粘滞对黑洞吸积盘的截断的影响  

The Influence of Viscosity on the Truncation of Accretion Disk Around Black Holes

作　　者：牛强[1] 

机构地区：[1]中国科学院国家天文台/云南天文台,昆明650011

出　　处：《天文学报》2008年第3期243-250,共8页Acta Astronomica Sinica

摘　　要：采用吸积盘-冕模型研究了粘滞对黑洞X射线双星和低光度活动星系核(LLAGN)中吸积盘的截断以及黑洞X射线双星中高低态转变的影响.以前的分析表明,冕的结构对粘滞的大小非常敏感.因此详细计算了一系列粘滞系数情况下冕的结构.为了便于与观测比较,将数值计算结果进行解析拟合得到最大蒸发率和粘滞系数α的关系,M/M_(EDD)≈1.08α^(3.35);截断半径和粘滞系数的关系,R/R_s≈36.11α^(-1.94)这些结果可以用来解释光谱态的高低态的转换和截断半径的变化.并将这些结果应用到几个黑洞X射线双星XTE J1118 +480,GX 339—4,以及活动星系核NGC 4636中.The disk corona evaporation model(Meyer et al.2000;Liu et al.2002) has been established to explain the spectral state transition and disk truncation in black hole X- ray transients and supermassive black holes.Simple estimation(Meyer et al.2000)and nu- merical calculation(Meyer et al.2001)show that the transition luminosity is strongly depend- ent on the viscous parameterα,so is the truncation radius at low/hard state of accreting black holes.This paper studies study in detail the influence of viscous parameter on the maximal e- vaporation rate and the corresponding radius,and hence the influence on the spectral state transition and disk truncation.On the basis of numerical calculations for a number of viscous parameter values,It is shown how the transition rate and truncation radius analytically vary with viscous parameterαby fitting the numerical data. In section 2,a simple description of disk corona model(Meyer et al.2000)is giv- en.In section 3 the detailed numerical results are present.Assuming a typical AGN black hole of 108 solar mass,the coronal structure for a series of viscous coefficients is calculated.The numerical data are fitted into analytical forms for the relation between the maximal mass evaporation rate and viscosityα,M/M_(EDD)≈1.08α^(3.35),and for the re- lation between the truncation radius and the viscosity,R/R_5≈36.11α^(-1.94).The results are also shown in Figs.2a and 2b.These results demonstrate that the viscosity of the corona gas strongly affects the truncation radius of an accretion disk and the spectral transition.For comparison,the results for a 10 solar mass black hole are given.The in- fluence of viscosity on the evaporation rate and disk truncation are the same as that for supermassive black holes.This confirms previous work that the evaporation rate(in Eddington accretion rate)and the truncation radius(in Schwarzschild radius unit)are independent on the mass of the central black hole. In Section 4 our theoretical results to are applied some X-ray transients and AGN. Assum

关 键 词：物理数据与过程 黑洞物理 吸积 吸积盘 X-射线 双星 

分 类 号：P145[天文地球—天体物理]