Magnetic Activity on Four Short-period Contact Binaries: V0576 Peg, KW Psc, V0873 Per, and FY Boo

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We presented new CCD photometry for two contact binaries, V724 And and QR Com, which were observed during the 2020-2022 observing seasons. By using the W-D method, the photometric solutions were deduced from new observed data and TESS ones. Their asymmetric light curves were modeled by a dark spot on the more massive component. Results indicate that the starspot may immigrate or disappear on the surface of the active component. From the TESS observations of QR Com, it is discovered that the difference between light maxima exhibits a 29.5-d oscillation, which implies the continuous evolution of spot feathers on the time-scale of several weeks. Their mass ratio and fill-out factor are q = 2.308 and f = 11.55% for V724 And, and q = 0.624 and f = 12.77% for QR Com, respectively. From the (O − C) curve, the orbital period secularly decrease at a rate of dP/dt = −1.66 × 10^{−7} d yr^{−1} for V724 And and dP/dt = −3.98 × 10^{−7} d yr^{−1} for QR Com, which was interpreted by mass transfer from the less massive component to the more massive one. With mass transferring, this kind of shallow-contact binaries, V724 And and QR Com, will evolve into the broken-contact configurations.

Section: New Photometrymentioning

confidence: 94%

“…Meanwhile, the secondaries are located above the TAMS lines. The overluminosities may be attributed to energy transfer (Zhang et al 2020;Yang et al 2022).…”

Section: Absolute Parameters and Evolutionary Statusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photometric and Spectroscopic Studies for Two Magnetic-activity Contact Binaries: V724 And and QR Com

Wang¹,

Michel²,

Yuan³

et al. 2022

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“…Long term changes of the orbital period in contact binary systems are very common phenomena. According to the investigations, the period of a contact binary is not constant in many cases (Qian 2001;Qian et al 2007;Xiao et al 2016;Yang et al 2022aYang et al , 2022bPanchal et al 2022;Gao et al 2022;Hu et al 2022;Xu et al 2022). However, there are also cases with unchanged periods, such as LQ Com (Hu et al 2022) and PZ UMa (Zhou & Soonthornthum 2019).…”

Section: Secular Period Changesmentioning

confidence: 99%

Period Investigation on Two W UMa Binaries HH UMa and V1175 Her

Chang¹,

Zhu²,

Meng³

2023

HH UMa and V1175 Her are two W UMa contact binary systems whose periods were reported as undergoing secular increase. In this paper, we improved their period analyses with a more extensive database of eclipse timings, finding that both periods show cyclic variation. The cyclic variation could be attributed to a Light Travel Time Effect (LTTE) induced by a third body. Both circular orbit and eccentric orbit cases were considered. For HH UMa, A cyclic variation with a period of around 20 yr has been detected, which may be caused by a third body with the mass larger than 0.23 M⊙. However, no parabolic variation was detected in its O-C curve, implying the balance of the mass transfer between the two components and the angular momentum loss from the binary system. As to V1175 Her, a long-term period increase superposed on a periodic oscillation was detected. The period increase at a rate of about dP/dt = 2×10−7d · yr−1 indicates the mass transfer from the less massive component to its companion. And the cyclic variation of about 7.5 yr could be caused by a hierarchical third body with a minimal mass exceeding 0.46M⊙ orbiting around the central binary. This mass is larger than that of the less massive component of the binary, which means that the secondary component was not replaced by the third body during early stellar interactions, implying it keeps original dynamical information. By removing angular momentum from the central binary system, the tertiary component has played a significant role in the formation of contact binaries.

“…Latković et al (2021) carried out a study of 700 W UMa binaries and obtained a series of statistical relations between parameters of binaries. A dozen of short-period contact binaries with magnetic activities have been observed by Long et al (2019), Zhang et al (2020a) and Yang et al (2022). They studied the dark spot immigrating on the stellar surface inferred from asymmetric light curves.…”

Section: Introductionmentioning

confidence: 99%

Light and Period Variations in Two K-type Contact Binaries: HI Leo and V523 Cas

Yang

Wang²,

Yuan³

et al. 2022

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We presented a low-precision spectrum for HI Leo, TESS data for V523 Cas, and new photometry for two K-type contact binaries. Comparing their light curves with different observing dates, we found small intrinsic variabilities, such as variable amplitudes for HI Leo and the varying heights around the second maxima for V523 Cas. By the Wilson-Devinney Code, we deduced six photometric solutions. The dark spot inV523 Cas may appear on the surface on the more massive component on BJD2458768, while it disappears on BJD 2458779. Our results indicate that two binaries are W-type shallow-contact binaries (f<10%). From the eclipse timing residuals, we found that the orbital periods may continuously increase, accompanied by one to two light-time effects due to additional bodies. Their modulated periods and semi-amplitudes are 25.8(+/-1.0)yr and 0.0066(6)d for HI Leo, 114.8(+/-2.0)yr and 0.0448(12)d, 18.89(+/-0.14)yr and 0.0025(2)d for V523 Cas, respectively. The orbital period secularly increases at a rate of dP/dt=2.86(+/-0.11)10^{-7}d/yr for HI Leo and dP/dt=3.45(+/-0.07)10^{-8}d/yr for V523 Cas, which may be attributed to mass transfer from the secondary to the primary. With mass transferring, the shallow-contact binaries, HI Leo and V523 Cas, will evolve into the broken-contact configurations.