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arXiv · 2411.12132

Detection of the lowest mass ratio contact binary in the universe: TYC 3801-1529-1

Kai Li·Xiang Gao·Di-Fu Guo·Dong-Yang Gao·Xu Chen·Li-Heng Wang·Yu-Xin Xin·Yu-Xin Han·Chun-Hwey Kim·Min-Ji Jeong
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Abstract

This paper presents the first analysis of the contact binary TYC 3801-1529-1. We observed four sets of multiple bands complete light curves and one set of radial velocity curve of the primary component. Based on a simultaneous investigation of our observed and TESS light curves and the radial velocity curve, we found that TYC 3801-1529-1 is an extremely low-mass-ratio, medium contact binary with $q=0.0356$, with the contribution of the third light at a level of about 10\%. Its mass ratio is lower than V1187 Her, making TYC 3801-1529-1 the lowest mass-ratio contact binary ever found in the universe. The light curves observed in 2022 are asymmetric, which is aptly explained by a hot spot on the primary component. A 16-year eclipse timings analysis indicates a secular increase orbital period with a rate of dp/dt$=7.96(\pm0.35)\times10^{-7}$ d yr$^{-1}$. We studied the stability of this target and identified that not only the value of $J_{spin}/J_{orb}$, but also the mass ratio surpass the unstable boundary. Hence, TYC 3801-1529-1 presents a challenge to theoretical research and ought to be considered a progenitor of a contact binary merger.

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Kai Li, Xiang Gao, Di-Fu Guo, Dong-Yang Gao, Xu Chen, Li-Heng Wang, Yu-Xin Xin, Yu-Xin Han, Chun-Hwey Kim, Min-Ji Jeong. 2024-11-19. Detection of the lowest mass ratio contact binary in the universe: TYC 3801-1529-1. https://doi.org/10.1051/0004-6361%2F202451947

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