Gamma暴光变曲线主峰特征参量的分布

Distributions of the Characteristics of the Most Intense Pulses in Gamma-Ray Burst Light Curves

γ暴被认为由一系列脉冲所组成,其光变曲线中的峰对应着脉冲爆发过程,主峰对应着最强烈的脉冲爆发过程,所受背景噪音的污染相对来说最小.因此光变曲线的主峰最适合于用以研究脉冲特性.本文对康普顿γ射线天文台观测卫星上BATSE仪器观测到的γ暴的光变曲线的主峰数据进行统计分析,以研究gamma暴中脉冲的持续时间、振幅、对称因子(δ,上升时标比下降时标)、窄度因子(η,半宽度比持续时间)等特征参量的分布特征.我们发现:(1)脉冲的持续时间主要在0.1s～0.2s之间,第1和第4能道的持续时间略短,尤其是第4能道.(2)1～4道振幅分布差异比较大,虽然众数都大约在600个计数/s附近,但中值差异很大,1～4道中值比为:0.44:0.59:1.00:0.32.(3)1～4道脉冲的形状都是不对称的,峰的形状差异不是很大,1、2、3道间差异最小,4道略尖锐.两个主要形状参数δ和η在不同能道间的差异不大.1～4道的δ值最可几值一般在0.75～0.85间.η在0.55～0.58间,平均值为0.52±0.10.

It is believed that the light curves of gamma-ray bursts (GRBs) are composed of a series of pulses. The light curves of most intense pulse, which correspond to the most violent outburst in a burst, might have the best ratio of signal-to-noise. Thus, they are the best candidates to study the characteristics of the pulses. In this work, we present the results of a statistical analysis to the distributions of the characteristics of the most intense pulses in GRBs detected by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO). These characteristics include pulse duration, amplitude, symmetry factor (δ, ratio of rising time to decaying time in a pulse),narrowness factor (η,FWHM to pulse duration). Our results show that the pulse durations range in 0.1-0.2 seconds with slight shorter in channels 1 and 4 (especial channel 4) than that in other channels. The distribution of pulse amplitudes is very scatter with a mode of 600 photons per second in four channels and a relative median of 0.44:0.59:1.00:0.32. The shapes of the pulses are asymmetric with a slight difference in channels 1, 2, 3 . The distributions of δ and η in different channels are almost the same, which are clustered at 0.75 -0.85 and 0.55-0.58 (the mean is 0.52±0.10) forδ and η, respectively.