潮汐转矩对转动恒星结构和演化的影响研究  

The effect of tidal torques on the structure and evolution of rotating stars

作　　者：宋汉峰[1,2,3] 王江涛[1] 

机构地区：[1]贵州大学理学院,贵阳550025 [2]瑞士日内瓦大学天文系 [3]中国科学院天体结构与演化重点实验室,昆明650011

出　　处：《中国科学：物理学、力学、天文学》2016年第11期90-98,共9页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11463002);中国科学院天体结构与演化重点实验室开放课题(编号:OP201405);国家公派留学西部访学项目基金(编号:留金法[2015]5103)资助

摘　　要：潮汐效应是影响恒星结构和演化非常重要的物理因素.本文研究了影响潮汐转矩系数E_2的三个理论模型.根据转动恒星中的角动量传输和元素扩散方程,给出了潮汐转矩系数E_2对转动恒星内部结构和元素混合的影响.结果表明:潮汐转矩系数E_2与恒星质量、金属丰度、演化时间有密切关系.潮汐转矩系数E_2越大,双星系统轨道角动量转化为子星自转角动量和自转角动量在恒星内部传输的效率越高.强潮汐转矩造成恒星表面有较大的氦和氮元素的超丰和对流核质量,使恒星具有较高的光度.然而,对比模型M1和M3,充分的转动混合效应可以降低元素的不透明度和辐射温度梯度,压制转动动力学效应造成的辐射温度梯度的增加,使恒星中心对流核减少.强潮汐产生的转动混合效应使氢元素丰度和数密度增加,增强氢燃烧效率,提高中心核温度,使恒星膨胀,具有较大的转动惯量.因此,研究潮汐效应对元素混合效应的影响,对密近双星的演化具有重要意义.The tide is a very important physical factor which can affect significantly the structure and evolution of stars. Tidal coefficients in three theoretical models have been explored in this paper. Basing on the equations of angular momentum transport and chemical elements mixing, we can investigate the effect of tidal coefficients on the structure and mixing of chemical elements. It is shown that the tidal coefficient is related to stellar masses, metal abundances, and evolutionary stages. The tidal coefficient E2 increases with stellar mass but decreases metal abundance and evolutionary time. The bigger tidal coefficient is, the higher efficiency of processes which the orbital angular momentum transforms into the spin angular momentum will be. Furthermore, angular momentum transports efficiently inside the star. Tidal torques can enhance the helium and nitrogen at the stellar surface and enlarge the convective core which can cause the star to shift toward high luminosity. Comparing model M1 with M3, we find that rotational mixing induced by tidal torque can reduce the opacity, and radiative temperature gradient but it can inhibit the hydrodynamic effects of centrifugal force which can increase the radiative temperature gradient. Therefore, tidally induced rotational mixing can decrease the convective core. Furthermore, rotational mixing induced by tidal torque can increase both the number density of hydrogen in stellar core and the efficiency of nuclear reactions. This physical process may increase central temperatures and cause the star to expand greatly. The star will have a large moment of inertia. It is of significance to investigate the tidal mixing in close binary systems.

关 键 词：恒星结构与演化 转动 潮汐 

分 类 号：P152[天文地球—天文学]