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

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.