A New CCD Photometric Investigation of the Short-Period Close Binary AP Leonis

Qian, S.‐B.; Fang, Xiang; Zhu, L.-Y.; Dai, Zhenwen; He, Ji Zheng; Yuan, Jianfeng

doi:10.1086/509499

Cited by 59 publications

(31 citation statements)

References 25 publications

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“…As displayed in the figure, all times of minimum light are best-fit by the quadratic plus light-time ephemeris. This type of period variation occasionally appears in contact binaries and resembles those of some recently studied systems, such as RW Com (Qian 2002), V417 Aql (Qian 2003), BX Peg (Lee et al 2004), FG Hya (Qian & Yang 2005), and AP Leo (Qian et al 2007). The orbital period of each of the systems has varied in some combination of a long-term period decrease and a cyclic variation, where the latter could reasonably be interpreted as either a light-time effect due to an additional object in a close binary, or as period modulation due to a magnetic activity cycle of the solar-type component.…”

Section: The O -C Variation and Its Implicationssupporting

confidence: 77%

A Period Study and Spot Model for the Eclipsing Binary TU Bootis

Lee

Kim

2007

PUBL ASTRON SOC PAC

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ABSTRACT. We present the photometric properties of the eclipsing binary TU Boo from detailed studies of the period and light variations, based on our new BVR observations and historical data collected from the literature. A total of 349 times of minimum light over 80 yr, including our four timings, were used for the period study. An analysis of the resulting diagram reveals that the orbital period of TU Boo has varied in a quasi-sinusoidal O-C way superposed on a long-term period decrease. The secular variation presumably indicates that mass is thermally transferred from the more massive primary star to its companion at a rate of about 7.24 # 10 Ϫ8 M , yr Ϫ1 . The period and semiamplitude of the cyclical variation are 54.5 yr and 0.0177 days, respectively, which could be produced by either a light-time effect or a magnetic activity cycle. Our light curves are asymmetrical, with max I about 0.02-0.03 mag brighter than max II. Among possible spot models, the light variations were bestfit by using a two-spot model with both a cool spot and a hot spot on the secondary star. These may be formed by a combination of effects from a magnetic dynamo and mass transfer. We suggest that TU Boo is probably a triple system, consisting of a massive primary star with a spectral type of G3, a secondary component of spectral type G5-6, and a low-mass M-type tertiary companion with a minimum mass of about p 0.34 M , . M 3

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Section: The O -C Variation and Its Implicationssupporting

confidence: 77%

A Period Study and Spot Model for the Eclipsing Binary TU Bootis

Lee

Kim

2007

PUBL ASTRON SOC PAC

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“…There may exist a secular period decrease superimposed on a sinusoidal oscillation, although there is a long gap between 1944 and 1989. This kind of combination of a period decrease and a cyclic variation also appears in many other overcontact binaries, such as VW Cep (Kaszas et al 1998), AP Leo (Qian et al 2007c), V502 Oph (Yüce et al 2006), and BX Peg (Lee et al 2004). For BS Cas, the continuous period decrease rates can be estimated to be dP /dt = −2.45 × 10 −7 dyr −1 from Equation (2) and dP /dt = −1.51 × 10 −7 dyr −1 from Equation (5), respectively.…”

Section: Discussionmentioning

confidence: 62%

A Photometric Study of the Neglected Eclipsing Binary Bs Cassiopeiae

Yang

Wei

2008

The Astronomical Journal

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We present multicolor charge-coupled device (CCD) photometry for the eclipsing binary BS Cassiopeiae, observed on four nights between 2007 December and 2008 January. Using the Wilson-Devinney program, the photometric solution was derived from our BVR observations. Photometric results indicated that BS Cas is a W-subtype binary, whose mass ratio and overcontact degree are q = 0.2834(±0.0010) and f = 31.6%(±1.1%), respectively. Light curves of BS Cas present a typical O'Connell effect, which may be attributed to dark spot activity of the primary component. A detailed period analysis reveals that there exists a cyclic variation overlaying a secular period decrease, based on either all available light minimum times or recent light minimum times since 1989. The low-amplitude cyclic variation with a period of about 13 yr can be explained by either the lighttime effect or cyclic magnetic activity of both components. The long-term orbital period decrease suggests that BS Cas is undergoing mass transfer from the primary component to the secondary one. With its mass transfer and accompanying angular momentum loss, this binary will evolve into a deeper contact configuration.

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“…The period gap is indicated by vertical dashed lines. The crosses depict ∆P/P values for 56 other close binaries with cyclical period modulations (Lanza & Rodonó 1999;Qian et al 1999Qian et al , 2000aQian et al ,b, 2002Qian et al , 2007aLanza et al 2001;Kang et al 2002;Qian 2002aQian ,b, 2003Yang & Liu 2002, 2003aZavala et al 2002;Çakırlı et al 2003;Kim et al 2003;Qian & Boonrucksar 2003;Afşar et al 2004;Lee et al 2004;Yang et al 2004Yang et al , 2007Zhu et al 2004;Borkovits et al 2005;Erdem et al 2007;Pilecki et al 2007;Szalai et al 2007). Systems with independent evidence that the observed (O−C) modulations can be explained by a third body were excluded (actually, it is not possible to exclude the possibility that the observed modulation of some of the systems plotted may still be caused by a third body.…”

Section: A Comparison Of the Observed Orbital Period Modulations Abovmentioning

confidence: 99%

Cyclical period changes in HT Cassiopeiae: a difference between systems above and below the period gap

Baptista

Papadimitriou

Giannakis

2008

A&A

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Aims. We report identification of cyclical changes in the orbital period of the eclipsing cataclysmic variable HT Cas. Methods. We measured new white-dwarf mid-eclipse timings and combined them with published measurements to construct an observed-minus-calculated diagram covering 29 years of observations. Results. The data present a 36 yr period modulation of semi-amplitude ∼40 s, with a statistical significance greater than 99.9 percent with respect to a constant period. Conclusions. We combine our results with those in the literature to revisit the issue of cyclical period changes in cataclysmic variables and their interpretation in terms of a solar-type magnetic activity cycle in the secondary star. A diagram of fractional period change (∆P/P) versus the angular velocity of the active star (Ω) for cataclysmic variables, RS CVn, W UMa, and Algols, reveal that close binaries with periods above the gap (secondaries with convective envelopes) satisfy a relationship ∆P/P ∝ Ω −0.7±0.1 . Cataclysmic variables below the period gap (with fully convective secondaries) deviate from this relationship by more than 3-σ, with average fractional period changes 6 times smaller than those of the systems above the gap.

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A New CCD Photometric Investigation of the Short-Period Close Binary AP Leonis

Cited by 59 publications

References 25 publications

A Period Study and Spot Model for the Eclipsing Binary TU Bootis

A Period Study and Spot Model for the Eclipsing Binary TU Bootis

A Photometric Study of the Neglected Eclipsing Binary Bs Cassiopeiae

Cyclical period changes in HT Cassiopeiae: a difference between systems above and below the period gap

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