Structure and evolution of low-mass W Ursae Majoris type systems - II. With angular momentum loss

	Structure and evolution of low-mass W Ursae Majoris type systems - II. With angular momentum loss
	Li LF(李立芳); Han ZW(韩占文); Zhang FH(张奉辉)
刊名	MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
	2004-12-21
卷号	355 期号:4 页码:1383-1398
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, Natl Astron Observ, Yunnan 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 without angular momentum loss (AML). The models exhibit cyclic behaviour about a state of marginal contact on a thermal time-scale. Part of the time of each cycle is spent in contact and part in a semidetached state. According to observations, W UMa systems suffer AML. We present the models of low-mass contact binaries with AML due to gravitational wave radiation or magnetic stellar wind (MSW). We find that gravitational radiation cannot prevent the cyclic evolution of W UMa systems, and the effect of gravitational radiation on the cyclic behaviour of contact binary evolution is almost negligible. We also find that the most likely AML mechanism for W UMa systems is magnetic braking, and that magnetic braking effects can increase the period of the cyclic evolution and shorten the fraction of the time spent in the poor thermal contact state exhibiting EB light curve. If W UMa stars do not undergo cyclic evolution, and their AML is caused simultaneously by MSW of both components, we find that the value of the parameter, lambda, should be taken as about 3.8 for W UMa systems, which is larger than the largest value of similar single stars derived from observations. This indicates that the AML efficiency in W UMa systems may be lowered in comparison with non-contact stars because of less mass contained in the convective envelopes of the components in W UMa systems or some feedback mechanism which may have an effect on W UMa systems. If W UMa systems lose their angular momentum at a constant rate, an angular momentum rate of d ln J/dt approximate to 1.6 x 10(-9) yr(-1) can prevent the cyclic behaviour of the model, and the model can keep in good contact with an essentially constant depth of contact.
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]	CLOSE BINARY-SYSTEMS ; X-RAY BINARIES ; CONTACT BINARIES ; GRAVITATIONAL-RADIATION ; MAGNETIC BRAKING ; CATACLYSMIC VARIABLES ; STELLAR EVOLUTION ; STARS ; EMISSION ; SAGITTAE
收录类别	SCI
原文出处	http://mnras.oxfordjournals.org/content/355/4/1383
语种	英语
WOS记录号	WOS:000225636100034
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/4406]
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 - II. With angular momentum loss[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2004,355(4):1383-1398.
APA	Li LF,Han ZW,&Zhang FH.(2004).Structure and evolution of low-mass W Ursae Majoris type systems - II. With angular momentum loss.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,355(4),1383-1398.
MLA	Li LF,et al."Structure and evolution of low-mass W Ursae Majoris type systems - II. With angular momentum loss".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 355.4(2004):1383-1398.