The Deep and Low-Mass-Ratio Contact Binary CSS J022914.4+044340 with A Luminous Additional Companion

TL;DR

This study presents detailed photometric and spectroscopic analysis of the low-mass-ratio contact binary CSS J022914.4+044340, revealing its evolutionary stage, physical parameters, and a luminous third companion, contributing to understanding binary star evolution.

Contribution

It provides the first multi-band light curves and comprehensive physical parameters of CSS J022914.4+044340, including the detection of a luminous third body and insights into its evolutionary status.

Findings

CSS J022914.4+044340 is a deep, low mass ratio contact binary.

A luminous third companion is inferred, likely a subgiant.

The primary component has higher mass and lower metallicity than similar systems.

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 has been 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 the metallicity are determined from the spectroscopic data as T = 5855 +- 15 K, 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 M1 = 1.44 (+0.25,-0.22) solar mass, M2 = 0.29 (+0.05,-0.05) solar mass, R1 = 1.26 (+0.08,-0.06) solar radius, R2 = 0.65 (+0.03,-0.04) solar radius, L1 = 1.718 (+0.186,-0.191) solar luminosity, L2 = 0.416 (+0.039,-0.050) solar luminosity. Combined the fraction in light of the third body via the photometric solution (54%), the luminosity of the third body is estimated as 2.705 solar luminosity. The third body may be inferred as a subgiant. Thus, it is explained that why the primary component of CSS J022914.4+044340 has higher mass among the similar systems, and why its metallicity is so poor.