| 其他摘要 | Eclipsing Algols are eclipsing binaries with Algol paradox, meanwhile present EA/EB type light curves. Algol-type binaries are special kind of close binaries, which has very important research significance: (a). As a eclipse system, its time domain light curve during eclipsing is sharp and deep, which is convenient for accurately acquiring the eclipse timing; (b). Among all types of close binaries, the eclipse timing variation (ETV) data of Algol-type binaries have the longest accumulation time in history, therefore, it is most beneficial to study the ETV and orbital period evolution; (c). It is also a natural laboratory for studying mass transfer. Mass transfer plays a key role in the evolution of binary stars and is an important physical process that distinguishes the evolution of single and double stars. We conducted a statistical analysis of the Algols, and selected some typical and special samples for detailed ETV and observational studies, including three long-period samples, two short-period samples, and two related types of samples, and achieved the following research results:1. Statistical AnalysisWe collected the Algols in the Kepler sky area, and matched with data from LAMOST and Gaia and the stellar evolution database to obtain 176 samples; and 1002 Algols in the vsx catalogue. The physical parameters for these samples are: orbital period, primary stars' spectral type, mass, radius, surface temperature, surface gravity acceleration, metal abundance, radial velocity, age, distance etc. Some statistical relations are obtained, which can be applied to the subsequent research work.2. Longer Period Samples（P > 1 d）RR Dra is a classic Algol-type eclipsing binary star with an orbital period of about 2.83 days. After an analysis of the changes in its orbital period over a 120-year data span, it is found that the orbital period is undergoing a long-term increase process with a rate of 2.4(±0.3) × 10 −6 d/yr. At the same time, there is also a periodic oscillation with the period of 98.2 years and an amplitude of 0.134 days, which could be explained by a celestial body with the mass up to 3.6 solar mass. After analysing the light curves by TESS, it was found that the third light contributed to only 1-2 %, and it could be explained by the photometric contribution of the 16 mag nearest star. Then the third celestial body does not emit light, but with the mass of larger than 3.6 solar mass, it can only be a black hole candidate. BO Gem and SX Lyn are eclipsing binaries with periods of approximately four and two days, respectively. The analysis of their orbital period found that there is a massive third celestial body, but no third light contribution found in the photometric solution, suggesting that there are black hole companion candidates around both systems. Because the orbital period is close to an integer day, it is difficult to observe the complete light curve on the ground. The space telescope projects like K2 and TESS observed the light curves of these two samples over multiple periods, and found that they are both EA-type light curve like Algols. After analysing the light curve, the preliminary results indicat that they are all detached binary stars. Further research is needed on these two sources.2. Short Period Samples（0 < P < 1 d）SX Psc is an eclipsing binary star with the orbital period of about 0.8358808 d. After the observation by the Xinglong 80 cm telescope, the complete periodic light curve were obtained, and the data was analysed. The results show that this is a total eclipsing Algol binary with the orbital inclination angle of 89 degrees, the primary star's filling degree of 85 %, and the small massive secondary star filled its Roche lobe. After the analysis of its orbital period it is found that the long-term orbital period increase rate is 4.64(4) × 10 −8 d/yr. Under the conservative observation, the mass transfer rate is 1.96×10 −8 M ⊙ /yr. At the same time, there is also a small periodic variation. It is analysed with the light-time effect model, and found that this periodic change may be caused by a brown dwarf candidate. XZ CMi is a controversial short-period eclipsing binary star in history, of which the orbital period is 0.578809 d. Our research work proposes a new model that solves the fitting problem of new O −C data that does not match the periodic variation of the fitting curve trend. Also, a third-body with the mass of about 0.42 solar mass were detected. We also observed the complete light curve, and be aware of that it is an Algol-type near-contact eclipse binary with the primary star's filling degree of about 91%, and a small mass secondary star filled its own Roche lobe. At the same time, we observed and found a visual companion star, and conducted spectroscopic observation to XZ CMi. Under the joint analysis of astrometric and spectroscopic data, we can know that this is a non-homogeneous multiple system.In addition, our results perfectly made an explain for the dis-accordance between the third light and the third celestial body.3. Related SamplesWith mass transfer and angular momentum loss, a near-contact binary will evolve to be a contact binary. V1005 Her is a solar-like eclipsing binary with a short orbital period of 0.27895803 d. Through the analysis of 7 years of monitoring, we found that it is a shallow contact active binary. Light curves change with time, the orbital period changes with time. Although it is an active binary system, the energy of its active sub-star is insufficient to explain this cyclic period change. It is caused by a third object with a minimum mass of 0.45 M ⊙ . In addition, NSVS1425 is an OB-type sub-dwarf binary (sdOB+dM) system, showing the same EA-type light curve as the Algols, but unlike the Alogls, it is formed after undergoing the ejection of common envelope. Analysis of the orbital period reveals that there is a close-in sub-stellar object orbiting the binary pair. The mass of this sub-stellar object is between the planet and the brown dwarf, and may play an important role in the formation of the hot sub-dwarf binary. |
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