• 中文核心期刊要目总览
  • 中国科技核心期刊
  • 中国科学引文数据库(CSCD)
  • 中国科技论文与引文数据库(CSTPCD)
  • 中国学术期刊文摘数据库(CSAD)
  • 中国学术期刊(网络版)(CNKI)
  • 中文科技期刊数据库
  • 万方数据知识服务平台
  • 中国超星期刊域出版平台
  • 国家科技学术期刊开放平台
  • 荷兰文摘与引文数据库(SCOPUS)
  • 日本科学技术振兴机构数据库(JST)

AGB星的超星风与热脉动的研究

The Mechanism Investigation on the Superwind and Thermal Pulse in the AGB Star

  • 摘要: 至今国际上对AGB星的超星风、热脉动及振动的理论研究工作中都忽略了湍流压的存在, 然而对于一个整个外壳都处于完全对流的AGB星, 湍流压是存在的, 并且由于湍流压的存在将对气体压强、密度、温度以及各热力学量产生影响, 因而对AGB星的超星风、热脉动及振动产生影响。本文以恒星结构演化理论中常用的混合程对流理论为基础, 给出了湍流压以及考虑湍流压情况下恒星内部物态方程和各热力学量的表达式, 并给出了判别恒星外壳产生动力学非稳定性的判据, 并在此基础上研究了质量为2.8M⊙和7M⊙的恒星从主序到AGB星的演化。目的是研究有湍流压情况下AGB星的超星风及热脉动的机理。结果表明, 对于7M⊙恒星, 在红巨星及AGB阶段, 湍流压可以达到总压强的30%,并且对恒星的结构产生重要影响, 对于2.8M⊙恒星, 在红巨星及AGB阶段影响较小。由于湍流压的作用, 2.8M⊙和7M⊙恒星在AGB阶段和红巨星阶段, 靠近表面的区域会出现动力学非稳定性, 造成物质向外喷流, 这就是AGB星和红巨星产生强大星风的物质损失的原因。研究还表明, 湍流压效应造成7M⊙AGB星的氢燃烧壳层产生主周期为50年的脉动现象, 同时使氦燃烧壳层的热脉动提前发生和周期变短。

     

    Abstract: The theoretical investigations on the superwind and thermal pulsation in the AGB star so far are based on the neglecting theturbulent pressure. How ever, for an AGB star with complete convectiv eenv elope the turbulent pressure exists and has important influence on the gaspressure, density, tempera ture and the ther modynamical quanti ties. Therefore, the existence of the turbulent perssure must influence on the superwind and thermal pulse in the AGB star. In this thesis we have derived the expressions of the turbulent pressure, the state equation and the thermody namical quanti ties based on the mixing lengh covection theory and given a criterion for the occurrence of the dy namical instability in the convective envelope. In order to investiga te the effects of turbulent pressure on the superwind and thermal pulse in the AGB star, the evolution of the stars with mass of 2.8M⊙ and 7M⊙ from the main sequence to the AGB stage has calculated respectively. The results show that the turbulent pressure can be 30 percent of the total pressure in the regions closed to the surface of an AGB star with 7M⊙and has an important influence on the innerst ructure and evolution. Owing to the effect of turbulent pressure the regions closed to the surface of AGB star and redgiant star are insta bledynamically. This causes an outwards mass ejection which forms the superwind in the AGB star or the strong stellar wind in the red giant star. Due to the effect of the turbulent pressure, the thermal pulse in the He-burning shell occurs early and its period becomes shorter.

     

/

返回文章
返回