Results: For 95 GRBs with known redshift, we show that two log-normal distributions of duration are clearly divided at T90≃2 s. The intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value and the distribution exhibits a narrower width than the observed one. Swift long bursts exhibit a wider duration dynamic range in both observer and source frames in comparison to pre-Swift long bursts.
Conclusions: We find that Swift bursts and pre-Swift ones can share the same criterion of classification in terms of duration at 2 s, although both monitors have large differences with respect to sensitivity of a given energy band.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2008
- DOI:
- 10.1051/0004-6361:20079210
- arXiv:
- arXiv:0708.4049
- Bibcode:
- 2008A&A...484..293Z
- Keywords:
-
- gamma rays: bursts;
- gamma rays: theory;
- Astrophysics
- E-Print:
- 5 pages, 4 figures and 2 table