Observation And Investigation On G-type Solar-like Close Binaries

The components of G-type solar-like close binaries are late-type stars, which exhibit stronger magnetic activities than that sun does, e.g., X-ray mission, stellar spots, and ?ares. The long-term monitoring on these systems are helpful for understanding the magnetic activities and evolutions of solar-like stars in extreme physical conditions(fast rotation, common convective envelop). In this paper,the background, signi?cance, and method of G-type close binaries are introduced in the ?rst section. Later, we carried out the photometric investigations on some contact and semi-detached binaries. At last, the statistical studies and simple analysis of Kepler G-type close binaries are presented. All results are obtained as follows:1、 There are short-time variations of light curves for di?erent geometrical binary systems. Compared with these curves, it was found that the range of variations have the following relations, detached > semi-detached > contact.Based on some present theories, the variations of light curves are possibly due to magnetic activities, which have e?ect on the radius of the components or the common convective envelop. In order to analyze these curves by using WilsonDevinney code e?ciently, we compiled some programs to derive photometric solutions.2、 According to the photometric analysis on G-type contact binaries, CW Cas, GN Boo, and V2284 Cyg, the O’Connell e?ect of CW Cas in 2004 disappeared in 2011; for GN Boo, O’Connell e?ect occurred on 5th, May 2011, and the di?erence between the primary and secondary minimum increased gradually from 2010 to 2013. The ?are-like events are found for V2284 Cyg, but it need to con?rm these with short-exposure observations. By using the W-D code, we derive their photometric solutions. The dark spot of CW Cas in 2011 are smaller than that in 2004; spots on the surface of the primary component for GN Boo are variable. These investigations suggested the common envelop inhibits magnetic activities; the magnetic activities may in?uence the outer radius of the compo-nents, and further lead to the common envelop to vary. Meanwhile, the variations of their orbital periods show the periodical oscillation, which is explained as the presence of the third body.3、The multi-color CCD photometric observations of the Algol-type binary BU Vul were carried out in 2010, June, July, August, and September, respectively.It was found that the obvious variations and asymmetry of light curves on the timescale of month, indicating high-level stellar spot activities on the surface of at least one component. The photometric solutions suggest that BU Vul is a semidetached binary with the cool, less massive component ?lling with the critical Roche-lobe. Meanwhile, all CCD times of minimum light were used to analyze the orbital period variations. From the O-C curve, its orbital period shows a cyclic oscillation(T3=24.5 yr, A3=0.0131 days) superposed on the secular increase. The continuous increasing is possibly as a result of mass transfer from the less massive component to the more massive one at a rate of dM/dt =-2.16×10-7M⊙ year-1.A probable eclipse-like event was observed on November 4th, 2009, what hints that BU Vul has the possibility to be in a quadruple system. From the surveys on1 RXS J201607.0+251645, the variations of light curves are explained for magnetic activity on the surface of the components. It is a excellent sample to study darkspot activities.4、 Based on more than 2500 binaries from Kepler space telescope, we obtained some results, 1) most of temperatures of close binaries range from 5000 K to 6000 K; 2) G-type solar-like detached binaries cover nearly to 70%, number of period less than 10 days up to 67%; 3) the most period of G-type close binaries are between 0.3 days and 0.4 days. The third body was found from the continuous curves or O- C diagram, we also desire to ?nd magnetic activities. Some G-type close binaries show ?ares and O’Connell e?ect. Especially, the di?erence of minimum light for KIC 8481574 are similar with that of GN Boo. By the least square method, we calculated the magnitudes of extreme light and the values of O-C, which were found to be uncorrelated.