| 其他摘要 | A-type stars are a class of stars that exhibit the most pronounced Balmer line features, lying between early and late-type stars. They have high temperatures, appearing white or bluish-white, with generally weak activity, making them an important stellar category. A-type eclipsing binaries (EBs) refer to binary systems in which the primary star is of the A-type. These EB systems evolve more slowly than their early-type coun terparts, offering a sufficient number of observable samples for study in the universe. Compared to late-type EBs, they lack significant activity, rendering them ideal natural laboratories for studying binary evolution and mass transfer without interference from magnetic activity. Despite their importance, comprehensive research on A-type EBs remains scarce, warranting systematic investigation of these binary systems. In recent years, the release of high-precision photometric surveys and vast spectroscopic survey data has led to the discovery of numerous A-type EBs. This paper, based on such survey data, screens A-type EBs, combines follow-up observations from domestic and interna tional ground-based telescopes, and identifies a set of peculiar A-type EBs. Detailed analyses of selected targets explore their mass transfer processes and preliminary sta tistical characteristics, with the main research accomplishments outlined as follows: 1. Discovery of A-type near-contact binaries with extreme mass ratios, revealing mass ratio inversions leading to the formation of low mass ratio contact systems. CSS_J154915.7+375506 is an A-type total-eclipse EB with EB-type light variability. Analysis of its BVRI multi-color complete light curves obtained from the 1.5-meter tele scope in Uzbekistan reveals it to be a nearly-contact binary system with an extremely low mass ratio of 0.138. The secondary star is more evolved than the primary and has a higher surface effective temperature than a star of comparable mass, indicating sub stantial mass loss and subsequent mass ratio inversion. Analysis of its orbital period suggests a long-term decrease superimposed with periodic variations, with the latter potentially stemming from a third body with a mass exceeding 0.91M⊙ . However, the negligible contribution of a third light component in the light curve analysis implies that this third body might be a compact object. As the orbital period decreases, this system will evolve into a contact binary, possessing an extreme mass ratio at the time of contact formation. 2. Analysis of five EA-type spectral A type total-eclipse EBs(C025311.42+470916 .5, C051224.47+320023.2, C052148.71+020846.1, C065601.63+004938.5, and C070 916.09+383934.5), all found to be detached binary systems with low fill-out factors. Employing both WD and PHOEBE software to derive parameters from their TESS light curves, the results obtained from each method are consistent within error margins. Due to the limited observation duration precluding detection of orbital period changes in these targets, we merely update their periods. Placing these systems on the Hertzsprung-Russell (HR) diagram and comparing them with A-type contact binaries, it is observed that the two components of A-type detached binaries are both situated near the terminal-age main sequence, with comparable evolutionary stages. Conversely, in the majority of A-type contact binaries, the primary star resides near the terminal-age main sequence while the secondary lies close to the zero-age main sequence, indicating a significantly higher evolutionary stage for the primary. A-type detached binaries typically have longer periods, and detailed studies on such systems are relatively scarce; further statistical analyses await accumulation of additional samples. |
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