Photometric analysis of 40 low mass-ratio contact binary systems in the Catalina Sky Survey

¹ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, PR China
² University of Chinese Academy of Sciences, Beijing 100049, PR China
³ Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PO Box 110, 650216 Kunming, PR China
⁴ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
⁵ College of Physics and Electronic Engineering, Xingtai University, Xingtai 054001, PR China

^★ Corresponding author; dingxu409@163.com

Received: 26 August 2024
Accepted: 20 November 2024

Abstract

Low mass-ratio contact binary systems are a fascinating class of eclipsing binaries; they are widely regarded as the potential progenitors of stellar mergers. For this study we analyzed 40 newly discovered low mass-ratio totally eclipsing contact binary systems identified from the Catalina Sky Survey data. The relative parameters for these systems were inferred using a neural network model combined with a Bayesian inference-based Hamiltonian Monte Carlo (HMC) algorithm, with uncertainties estimated from the posterior distributions generated by the HMC algorithm. The absolute parameters were then calculated using these relative parameters, along with distances and temperatures provided by Gaia Data Release 3. Among the 40 systems, 24 are deep low mass-ratio overcontact binaries, characterized by fill-out factors of 0.5 or higher and mass ratios of 0.25 or lower. Notably, two systems, CSS_J071952.5+243224 and CSS_J155519.0+135855, have mass ratios below 0.1, specifically 0.094 ± 0.006 and 0.086 ± 0.004, respectively. Furthermore, we compared the parameters obtained in this study with those from 39 low mass-ratio contact binary systems identified in previous research, finding that the estimated parameters are largely consistent. Finally, to evaluate the evolutionary status of the 40 systems, we calculated the ratio of spin angular momentum to orbital angular momentum for each and found that all are currently in a relatively stable evolutionary phase.