Properties of time profiles of gamma-ray bursts using pulse decomposition analysis
The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. This pulse decomposition analysis has previously been performed on a small sample of bright long bursts using binned data from BATSE, which comes in several data types, and on a sample of short bursts using the BATSE Time-Tagged Event (TTE) data type. The author has developed an interactive pulse-fitting program written in IDL using the phenomenological pulse model of Norris, et al., a maximum-likelihood fitting routine, and a semi-automatic routine to determine initial guesses for the fitting routine from time profiles smoothed by a wavelet de-noising algorithm. The author has used this program to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. He presents statistical information on the attributes of pulses comprising these bursts, including relations between pulse characteristics in different energy channels, and the evolution of pulse characteristics through the course of a burst. He carries out simulations to determine the biases that his procedures may introduce. Among the results are that pulses tend to have shorter rise times than decay times, and tend to be narrower and peak earlier at higher energies. He also examines correlations between brightness measures and timescale measures which may result from cosmological time dilation of bursts, or from intrinsic properties of burst sources or from selection effects. The correlations between these parameters among pulses within individual bursts give a measure of the intrinsic effects while the correlations among bursts could result both from intrinsic and cosmological effects. He finds that timescales tend to be shorter in bursts with higher peak fluxes, but tend to be longer in bursts with higher total fluences. He also finds that peak fluxes and total fluences of bursts are uncorrelated, indicating that they cannot both be good distance indicators for bursts.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 753307
- Report Number(s):
- SLAC-R-553; TRN: AH200009%%110
- Resource Relation:
- Other Information: PBD: 22 Feb 2000
- Country of Publication:
- United States
- Language:
- English
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