| 其他摘要 | Early-type contact binaries in the Large Magellanic Cloud are interacting binary systems consisting of two stars of spectral types O, B and A that both fill their respective Roche lobes and share a common envelope. Secondly, the metal abundance of the Large Magellanic Cloud is significantly lower than that of the solar, which adds to the mystery of the formation and evolution of early-type contact binaries. In the last two decades, Optical Gravitational Lensing Experiment project such as OGLE, MACHO, and EROS have discovered thousands of different types of eclipsing binaries in the Large Magellanic Cloud. The different projects have left a huge database of observations, which is important for the study of all types of eclipsing binaries. Some of the early-type detached binaries in the Large Magellanic Cloud have been used to measure the geometric distances of galaxies. Eclipsing binaries with high eccentricity are used to study the Apsidal Motions. Partially massive contact or near-contact binaries have been used to study the period-luminosity-color relation. A number of B-type eclipsing binaries with periods of 20-50 days have been studied to obtain the relevant physical parameters, statistical relations of the mass ratio distribution, and their evolution. However, the study of early-type contact binaries is almost a gap. Relying on the 1.3-m optical gravitational lensing survey telescope of the OGLE project, our study of 497 contact binaries in the Large Magellanic Cloud, obtaining their physical parameters (e.g. mass, radius, luminosity, temperature, orbital inclination, conjunctions, etc.), analyzing their evolutionary trajectories, determining the age of the system, and accounting for their period-color-luminosity relations and mass ratio distribution will be a great help to study the gap will be greatly filled and is an urgent problem in this research field. The early-type contact binaries in the Large Magellanic Cloud are bright enough, while their relatively short orbital periods make them easy to detect even in short observations. In summary, the Large Magellanic Cloud becomes the ideal astrophysical laboratory to study early-type contact binaries.We selected 497 contact binaries in the OGLE-IV data as the study sample. The I-band magnitude range of objects presented in our sample is from 12.73 mag to 19.898 mag. The V-band magnitude range of objects presented in our sample is from 13.187 mag to 20.598 mag. The V-I ranges from -0.217 mag to 2.774 mag, with the peak of V-I around 0.1, which accounts for half of the sample, indicating that most are early-type stars. By analyzing the color–magnitude diagram, we find that most of the sample is located on the main sequence. The orbital period of the sample ranges from 0.13564 to 126 days, with a peak around 0.8 days. Thirty-two early-type contact binaries were selected as study targets from a sample of 497 based on the following requirements: (1) V-I values between -0.2 and 0; (2) orbital periods of about 0.8 days; and (3) two poles of almost equal depth and typical EW type light curves. To understand its geometrical structure and evolutionary state, the V and I light curves were analyzed using the W–D method.The metal abundances of stars in the Large Magellanic Cloud are significantly lower than those of the Sun, and there are links and differences in whether the differences in metal abundances have a bearing on star formation and evolution. Therefore, the second work chose TW Cas in the Milky Way for its photometric study. TW Cas is an eclipsing binary that contains B-type and solar-like components with an orbital period of 1.42832665 d and mass ratio of 0.4873. The semi-detached configuration makes it a key goal for understanding Algol-type eclipsing binaries evolution. However, the physical parameters and evolutionary state of TW Cas are still unknown. W–D differential correction program was employed to give orbital parameters and configuration and extend our knowledge of TW Cas evolution. We present light curves and 64 eclipsing times observed by Transiting Exoplanet Survey Satellite (TESS) telescope. Photometric analyses of the TESS light curve suggest that TW Cas is a semi-detached system where the less massive component is filling its critical Roche lobe, and a large dark spot is found on the polar of the less massive one. By using all light minima times, it is detected that the O-C curve shows an upward parabolic change while a cyclic oscillation is superimposed with an amplitude of 0.024585 days and a period of 113.41 yr. The upward parabolic change may indicate a long-term increase of the orbital period at a rate of , which reveals a rapid mass transfer between the components. The cyclic oscillation might result from the light-travel-time effect owing to the presence of a third body. The semi-detached configuration that less mass component fills its Roche lobe, together with the long-term increase of orbital period and the presence of a large dark spot on the less massive component indicates that TW Ca is at a critical stage of evolution after a mass ratio inversion. |
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