New low mass ratio contact binaries in the Catalina Sky Survey

Abstract

We present the identification and photometric analysis of 30 new low mass ratio (LMR) totally eclipsing contact binaries found in Catalina Sky Survey data. The LMR candidates are identified using Fourier coefficients and visual inspection. We perform a detailed scan in the parameter plane of mass-ratio (q) versus inclination (i) using Phoebe-0.31 scripter to derive the best (q, i) pair for the initial models. The relative physical parameters are determined from the final model of each system. A Monte Carlo approach was adopted to derive the parameter errors. The resulting parameters confirm the identification. The approximate absolute physical parameters of the systems are estimated based on the light curve solutions and Gaia early Data Release 3 distances. Twelve out of 30 new systems have fill-out factors $f>50{{\ \rm per\ cent}}$ and q ≤ 0.25 (deep contact LMR systems), and 8 of them, to within errors, are extreme LMR deep systems with q ≤ 0.1. We discuss the evolutionary status of the 30 LMR systems in comparison with the most updated catalog of LMR systems from the literature. The scenario of the LMR systems as pre-merger candidates forming fast rotating stars is investigated for all systems, new and old, based both on Hut’s stability criteria and critical instability mass ratio (qinst) relation. CSS$\_$J075848.2+125656, with q/qinst = 1.23 ± 0.23, and CSS$\_$J093010.1-021624, with q/qinst = 1.25 ± 0.23, can be considered as merger candidates.

The study of eleven contact binaries with mass ratios less than 0.1

“…According to the photometric solutions, we knew that the fill-out factors of eleven targets are between 18.9% and 94.3%, which showed that our contact binaries have shallow, medium and deep contact systems. Therefore, it proved the conclusion proposed by Christopoulou et al (2022). Table 9 listed the physical parameters obtained by us and those determined by Sun et al (2020).…”

“…Among the eleven systems, J164000 has the largest temperature difference between the two components, which is 563K. Christopoulou et al (2022) proposed a conclusion that contact binaries with low-mass ratios can present deep or medium or shallow degree of contact. Qian et al (2005a) defined that the contact binaries whose degree of contact exceeds 50% as deep contact binaries.We defined medium and shallow contact configuration as that the fill-out factors are between 25% and 50%, and less than 25%.…”

Three Ultra-short-period Contact Eclipsing Binary Systems Mined from Massive Astronomical Surveys

“…These include semimajor axis-period relations (Şenavcı et al 2016), total mass-period relations (Dimitrov & Kjurkchieva 2015), main-sequence approximation of the massive components, mass-luminosity relations (Sun et al 2020;Ren et al 2021), period-mass ratio relations (Schuh et al 2009), etc. We adopted the empirical luminosity-mass relation for the primary mass from Christopoulou et al (2022):…”

On the true nature of the contact binary CRTS J192848.7‐404555

“…Analysis of survey photometry in the detection of interesting, particularly low mass ratio contact binary systems has received considerable attention recently (Christopoulou et al 2022;Devarapalli et al 2020;Wadhwa et al 2022b Her (Caton et al 2019). In both cases, the survey analysis over-estimated the mass ratio compared to spectroscopic mass ratio in the case of CN Hyi and dedicated ground-based observations in the case of V1187 Her.…”

“…Lucy (1968) suggested that the discrepancy in the brightness and size of the secondaries was due to the transfer of energy from the primary to the secondary within the common envelope. A number of authors have explored the relationship between the mass ratio and luminosity and the transfer of energy between the components (Csizmadia & Klagyivik 2004;Wang 1994) with general agreement that energy transfer is a function of both the mass ratio and luminosity ratio.…”