G-type eclipsing binaries' spectral type and internal structure are similar to the Sun's. According to the solar dynamo theory, the magnetic activity of the Sun is due to the interaction of external convection, solar rotation, and differential rotation. In recent years, with the operation of some large-scale sky survey projects, the data resources have been greatly enriched, including many G-type eclipsing binary systems. And these eclipsing binaries are distributed at different locations on the H-R diagram. Some systems, such as deep and low mass ratio contact binaries, are at critical evolutionary stages. Their high-precision photometric and spectroscopic data help explore stars' evolutionary and magnetic activity. In this paper, we first provide an overview of the relevant background and research significance. Then the relevant research methods are described. In the third part of the article, the specific work is presented, and the main findings are as follows: 1. The first multi-color light curves analysis of G-type eclipsing binary V2769 Ori was performed. The photometric solution was obtained with the Wilson-Devinney method. The results show that V2769 Ori is a low-mass-ratio and deep-contact binary with a mass ratio of q = 0.162 and a fill-out factor of f = 55%. The total eclipse characteristics of V2769 Ori indicate that the photometric solution we obtained is reliable. With all available times of minimum light, the O-C diagram was constructed and analyzed. The orbital period analysis reveals a long-term period decrease at a rate of dP/dt = −1.24 × 10−6 d yr−1and a periodic oscillation with a period of 8.77 years. The secular period decrease can be explained by a combination of mass transfer between the two components and the angular momentum loss of the system. As the orbital period decrease, the shrinking of the inner and outer critical Roche lobes causes an increase in contact degree, and the binary system will finally merge into a rapidly rotating single star. Periodic oscillation may be the result of the light travel time effect due to the presence of a faint third body. 2. We performed the first detailed photometric and spectroscopic analysis of the G-type eclipsing binary NY Boo. The radial velocity curve of NY Boo was obtained using LAMOST and SDSS spectra by the method of cross-correlation function, and the mass ratio of the binary system was derived as q=0.139. The CCF profiles of the SDSS spectra and the orbital period analysis indicate the presence of a third object. With all available eclipse times, the O-C curve was constructed. The orbital period analysis shows that in addition to the long-term decrease, there are periodic oscillations in the orbital period due to the light travel time effect of the third body. When the luminosity contribution of the third body is consistent with the CCF profile, the third body is non-coplanar to the inner pair with mass m3 = 0.31 M⊙. The TESS light curves were analyzed with the Wilson-Devinney program, and the results indicate that NY Boo is a deep and low mass ratio contact binary with a fill-out factor of f = 73%. The light curves exhibit significant asymmetry that can be well-fitted with the spot model. As the orbital period decreases, the orbital contraction causes an increase in the contact degree, and NY Boo may eventually merge due to the dynamical instability. Statistics of deep and low mass ratio contact binaries with long-term decreasing periods reveal that NY Boo is the fastest decreasing one. The fast-shrinking occurs in inner binaries with a non-coplanar third body, making NY Boo an important target for studying binary mergers.
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