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New CCD photometric investigation of the early-type overcontact binary BH Cen in the young star-forming Galactic cluster IC 2944

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Research in Astronomy and Astrophysics 2018年第5期18卷 119-130页

作者： Er-Gang Zhao Sheng-Bang Qian Miloslav Zejda Bin Zhang Jia Zhang Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China Department of Theoretical Physics and Astrophysics Masaryk University Brno Czech Republic

BH Cen is a short-period early-type binary with a period of 0.792^d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A3 = 0.024 d and a period of P3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass *** continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of˙M2 = 2.8×10^-6 M⊙per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M⊙ at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.

关键词： binary (including multiple) close - stars binaries eclipsing - stars early-type - stars evolution - stars individual (BH Cen)

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First photometric study of ultrashort-period contact binary 1SWASP J140533.33＋114639.1

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Research in Astronomy and Astrophysics 2018年第3期18卷 57-62页

作者： Bin Zhang Sheng-Bang Qian Ri Michel Boonrucksar Soonthornthum Li-Ying Zhu Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China Instituto de Astronomia UNAM Ensenada Mexico National Astronomical Research Institute of Thailand Chiang Mai 50200 Thailand

In this paper,CCD photometric light curves for the short-period eclipsing binary 1 SWASP J140533.33＋114639.1（hereafter J1405） in the BV R bands are presented and analyzed using the 2013 version of the Wilson-Devinney（W-D） code. It is discovered that J1405 is a W-subtype shallow contact binary with a contact degree of f = 7.9±0.5% and a mass ratio of q = 1.55±0.02. In order to explain the asymmetric light curves of the system,a cool starspot on the more massive component is employed. This shallow contact eclipsing binary may have been formed from a short-period detached system through orbital shrinkage due to angular momentum loss. Based on the（O-C） method,the variation of orbital period is studied using all the available times of minimum light. The（O-C） diagram reveals that the period is increasing continuously at a rate of d P/dt = ＋2.09×10^-7 d yr^-1,which can be explained by mass transfer from the less massive component to the more massive one.

关键词： stars binaries close - stars binaries eclipsing - stars individual (1SWASPJ140533.33+114639.1)

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A Photometric Study of the W UMa-Type Contact Binary RZ Com

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Chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 465-471页

作者： Jia-Jia He Sheng-Bang Qian National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China United Laboratory of Optical Astronomy Chinese Academy of Sciences （ULOAC） Beijing 100012 China Graduate School of Chinese Academy of Sciences Beijing 100049 China

We present results of CCD photometric observations of the short-period W UMatype contact binary system, RZ Com. The light curve of the binary has changed from Wsubtype to A-subtype from 1998 to 2003, then back to W-subtype in 2004. An analysis was carried out using the 2003 version of the Wilson-Devinney code. It is confirmed that RZ Com is a low-degree, overcontact f = 20.1% （±7.4%） binary system with a high inclination of i = 81.°40 （＋0.°40）, and a mass ratio q = 2.351 （＋0.031）. Combining four newly determined times of light minimum with others in the literature, the variations in orbital period is examined. A small-amplitude oscillation （A=0.0065d）, with a period of 41.5 year, is discovered superimposed on a long-term increase at rate dP/dt = ＋3.97 × 10^-8d yr^-1. The period oscillation can be explained either by the light-time effect due to the presence of an unseen third body, or by cycles of magnetic activity on the components. Combining our photometric solution with the spectroscopic elements obtained by Mclean ＆ Hilditch, the absolute dimensions ofRZ Com are： M1 = 1.14 （±0.19）M⊙, M2 = 0.50 （±0.09）M⊙, R1 = 1.12 （±0.01）R⊙, R2 = 0.78 （＋0.01）R⊙ and A = 2.41 （±0.02）R⊙.

关键词： stars binaries close - stars binaries eclipsing - stars individual RZ Com

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Investigations into the thermal non-equilibrium of W UMa-type contact binaries

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Research in Astronomy and Astrophysics 2018年第5期18卷 83-92页

作者： Xiao Xiong Liang Liu Sheng-Bang Qian Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China

Traditionally, some physical details（e.g., magnetic braking, energy transfer, angular momentum loss, etc.） have to be taken into consideration during investigations into the evolution of contact binaries. However, the real evolutionary processes which usually contain several of these physical mechanisms are very complicated as a result of strong interaction between components. To avoid dealing with these factors, a linear relationship is applied to the temperatures of components. It is found that the higher the mass ratio（M2/M1） of a contact system, the weaker the deviation from thermal *** this basis, a variation trend of fill-out factor（f） changing with mass ratio can be inferred, which is consistent with observations. Moreover, if we stick to this point of view, it should be natural that the number of semi-detached binaries in the predicted broken-contact phase of relaxation oscillations is less than the number in the contact phase.

关键词： stars binaries close - stars binaries eclipsing - stars evolution

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Possible modulated γ-ray emission from the transitional millisecond pulsar binary PSR J1023+0038

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Research in Astronomy and Astrophysics 2018年第10期18卷 109-116页

作者： Yi Xing Zhong-Xiang Wang Jumpei Takata Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences School of Physics Huazhong University of Science and Technology

We report the results from our analysis of Fermi Large Area Telescope （LAT） data for the transitional millisecond pulsar binary PSR J1023＋0038. The time period of the data is nearly 9 yr, and that after the source＇s transition, in June 2013 from the disk-free state to the active state of having an accretion disk, is approximately 4 yr. We identify a high-energy 〉5.5 GeV component in the source＇s spectrum in the active state, and find this component is only significantly detected in half of the orbital phase centered at the descending node （when the pulsar is moving towards the Earth）. Considering the pulsar scenario proposed for multi-frequency emission from the source, in which the pulsar is still active and a cold-relativistic pulsar wind inverse-Compton scatters the photons from the accretion disk, we discuss the origin of the high-energy component. In order to explain the observed spectrum, a power-law distribution of particles, with an index of ~3, in the pulsar wind is required, while the orbital variations are possibly due to changes in power-law index as a function of orbital phase.

关键词： gamma rays stars - binaries eclipsing - stars neutron

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Orbital period changes of the W UMa binary YY Eri

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Research in Astronomy and Astrophysics 2018年第9期18卷 13-20页

作者： Ting Yu Ke Hu Yun-Xia Yu Fu-Yuan Xiang Department of Physics Xiangtan University

Orbital period changes of the W UMa-type binary YY Eri are analyzed by using all photoelectric and ccd times of light minimum. The results show that its orbital period is undergo- ing a secular increase superposed on two cyclic oscillations. The continuous increase at the rate of dP/dt = 6.3806 × 10^-8 d yr^-1 may be accounted for by mass transfer from the less massive com- panion to the more massive one. Two periodic variations with periods of 38.6192 and 22.3573 yr may be attributed to the light-time effect of a faint third star and the cyclic magnetic activity of the system, respectively.

关键词： stars binaries close - stars binaries eclipsing - stars individual (YY Eri)

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