Vol 21, No 7

The deep and low-mass-ratio contact binary CSS J022914.4+044340 with a luminous additional companion

Liang Liu, Xu-Zhi Li


Abstract The first B-, V -, Rc- and Ic-band light curves of CSS J022914.4+044340 are presented and analyzed. It is found that CSS J022914.4+044340 is a low mass ratio (0.198± 0.005) deep (63.7± 7.9%) contact binary, indicating that it is already at the end evolutionary stage of tidally-locked evolution via magnetized wind. Because of the totally eclipsing character, the photometric solutions are reliable. The temperature and metallicity are determined from the spectroscopic data as T = 5855 ± 15K and [Fe/H] = −0.842 ± 0.031, respectively. Based on the parallax of Gaia EDR3, the physical parameters of CSS J022914.4+044340 are estimated as \(M_1= 1.44^{+0.25}_{-0.22}M_{\odot}, M_2 = 0.29^{+0.05}_{-0.05}M_{\odot}, R_1 =1.26^{+0.08}_{-0.06} R_{\odot}, R_2 = 0.65^{+0.03}_{-0.04} R_{\odot}, L_1 = 1.718^{+0.186}_{-0.191} L_{\odot}\) and \(L_2 = 0.416^{+0.039}_{-0.050}L_{\odot}\). Combining the fraction of light from the third body via the photometric solution (54%), the luminosity of the third body is estimated as 2.705 L⊙. The third body may be inferred to be a subgiant. Thus, why the primary component of CSS J022914.4+044340 has higher mass compared to similar systems is explained, as well as why its metallicity is so poor.


Keywords binaries : eclipsing—binaries : close—stars: individuals (CSS J022914.4+044340)—stars: evolution

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