Plausible explanations for the variations of orbital period in the old nova DQ Herculis

	Plausible explanations for the variations of orbital period in the old nova DQ Herculis
	Dai ZB(戴智斌)1,2,3 ; Qian SB(钱声帮)1,2
刊名	ASTRONOMY & ASTROPHYSICS
	2009-09
卷号	503 期号:3 页码:883-U265
关键词	stars: novae cataclysmic variables stars: binaries: eclipsing stars: individual: DQ Herculis
ISSN号	0004-6361
通讯作者	Dai, ZB (reprint author), Chinese Acad Sci, Yunnan Observ, Natl Astron Observ, POB 110, Kunming 650011, Peoples R China.
产权排序	第一完成单位
英文摘要	Aims. Several mechanisms are presented to explain the observed small variation in the orbital period of the old nova DQ Herculis. Methods. We have combined two new CCD times of light minimum of DQ Herculis with all 226 available times of light minimum, including 79 visual observations, for the new orbital period analysis. Results. Based on this analysis, the best-fit of the O-C diagram for DQ Herculis is a quadratic-plus- sinusoidal fit. A secular orbital period increase with a rate of 9.5(+/- 0.1) x 10(-12) s s(-1) is confirmed, which corresponds to a lower limit of the mass transfer rate of 7.2(+/- 3.2) x 10(-9) M(circle dot) yr(-1). We investigate three plausible mechanisms (direct change of the red dwarf's radius, Applegate's mechanism and the light travel-time effect) to explain the quasi-periodic variation shown in the O-C diagram. Although previous works have suggested that solar-type magnetic cycles in the red dwarf can explain the quasi-periodic variation in the orbital period, we were not able to reproduce this finding. Accordingly, a light trave-time effect is proposed, with a brown dwarf as a tertiary component with a significance level of greater than or similar to 77.8% orbiting around nova DQ Herculis. In order to interpret the small departure from the best-fit near 60 000 cycles, we assume an eccentric orbit of the third body with a small eccentricity. However, a satisfying result was obtained because the eccentricity e = 0.12 is close to zero. The parameters of this elliptical orbit are similar to that of a circular orbit.
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]	RAPID BLUE VARIABLES ; 71 2ND OSCILLATION ; CATACLYSMIC VARIABLES ; U-GEMINORUM ; BINARIES ; ECLIPSE ; PHOTOMETRY ; PROFILE ; SYSTEM ; STARS
收录类别	SCI ; EI
原文出处	http://www.aanda.org/articles/aa/abs/2009/33/aa10909-08/aa10909-08.html
语种	英语
WOS记录号	WOS:000269727100025
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/5819]
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
推荐引用方式 GB/T 7714	Dai ZB,Qian SB. Plausible explanations for the variations of orbital period in the old nova DQ Herculis[J]. ASTRONOMY & ASTROPHYSICS,2009,503(3):883-U265.
APA	Dai ZB,&Qian SB.(2009).Plausible explanations for the variations of orbital period in the old nova DQ Herculis.ASTRONOMY & ASTROPHYSICS,503(3),883-U265.
MLA	Dai ZB,et al."Plausible explanations for the variations of orbital period in the old nova DQ Herculis".ASTRONOMY & ASTROPHYSICS 503.3(2009):883-U265.