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We reported new spectroscopy and photometry for four short-period binaries, which were acquired by several small telescopes in China from 2020 to 2022. From new spectrum and Large Sky Area Multiobject Fiber Spectroscopic Telescope data, we determined their spectral types of G8V for PZ UMa, G7 for MM Com, and V0685 Peg and G3 for V1055 Her. When compared to the Transiting Exoplanet Survey Satellite (TESS) light curve (LC) with a 2-min cadence, the difference between two light maxima for V1055 Her displays a 29.7-d oscillation. Utilizing the Wilson–Devinney program, we deduced 10 photometric solutions from our new and TESS data. Four binaries are W-type ones with variable O'Connell effects. For LC2022.1 (MM Com) and LC2022.9 (V1055 Her), Δmmax=Max.I–Max.II is as large as |$15{{\ \rm per\ cent}}$| of variable light amplitude, which may be attributed to the spot's migration and evolution. From the mass-luminosity diagram, the more massive components aref somewhat evolved main-sequence stars, whereas the less massive ones are overluminous as a result of energy exchange. Based on all eclipse timing residuals, the orbital period variations are preferably described by the light-travel time effects via the presence of additional companions. Their modulation periods range from 10 to 20 yr for four binaries, corresponding the companion's mass ranging from M 3 = 0.11 to 0.34 M⊙. Therefore, four solar-type short-period contact binaries (i.e. MM Com, PZ UMa, V0685 Peg, and V1055 Her) may be triple stellar systems. [ABSTRACT FROM AUTHOR]

Abstract: We present new photometry for CE Leo and V366 Cas, performed using three small telescopes in China from 2008 December to 2012 March. Using the updated Wilson–Devinney program, the photometric solutions of two binaries were deduced from new BVR light curves. Their photometric mass ratios and geometric fill-out factors are and ) for CE Leo, and for V366 Cas, respectively. By analyzing the curves, it is found that their orbital periods show a long-time increase with a light-time orbit due to a third body. The periods of the tertiary components are for CE Leo and for V366 Cas, respectively. With the existence of addition companion, those two binaries appear to be triple systems. The period increase rates are for CE Leo and for V366 Cas, respectively. This kind of period increase may be interpreted by the conservative mass transfer from the secondary component to the primary one. With periods increasing, CE Leo and V366 Cas will evolve into broken-contact configurations as predicted by the thermal relaxation oscillation theory. [Copyright &y& Elsevier]

We present CCD photometric monitoring of the classic nova QZ Aurigae (Nova Aur 1964) since 2008 with the 2.4-m telescope at Lijiang station of Yunnan Astronomical Observatory in China, as well as the 2.16-m telescope and the 85-cm telescope at Xionglong station of the National Astronomical Observatory in China. By utilizing eight new eclipse timings and the data from the last literature, published almost 20 years ago, we construct the O − C diagram of this system to analyze the orbital period variation. We find no evidence of long-term orbital period variations in QZ Aur. Moreover, the light curves showing the main eclipse process of the white dwarf suggest the presence of a bright spot component and a disk, as commonly found in nova-like variables. This may reveal high mass accretion and high mass transfer in this system. However, even high mass transfer rates from the donor are inconsistent with our result of no period variations, unless the mass ratio is almost equal to 1. Hence, the observed results here possibly support that the mass of the primary white dwarf is extremely close to that of the donor star in the eclipsing binary QZ Aur. [ABSTRACT FROM PUBLISHER]