Blue loops of intermediate mass stars - II. Metallicity and blue loops | |
Xu HY(许华崟)1![]() ![]() | |
刊名 | ASTRONOMY & ASTROPHYSICS
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2004-04 | |
卷号 | 418期号:1页码:225-233 |
关键词 | stars : evolution stars : interiors stars : Hertzsprung-Russell (HR) and C-M diagrams |
ISSN号 | 0004-6361 |
通讯作者 | Xu, HY (reprint author), Natl Astron Observ, Yunnan Observ, POB 110, Kunming 650011, Peoples R China. |
产权排序 | 第一完成单位 |
英文摘要 | Based oil the results of the blue loop formation for models of solar-like metallicity, we have explored the blue loop evolution of metal-poor stars. Three series of models with a wide ran.-c of metallicity and the initial helium abundance were calculated. An important parameter, eta(c), defined as the envelope convection mass divided by the total envelope mass at the bottom of the RGB. was introduced as a criterion to determine the formation of the blue loop. We have found that the low-Z models will develop extensive blue loops when eta(c) is lower than a critical value eta(crit). The physical explanation for this result Could be as follows. Lower Z reduces the envelope opacity and leads to a hotter stellar envelope and a bluer RGB. Thus file model will have a smaller eta(a) at the top and an even smaller eta(c) at the bottom of the RGB. When eta(c) is lower than the critical value eta(crit), the envelope is radiation-dominated. Under this condition and the constraint of the virial theorem, the response of the star to the increase of the stellar luminosity is to contract to increase the thermal conductivity coefficient in the stellar envelope and to form a blue loop. Compared with the high-Z models, we have confirmed that the development of convection in the stellar envelope is a crucial factor to determine the formation of the blue loop, but the low-Z models reach low eta(c) values in a different way from the high-Z models. in which the modulation of the nuclear reaction rates by higher N-14 abundance in the H-burning shell is responsible for the stars to get small eta(c) values. It has been found that eta(crit) depends not only on the stellar mass, but also on metallicity and the initial helium abundance. Our numerical results show that eta(crit) decreases with Z while slowly increases with Y. |
学科主题 | Astronomy & Astrophysics |
WOS标题词 | Science & Technology ; Physical Sciences |
类目[WOS] | Astronomy & Astrophysics |
研究领域[WOS] | Astronomy & Astrophysics |
关键词[WOS] | STELLAR MODELS ; EVOLUTION ; HELIUM ; OPACITIES ; ABUNDANCES ; SOLAR |
收录类别 | SCI ; EI |
原文出处 | http://www.aanda.org/articles/aa/abs/2004/16/aa3972/aa3972.html |
语种 | 英语 |
WOS记录号 | WOS:000221299500027 |
内容类型 | 期刊论文 |
源URL | [http://ir.ynao.ac.cn/handle/114a53/5173] ![]() |
专题 | 云南天文台_恒星物理研究组 |
作者单位 | 1.National Astronomical Observatories/Yunnan Observatory, PO Box 110, 650011 Kunming, PR China 2.Joint Laboratory for Optical Astronomy, Chinese Academy of Sciences, PR China |
推荐引用方式 GB/T 7714 | Xu HY,Li Y. Blue loops of intermediate mass stars - II. Metallicity and blue loops[J]. ASTRONOMY & ASTROPHYSICS,2004,418(1):225-233. |
APA | Xu HY,&Li Y.(2004).Blue loops of intermediate mass stars - II. Metallicity and blue loops.ASTRONOMY & ASTROPHYSICS,418(1),225-233. |
MLA | Xu HY,et al."Blue loops of intermediate mass stars - II. Metallicity and blue loops".ASTRONOMY & ASTROPHYSICS 418.1(2004):225-233. |
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