| 其他摘要 | Early-type binaries composed with stars whose spectral type is O, B and A-type. Because of the strong interaction between two components, many special phenomenon, such as high energy radiation, mass transfer and loss, stellar winds, are found in early-type binaries. This will provide many chances to study these physical process. They will evolve to be compact stars, and at the end, it may be result in burst of Ia supernove and so on. These make the study on early-type binary to be very important. Based on early-type binaries, this thesis introduces many phenomena in early-type binary stars, such as stellar wind and so on. At same time, it also gives a brief description on model of binary, data acquisition and the method of orbital period change. In this article, some interesting early-type binaries are observed and analysed. The results are listed as following:1. BH Cen is a short-period early-type binary in the extremely young star-formation cluster IC 2944. New multi-color CCD photometric light curves in U,B,V,R and I bands are presented and are analysed by using the Wilson-Devinney Code. It is detected that BH Cen is a high-mass-ratio over-contact 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 total eclipsing binary and the photometric parameters could be determined reliably. By adding new eclipse times, the orbital period changes of the binary are analysed. 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 days and a period of P3=50.3 years. The high mass ratio, the over-contact configuration and the long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary stage after the shortest-period state during Case A mass transfer. The continuously increasing in the period could be explained as the mass transfer from the secondary component to the primary one at a rate of dM2 = 2.8X10-6Msun, per year. The cyclic change could be plausibly explained by the presence of the third body because both components in BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 Msun at an orbital separation 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 of compact object.2. V593 Cen is an early-type contact binary with period of 0.7553 days. New light curves in B,V,R and I bands were observed and another V-band light curve was collected from ASAS data. We analysed the two sets of light curves by using W-D code, respectively. It is detected that V593 Cen is a deep-contact binary with a fill-out factor of more than 45%. The mass ratio is derived to be closed to unit indicating that it contains two twin components. Together with the higher temperature of less massive component, it may be inferred that the system has just passed the mass reversal stage during the mass-transfer evolution. It has the shortest period and deepest-contact configuration at present. By analysing the O-C curve of V593 Cen, the orbital period shows a cyclic variation with a period of 50.9years. This can be explained as the light-travel time effect via the presence of a third body because both components are early-type stars as same as in BH Cen. The mass of the third body is derived to be larger than 4.3 (0.3)Msun and it should contribute to the total light of the system. However, no third light is detected during the photometric analyses. This indicates that it may be a black hole candidate orbiting the central mass-transferring binary in a triple system that is similar to the V Pup system.3. We obtained several new CCD times of light minimum of RZ Pyx. Together with all available photoelectric and CCD times of light minimum, the changes in the orbital period are investigated for the first time. Meanwhile, previously published light curves are reanalyzed with the Wilson-Devinney method. Based on the analysis of the O-C diagram, two cyclic variations with small amplitude are discovered to be superimposed on a continuous increase. The light curve solutions suggest that RZ Pyx is a marginal detached binary system where both components do not overfill their respective Roche lobes. The fill-out factors of the primary and the secondary component are 95.5(0.8)% and 99.1(1.9)% respectively revealing that the secondary is nearly filling out its Roche lobe. This may indicate that RZ Pyx may have underwent a mass-transferring evolutionary stage and it is on the marginal detached stage temporarily. The long-term increase in the orbital period could be explained by enhanced mass loss from the stellar winds of the two detached massive components. Since the two binary components are early-type stars, the two cyclic oscillations could be plausibly interpreted as the results of light travel-time effect caused by the presence of two additional companions.4.The first spectra of CD Cam told us the primary component is an A3 type main sequence star and CCD light curves of the eclipsing binary in Rc and V bands are obtained for the first time and analysed by using W-D code. It shown that it is a shallow-contact binary with a filling-out factor of 22.0 %. The extremely low mass ratio of the binary system (q=0.088) indicates that its A3-type primary is orbiting by a low-mass companion with a mass of 0.22 Msun and a temperature of 8310 K. These results reveal that the secondary may be a remnant of a stripped red giant star. By analysing the O-C curve, we discovered that the orbital period is decreasing continuously. This can be explained by mass exchange from primary to the secondary component. The marginal-contact configuration, the extremely low mass ratio and the period decreasing, all suggest that the secondary may be a remnant of a stripped red giant star and CD Cam may be an offspring of EL CVn-type binaries.5. we obtained the new light curves for A-type binary KN Per and O-type binary MY Cam and found there are O'Connell effect in their light curves. |
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