EGRET伽马射线源光变的数值分析  

Numerical Analysis of Variability Indices of EGRET Gamma-Ray Sources

作　　者：韩朝霞[1] 张力[2,3] 申雁鸣[4] 

机构地区：[1]河南科技大学理学院 [2]中国科学院国家天文台/云南天文台 [3]云南大学物理系 [4]中国科学院上海光学精密机械研究所

出　　处：《南京大学学报（自然科学版）》2007年第1期19-28,共10页Journal of Nanjing University（Natural Science）

基　　金：河南科技大学人才科学研究基金(05-033)

摘　　要：高能γ射线天文是当今天体物理学中重要的研究领域之一,康普顿γ射线天文台的高能γ射线望远镜(EGRET)提供了大量的观测数据,发现了271颗高能γ射线点源,其中170颗未被证认.目前的研究表明,一些未证认源可能是活动星系核,银盘附近的一些未证认源可能与脉冲星和超新星遗迹(SNRs)有联系.也发现几个未证认源可能是星系扩散发射所造成的伪造源.但就像大家所讨论的那样,未证认源的数目比所期望的更多.这些未证认高能γ射线点源的基本物理特性是什么呢?以此为动机,利用不同的光变分析方法,对这些未证认源进行了仔细的统计分析.目前,共有3种光变分析方法用来研究γ射线源的γ射线光变,它们分别是V指数方法、I指数方法和τ指数方法.通过数值计算EGRET源的I值和V值,发现这两种光变方法在统计上是一致的.把计算结果与Tompkins(1999)所计算的τ值进行比较,发现如果观测数据足够精确,这3种方法在统计上也是一致的.联合这3种光变分析方法,分析了30个与脉冲星位置一致的EGRET点源的光变以及40个低纬度持续稳定未证认源的光变.结果表明30个与脉冲星位置一致的EGRET点源中有14个与脉冲星有本质的或很可能的联系,40个低纬度持续稳定未证认源中有16个是可能的脉冲星候选源.High-energy γ-ray astronomy is one of important research fields in current astrophysics. EGRET boarded on Compton Gamma Ray Observatory （CGRO） provided more observed data and discovered 271 high-energy γ-ray point sources, 170 of which have not been identified yet. The present researches indicate that some unidentified γ-ray sources may be AGNs, and some unidentified sources in the Galactic plane （｜b｜〈5°） may correlate with pulsar and supernova remnants（SNRs）. Several unidentified sources are also found to be fabricated sources because of galaxy diffusion emission. But, the number of unidentified γ-ray sources is larger than that of expected ones. In order to understand the basic physics of the unidentified γ-ray point sources, we studied statistically them using different variability methods. Presently, three variability methods were used to study γ-ray variability of the γ-ray sources. They included the methods of V-index, I-index and τ-index. We calculated the I-values and V-values for EGRET sources, and found that these two indices should have statistical consistency. We compared the results with τ-values given by Tompkins （1999）, and found that the three methods were also statistically identical if the observations are enough accurate. We combined these three methods to analyze the variability of 30 EGRET point sources which are positionally consistent with pulsars and the variability of 40 persistent unidentified sources at low latitude. It is found that 14 of the 30 point sources may be associated with pulsars, and 16 of the 40 persistent unidentified sources are possible pulsar candidates.

关 键 词：Γ射线 观测 光变 数值分析 

分 类 号：P172.3[天文地球—天文学]