The correlations between hardness ratios and fitting parameters in GRB spectrum |
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| Authors: | En-Wei Liang Guang-Zhong Xie Xiao-Ge Rong |
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| Institution: | (1) Yunnan Observatory, Chinese Academy of Sciences, Kunming, Yunnan, 650011, P. R. China;(2) National Astronomical Observatories, Chinese Academy of Sciences, P. R. China;(3) Physics Department, Guangxi University, Nanning, Guangxi, 530004, P. R. China;(4) Department of Physics, Guangxi Normal University, Guilin, Guangxi, 541004, P. R. China |
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| Abstract: | In this paper, besides general definition of hardness ratio of gamma-ray bursts (GRBs), HR
32, we also presented new definitions of hardness ratios, HR
hl and HR
ll, then presented the results of correlation studies, examining the association between the hardness ratios and the spectral
fitting parameters (E
0 or E
peak, α, β) by using the GRB data observed by BATSE. The HR
hl is defined as the fluence of channel 4 divided by the sum of the fluences of channels 1 to 3,and the HR
ll is defined as the fluence of channel 3 divided by the sum of the fluences of channel 1 and 2. We found that E
0 and E
peak are correlated with hardness ratios, and β is only correlated with log (HR
hl). The α is not correlated with any hardness ratios in the total sample of GRBs, while it correlated with log (HR
ll) and log (HR
32) in the two subsets seperated at log (HR
ll) = 0.34 ×α +0.66, respectively. These results show that a harder spectra tends to be steeper and has a higher E
peak or E
0; HR
hl describes the spectral behaviors in high energy, while both of HR
ll and HR
32 reflect the spectral characteristics in low energy; the spectral behaviors in low energy are different for the two subsets.
We also presented a brief qualitative analysis discussion to the correlations and suggested that the correlations are caused
by both of intrinsic and cosmological effects, but intrinsic effects are dominant.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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