| 其他摘要 | The K-type close binaries is a category of close binaries with K-type spectra. Broadly speaking, they can be made of dwarf component stars or giant stars. The latter have already finished their main-sequence evolution. This paper mainly discuss the objects with very short periods whose components are mostly similar to dwarf stars. They are divided into the contact type and the near contact type and then discussed. The near contact type consists of EA type and EB type variables in our classification. In this paper, the author presents an overview of the current progress in the research of the K-type close binaries; gives an introduction of the photometric and spectroscopic methods; presents the analysis of a group of observed K-type close binary samples, including six contact samples and one near contact sample; makes a statistic study of the collected K-type close binary samples. The main contents and results are shown as follows. 1. Through photometric solutions of the contact samples, the light curves and the orbital parameters (e.g. inclination and mass ratio ) are derived. The degrees of contact, configurations and temperature relationship are also derived. It is discovered that all of them are shallow contact, W-type systems. The temperature differences between the components of them are about 0 to more than 200 K. The lowest degree of contact is 3.5\% which belongs V1799 Ori, and the highest is 17\% that belongs to J0529. The LCs (light curves) of J0529 are distinctively different from that of other samples. The secondary eclipse of the former is flat, which is similar to that of A-type. Its temperature difference is the smallest, the secondary is only slight hotter than the primary. Its mass ratio is smaller than 0.4, which is the smallest among the analyzed samples. Its period is the shortest, only 0.227 days, which is very close to the cut-off period of contact binaries. The mass ratio of BI Vul is close to the unit 1, and its degree of contact is also low, only 8.7\%, which implies that the object may just evolve into the contact stage. 2. Through period analysis of the contact samples, RV CVn is discovered to keep a long-term stable period. Its period is found to have no obvious change during the past almost 90 years. Only periodic oscillation with period of about 60 years is presented. Three of the rest samples show decreasing periods and only V1799 Ori has a weak increasing period. Four contact binaries are found to show periodic oscillation in their orbital period. Among them ,V1104 Her seems to have two periodic components, which meets the near-integer-ratio. Therefore the most plausible explanation is two stellar companion with small masses in the outer orbits, the orbital resonance helps the outer triple system to keep stable. 3. It is discovered that the near contact binary DV Psc is a highly active system. The photometric mass ratio is locally in agree with the spectroscopic result. Both of them are around 0.7. The fill factors of the two components stars are calculated to be 86\% (primary) and 88\% (secondary). The fill factors of the secondary is a little higher than that of the primary, which indicates that the volume of the secondary may be oversized. The LCs of DV Psc show strong asymmetry, as well as distortion and fast changes, which makes the spot solutions with large uncertainties. The surface activities of the system strongly affect the LCs, thus influence the determination of times of minimum light. Therefore the data which is strongly affected is not used and then a periodic oscillation with a period of close to 2.5 years and a amplitude of close to 0.001 days is found, as well as a uncertain long-term increase. In consideration of a large fraction of a third light in the system, the periodic oscillation may be caused by an additional companion, which may revolve around the binary with a high inclination relative to the binary orbit. 4. From the statistic study of 40 K-type contact binary |
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