The origin of subdwarf B stars - II

doi:10.1046/j.1365-8711.2003.06451.x

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	The origin of subdwarf B stars - II
	Han ZW(韩占文)1 ; Podsiadlowski, P 2; Maxted, PFL 3; Marsh, TR 4; Han, Z (reprint author), Chinese Acad Sci, Natl Astron Observ, Yunnam Observ, POB 110, Kunming 650011, Peoples R China.
发表期刊	MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
	2003-05-11
卷号	341 期号:2 页码:669-691
DOI	10.1046/j.1365-8711.2003.06451.x
产权排序	第1完成单位
收录类别	SCI
关键词	Binaries : Close Subdwarfs White Dwarfs
摘要	We have carried out a detailed binary population synthesis (BPS) study of the formation of subdwarf B (sdB) stars and related objects (sdO, sdOB stars) using the latest version of the BPS code developed by Han and co-workers. We systematically investigate the importance of the five main evolutionary channels in which the sdB stars form after one or two common-envelope (CE) phases, one or two phases of stable Roche lobe overflow (RLOF) or as the result of the merger of two helium white dwarfs (WDs). Our best BPS model can satisfactorily explain the main observational characteristics of sdB stars, in particular their distributions in the orbital period-minimum companion mass (log P-M-comp) diagram and in the effective temperature-surface gravity (T-eff- log g) diagram, their distributions of orbital period, log (gtheta(4))(theta = 5040 K / T-eff) and mass function, their binary fraction and the fraction of sdB binaries with WD companions, their birth rates and their space density. We obtain a Galactic formation rate for sdB stars of 0.014- 0.063 yr(-1) with a best estimate of similar to0.05 yr(-1) and a total number in the Galaxy of 2.4-9.5 x 10(6) with a best estimate of similar to6 x 10(6); half of these may be missing in observational surveys owing to selection effects. The intrinsic binary fraction is 76-89 per cent, although the observed frequency may be substantially lower owing to the selection effects. The first CE ejection channel, the first stable RLOF channel and the merger channel are intrinsically the most important channels, although observational selection effects tend to increase the relative importance of the second CE ejection and merger channels. We also predict a distribution of masses for sdB stars that is wider than is commonly assumed and that some sdB stars have companions of spectral type as early as B. The percentage of A-type stars with sdB companions can in principle be used to constrain some of the important parameters in the binary evolution model. We conclude that (i) the first RLOF phase needs to be more stable than is commonly assumed, either because the critical mass ratio q(crit) for dynamical mass transfer is higher or because of tidally enhanced stellar wind mass loss; (ii) mass transfer in the first stable RLOF phase is non-conservative, and the mass lost from the system takes away a specific angular momentum similar to that of the system; and (iii) common-envelope ejection is very efficient.
语种	英语
学科领域	Astronomy & Astrophysics
文章类型	Article
ISSN	0035-8711
URL	查看原文
归档日期	2003-06-04
WOS记录号	WOS:000182651400026
WOS研究方向	Astronomy & Astrophysics
WOS类目	Astronomy & Astrophysics
关键词[WOS]	PALOMAR-GREEN SURVEY ; ULTRAVIOLET-EXCESS OBJECTS ; BINARY STELLAR EVOLUTION ; HYDROGEN-RICH SUBDWARFS ; HORIZONTAL-BRANCH STARS ; MASS-RATIO DISTRIBUTION ; RAPIDLY PULSATING STAR ; INFRARED FLUX EXCESSES ; DOUBLE WHITE-DWARFS ; HOT SUBDWARFS
引用统计	被引频次：576[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/114a53/4403
专题	大样本恒星演化研究组
通讯作者	Han, Z (reprint author), Chinese Acad Sci, Natl Astron Observ, Yunnam Observ, POB 110, Kunming 650011, Peoples R China.
作者单位	1.National Astronomical Observatories/Yunnan Observatory, the Chinese Academy of Sciences, PO Box 110, Kunming, 650011, China 2.University of Oxford, Department of Astrophysics, Keble Road, Oxford OX1 3RH 3.School of Chemistry and Physics, Keele University, Staffordshire ST5 5BG 4.University of Southampton, Department of Physics & Astronomy, Highfield, Southampton S017 1BJ
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	Han ZW,Podsiadlowski, P,Maxted, PFL,et al. The origin of subdwarf B stars - II[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2003,341(2):669-691.
APA	Han ZW,Podsiadlowski, P,Maxted, PFL,Marsh, TR,&Han, Z .(2003).The origin of subdwarf B stars - II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,341(2),669-691.
MLA	Han ZW,et al."The origin of subdwarf B stars - II".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 341.2(2003):669-691.

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