B型热亚矮星模型的创建和星震学分析  

The construction and asteroseismological analysis of the model of hot sub-dwarf B star

作　　者：李云[1] 宋汉峰[1,2,3] 

机构地区：[1]贵州大学理学院物理系,贵州贵阳550025 [2]中国科学院天体结构与演化重点实验室,云南昆明650011 [3]中科院国家天文台-贵州大学天文联合研究中心,贵州贵阳550025

出　　处：《山东大学学报（理学版）》2013年第5期43-50,共8页Journal of Shandong University(Natural Science)

基　　金：贵州省教育厅自然科学研究项目(黔教科2010002);中国科学院天体结构与演化重点实验室开放课题资助项目(OP201107)

摘　　要：利用恒星结构演化程序将1.6M⊙左右的小质量星演化到红巨星顶点,在氦闪结束后经过大量的质量损失,使得恒星总质量约为0.5M⊙。此时恒星中心为一个开始燃烧的氦核,外部为稀薄的氢壳层(氢壳层的质量Menv≤0.02M⊙),称为初始B型热亚矮星模型(B-type hot sub-dwarf star,简称sdB星)。对于不同质量和氢壳层的初始sdB星模型,表面有效温度和重力加速度都不同,但都分布在零龄极端水平分支与终止极端水平分支之间,并且它们的演化轨迹相似。本文由sdB星的理论演化模型得到了它的内部结构参量,并进行星震学分析。结果发现随着恒星的演化,表面有效温度较高时检测到有p模式(p-modes)震动,较低时检测到有g模式(g-modes)震动,在这两个区域之间,两种模式共存。p-modes包括径向震动(l=0)和非径向震动(l=1～5),周期为80～600 s。只有非径向低球谐度(l=1～5)的g-modes,周期为1 800～9 000 s。将热亚矮星的结构参数代入绝热线性震动程序中,得到Brunt-Visl频率、Lamb频率、本征频率、惯性参数等,并研究了sdB星的震动特性。A low mass star（about 1.6 M⊙） can evolve to the tip of the RGB phase through the stellar evolution code（MESA code）.After igniting the helium flash,the stars lose a lot of mass and remain a total mass around 0.5M⊙.The star has a central helium burning core and has a tiny（≤0.02M⊙） hydrogen-rich envelope.It is called as the zero age B-type sub-dwarf star model.For different total mass and different hydrogen-rich envelope,these models have different effective temperature and gravity.They distribute with small range from the zero age extreme horizontal branch to the termination age extreme horizontal branch.Their evolutionary track is very similar.The internal structure can be derived from the theoretical evolutionary model.It is found that p-mod appears in the models with high effective temperature whereasg-mod appears in the models with low effective temperature.Both of them can exist between the high temperature and the low temperature.Radial（l=0）and nonradial（from l=1 up to l=5）oscillation modes of p-mod have the periods of 60-500s and nonradial oscillation modes of g-mod has the periods of 1800-5000s.Some pulsation quantities,such as Brunt-Visl frequency,Lamb frequency,eigenfrequency and inertial parameter can be investigated when the adiabatic linearity pulsation code can be used.The characters of the pulsation for the sdb star have been investigated.

关 键 词：B型热亚矮星 演化 恒星结构 脉动 p模式震动 g模式震动 

分 类 号：P145.4[天文地球—天体物理]