Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion

	Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion
	Qian SB(钱声帮)1,2,3 ; Dai ZB(戴智斌)1,2,3 ; He JJ(何家佳)1,2,3 ; Yuan JZ(袁金照)1,2,3 ; Xiang, FY4 ; Zejda, M 5
刊名	ASTRONOMY & ASTROPHYSICS
	2007-05
卷号	466 期号:2 页码:589-594
关键词	stars : novae, cataclysmic variables stars : binaries : eclipsing stars : individual : AC Cnc stars : evolution stars : mass-loss stars : binaries : close
ISSN号	0004-6361
通讯作者	Qian, SB (reprint author), Chinese Acad Sci, Natl Aston Observ, Yunnan Observ, POB 110, Kunming 650018, Peoples R China.
产权排序	第一完成单位
英文摘要	Aims. The source AC Cnc is a nova-like cataclysmic variable containing a white-dwarf primary with a mass of 0.76 M-circle dot and a K2-type secondary with a mass of 0.77 M-circle dot. We intend to study its period changes and search for evidence of magnetic braking and unseen third body. Methods. The period changes were investigated based on the analysis of the O-C curve, which is formed by one new eclipse time together with the others compiled from the literature. Results. A cyclic change with a period of 16.2 yr was found to be superimposed on a long-term period decrease at a rate of. P = -1.24(+/- 0.44) x 10(-8) days/year. Conclusions. It is shown that the mechanism of magnetic activity-driven changes in the quadrupole momentum of the secondary star (Applegate's mechanism) does not explain it easily. This period oscillation was plausibly interpreted by a light-travel time effect caused by the presence of a cool M-type dwarf companion (M-3 > 0.097 M-circle dot) in a long orbit (16.2 yr) around the binary. Since the masses of both components are nearly the same, the mass transfer from the lobe-filling secondary to the primary is not efficient to cause the continuous period decrease. It may be strong evidence of an enhanced magnetic stellar wind from the K2-type component. If the Alfen radius of the cool secondary is the same as that of the Sun (i.e., R-A = 15 R-circle dot), the mass-loss rate should be. M-2 = -1.65 x 10(-10) M-circle dot/year. By using the enhanced mass loss proposed by Tout & Eggleton (1988), the mass-loss rate should be. M-2 = -1.18 x 10(-9) M-circle dot/year. In this case, the Alfen radius is determined to be R-A = 5.2 R-circle dot. However, the long-term decrease of the period may be only a part of a long-period (> 100 yr) oscillation caused by the presence of an additional body. To check the conclusions, new precise times of light minimum will be required.
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 BINARIES ; MODULATION
收录类别	SCI ; EI
原文出处	http://www.aanda.org/articles/aa/abs/2007/17/aa5970-06/aa5970-06.html
语种	英语
WOS记录号	WOS:000245686800021
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/5800]
专题	云南天文台_双星与变星研究组
作者单位	1.National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, PR China 2.United Laboratory of Optical Astronomy, Chinese Academy of Science (ULOAC), 100012 Beijing, PR China 3.Graduate School of the CAS, Beijing, PR China 4.Physics Department, Xiangtan University, 411105 Xiangtan, Funan Province, PR China 5.Institute of Theoretical Physics and Astrophysics, Masaryk University, 611 37 Brno, Czech Republic
推荐引用方式 GB/T 7714	Qian SB,Dai ZB,He JJ,et al. Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion[J]. ASTRONOMY & ASTROPHYSICS,2007,466(2):589-594.
APA	Qian SB,Dai ZB,He JJ,Yuan JZ,Xiang, FY,&Zejda, M.(2007).Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion.ASTRONOMY & ASTROPHYSICS,466(2),589-594.
MLA	Qian SB,et al."Orbital period changes of the nova-like cataclysmic variable AC Cancri: evidence of magnetic braking and an unseen companion".ASTRONOMY & ASTROPHYSICS 466.2(2007):589-594.