γ射线暴谱硬度比的时间演化特征

The Temporal Evolution of the Hardness Ratio of Gamma-Ray Bursts

采用小波分析方法对康普顿γ射线天文台(CGRO)上的BATSE仪器观测到的γ暴光变曲线数据进行去噪处理,并提出时间分辨的谱硬度比定义,用包含有599个暴的样本研究谱硬度比随时间的演化规律,结果表明:(1)样本中77%暴的谱硬度比随时间按"硬到软"规律演化,而23%暴谱硬度比随时间按"软到硬"规律演化,尤其是3%暴在整个暴中呈现单调的"软到硬"趋势。(2)平均谱硬度比随时间单调地以"硬到软"规律演化。(3)持续时间不同的暴,其谱硬度比演化曲线有较大的差异,其中"硬到软"演化趋势最显著的是持续时间在23～35s之间的那些暴;持续时间在1～10s的暴的演化特征跟其它组差异最显著,呈现比较明显的"软到硬"演化规律;持续时间在35～53s之间的暴平均谱硬度比几乎没有随时间演化。(4)不同辐射强度的暴平均谱硬度比的演化特征不同,随着峰值流量的增大,谱硬度比演化由"硬-软-硬"逐渐转变为"软-硬-软":峰值流量越大,"软-硬-软"的趋势越显著,而峰值流量越小,其峰值流量"硬-软-硬"的趋势越显著。我们对这些结果进行了简单的讨论。

The temporal evolution of hardness ratio (HR) of gammaray bursts (GRBs) have been studied with a sample of 599 bursts observed by the BATSE on board of the CGRO.A wavelet package denoising techniqie has been applied to substract noise from burst tempral profiles and a definition of time resolved hardness ratio has been proposed to investigate tempral evolutional features of the HR of GRBs.The results show that:(1) For most of the bursts in the sample (77%) the tempral evolutions of the HR are 'hard to soft',while a small fraction of bursts in the sample (23%) are 'soft to hard ',especial 3% of bursts in the sample are monotonous 'soft to hard'.(2) The temporal evolutional features of HRs in different groups of GRBs with different duration are quite different.Those bursts with duration between 23-35 sec. tend to have more obvious 'hard to soft' feature than others,and those bursts with duration between 1-10 second tend to have more clear 'soft to hard' feature than others.Those bursts with duration between 35-53 sec are almost constant.(3) The temporal evolutional features of HRs in different groups of GRBs with different peak fluxes are quite different too.For more intense bursts,the tempral evolutional features of the HR tend to be more 'soft to hard'.Based on the results,a brief discussion has been addressed.