The detached-binary channel for the formation of contact binaries

Abstract

The detached-binary channel is an important channel for the formation of contact binaries, according to which a detached binary might evolve into contact by evolutionary expansion of the components, or angular momentum loss through the effect of magnetic braking (MB). We have carried out a detailed binary population synthesis (BPS) study of this channel, and obtained the parameter regions for detached binaries to evolve into contact. Combining the observations from the $\text{Kepler}$ satellite with our results, we found that the ratio of the birth rate of the progenitors of contact binaries to that of contact binaries is greater than about 1.2. This suggests that for the detached-binary channel, the progenitors can be sufficient to produce observed contact binaries. In this channel, we find that the distribution of orbital period for contact binaries has a peak at about 0.25 days and a tail extending to longer periods, and the formation timescale of contact binaries has a large range from $\sim 1$\,Myr to 15\,Gyr. These results show that the detached-binary channel could explain satisfactorily the main observational characteristics of contact binaries, in particular the distribution of orbital period shown by the $\text{Kepler}$ observations and the existence of very young contact binaries.

23 pages, 11 figures, accepted for publication in MNRAS

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• Contribution of primordial binary evolution to the two blue-straggler sequences in globular cluster M30
• Case AD, AR, and AS binary evolution and their possible connections with W UMa binaries
• Three Ultra-short Period Contact Eclipsing Binary Systems Mined from Massive Astronomical Surveys
• Stellar activity and planetary atmosphere evolution in tight binary star systems
• Investigating stellar variability in the open cluster region NGC 381
• Photometric analysis and evolutionary stages of the contact binary V2790 Ori
• Unveiling Bifurcated Blue Straggler Sequences in NGC 2173: Insights from Binary Evolution
• A Unique Low-Mass Ratio Contact Eclipsing Binary System under the Period Cut-Off
• BM UMa: a middle shallow contact binary at pre-transition stage of evolution from W-type to A-type