Structure and evolution of low-mass W Ursae Majoris type systems - III. The effects of the spins of the stars

	Structure and evolution of low-mass W Ursae Majoris type systems - III. The effects of the spins of the stars
	Li LF(李立芳); Han ZW(韩占文); Zhang FH(张奉辉)
刊名	MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
	2005-06-11
卷号	360 期号:1 页码:272-281
关键词	stars : activity binaries : close stars : evolution stars : rotation
ISSN号	0035-8711
通讯作者	Li, LF (reprint author), Chinese Acad Sci, Yunnan Observ, Natl Astron Observ, POB 110, Kunming 650011, Yunnan Province, Peoples R China.
产权排序	第一完成单位
英文摘要	In a previous paper, using Eggleton's stellar evolution code, we have discussed the structure and evolution of low-mass W Ursae Majoris (W UMa) type contact binaries with angular momentum loss owing to gravitational radiation or magnetic braking. We find that gravitational radiation is almost insignificant for cyclic evolution of low-mass W UMa type systems, and it is possible for angular momentum to be lost from W UMa systems in a magnetic stellar wind. The weaker magnetic activity shown by observations in W UMa systems is likely caused by the lower mass of the convective envelopes in these systems than in similar but non-contact binaries. The spin angular momentum cannot be neglected at any time for W UMa type systems, especially for those with extreme mass ratios. The spin angular momenta of both components are included in this paper and they are found to have a significant influence on the cyclic evolution of W UMa systems. We investigate the influence of the energy transfer on the common convective envelopes of both components in detail. We find that the mass of the convective envelope of the primary in contact evolution is slightly more than that in poor thermal contact evolution, and that the mass of the convective envelope of the secondary in contact evolution is much less than that in poor thermal contact evolution. Meanwhile, the rate of angular momentum loss of W UMa type systems is much lower than that of poor thermal contact systems. This is indeed caused by the lower masses of the convective envelopes of the components in W UMa type systems. Although the models with angular momentum loss for W UMa systems exhibit cyclic evolution, they seem to show that a W UMa system cannot continue this type of cyclic evolution indefinitely, and it might coalesce into a fast-rotating star after about 1200 cycles of evolution (about 7.0 x 10(9) yr).
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]	ANGULAR-MOMENTUM LOSS ; CLOSE BINARY-SYSTEMS ; CONTACT BINARIES ; STELLAR EVOLUTION ; CLUSTER ; LIMIT
收录类别	SCI
原文出处	http://mnras.oxfordjournals.org/content/360/1/272
语种	英语
WOS记录号	WOS:000229908100024
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/4414]
专题	云南天文台_大样本恒星演化研究组
作者单位	National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, Kunming, Yunnan Province 650011, China
推荐引用方式 GB/T 7714	Li LF,Han ZW,Zhang FH. Structure and evolution of low-mass W Ursae Majoris type systems - III. The effects of the spins of the stars[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2005,360(1):272-281.
APA	Li LF,Han ZW,&Zhang FH.(2005).Structure and evolution of low-mass W Ursae Majoris type systems - III. The effects of the spins of the stars.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,360(1),272-281.
MLA	Li LF,et al."Structure and evolution of low-mass W Ursae Majoris type systems - III. The effects of the spins of the stars".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 360.1(2005):272-281.