Journal Article

Hardness as a spectral peak estimator for gamma-ray bursts

A. Shahmoradi and R. J. Nemiroff

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 4, pages 2075-2090
Published in print October 2010 | ISSN: 0035-8711
Published online September 2010 | e-ISSN: 1365-2966 | DOI:
Hardness as a spectral peak estimator for gamma-ray bursts

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Simple hardness ratios are found to be a good estimator for the spectral peak energy in gamma-ray bursts (GRBs). Specifically, a high correlation strength is found between the νFν peak in the spectrum of Burst and Transient Source Experiment (BATSE) GRBs, Ep,obs and the hardness of GRBs, , as defined by the fluences in channels 3 and 4, divided by the combined fluences in channels 1 and 2 of the BATSE Large Area Detectors (LADs). The correlation is independent of the type of the burst, whether long-duration GRB (LGRB) or short-duration (SGRB) and remains almost linear over the wide range of the BATSE energy window (20–2000 KeV). Based on Bayes theorem and Markov Chain Monte Carlo techniques, we also present multivariate analyses of the observational data while accounting for data truncation and sample incompleteness. Prediction intervals for the proposed relation are derived. Results and further simulations are used to compute Ep,obs estimates for nearly the entire BATSE catalogue: 2130 GRBs. Based on these estimates, we also obtain for the first time the asymptotic Ep,obs distribution of GRBs detectable by BATSE. The observed Ep,obs distribution is well fit by the sum of two Gaussians, possibly representing the Ep,obs distribution of BATSE LGRBs and SGRBs peaking at 140 and 520 KeV, respectively. These results may be useful for investigating the cosmological utility of the spectral peak energy in GRBs intrinsic luminosity estimates.

Keywords: gamma-ray burst: general

Journal Article.  11121 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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