Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars

doi:10.1088/1674-4527/11/11/010

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	Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars
	Lai XJ(赖祥军)1,2,3 ; Li Y(李焱)1,2 ; Lai, XJ (reprint author), Chinese Acad Sci, Yunnan Observ, Natl Astron Observ, Kunming 650011, Peoples R China.
发表期刊	RESEARCH IN ASTRONOMY AND ASTROPHYSICS
	2011-11
卷号	11 期号:11 页码:1351-1370
DOI	10.1088/1674-4527/11/11/010
产权排序	第1完成单位
收录类别	SCI
关键词	Stars: Convection Stars: Interiors Stars: Hr Diagram-blue Loops-cepheids Galactic Open Clusters
摘要	Based on the turbulent convection model (TCM), we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediate-mass stars, focusing on its influence on the formation and extension of blue loops in the Hertzsprung-Russell (HR) diagram. A diffusive mixing model is adopted during the Red Giant Branch (RGB) phase. The properties of the blue loop are changed by modification of the element profiles above the H-burning shell, which results from the incomplete mixing in the bottom overshooting region when the stellar model evolves up along the RGB. Such modification of the element profiles will lead to an increase of opacity in the region just above the H-burning shell and a decrease of opacity in the outer homogeneous convection zone, which will result in a quick decrease of the H-shell nuclear luminosity L-H when the stellar model evolves from the RGB tip to its bottom and, finally, a much weaker and smaller convection zone will be obtained in the stellar envelope. This helps to form a longer blue loop. The extension of the blue loop is very sensitive to the parameters (C-X and alpha(TCM)) of the diffusive mixing model and of the TCM. The results mainly show that: 1) comparing the results of the classical model with the mixing-length theory, the lengths of the obtained blue loops with different combinations of the values of C-X and alpha(TCM) are all increased and the length of the blue loop increases with the values of parameters C-X and alpha(TCM); 2) the diffusive mixing model can significantly extend the time of stellar models lingering on the blue side of the HR diagram, even though the length of the blue loop for the 7M(circle dot) star has a less prominent difference between the classical and diffusive mixing model; 3) both the observations referring to the location of the Cepheid instability strip and the number ratio N-B/N-R of blue to red evolved stars in the Galactic open clusters can confine the two parameters in a range of 0.5 <= alpha(TCM) <= 0.9 and 10(-5) <= C-X <= 10(-4) for the model of 5M(circle dot). However, for the case of the 7M(circle dot) star, there seems to be no such definite range to even only account for the observed number ratio N-B/N-R. In any case, our results based on the diffusive mixing model are on the whole in accordance with not only other theoretical ones but also the observations.
项目资助者	National Natural Science Foundation of China [10973035, 10673030]
语种	英语
学科领域	Astronomy & Astrophysics
文章类型	Article
ISSN	1674-4527
URL	查看原文
归档日期	2011-12-16
WOS记录号	WOS:000297441300010
WOS研究方向	Astronomy & Astrophysics
WOS类目	Astronomy & Astrophysics
关键词[WOS]	INTERMEDIATE-MASS STARS ; RED SUPERGIANT RATIO ; BLUE-TO-RED ; STELLAR EVOLUTION ; CLASSICAL CEPHEIDS ; AGB STARS ; ASTROPHYSICAL APPLICATIONS ; DYNAMICAL EVOLUTION ; OBSERVATIONAL TESTS ; INSTABILITY STRIP
引用统计	被引频次：8[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.ynao.ac.cn/handle/114a53/5205
专题	恒星物理研究组中国科学院天体结构与演化重点实验室
通讯作者	Lai, XJ (reprint author), Chinese Acad Sci, Yunnan Observ, Natl Astron Observ, Kunming 650011, Peoples R China.
作者单位	1.National Astronomical Observatories / Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China 2.Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China 3.Graduate University of Chinese Academy of Sciences, Beijing 100049, China
第一作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	Lai XJ,Li Y,Lai, XJ . Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars[J]. RESEARCH IN ASTRONOMY AND ASTROPHYSICS,2011,11(11):1351-1370.
APA	Lai XJ,Li Y,&Lai, XJ .(2011).Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars.RESEARCH IN ASTRONOMY AND ASTROPHYSICS,11(11),1351-1370.
MLA	Lai XJ,et al."Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars".RESEARCH IN ASTRONOMY AND ASTROPHYSICS 11.11(2011):1351-1370.

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