2017/12/07 by Liang Liu, Linsheng Liu, Shengbang Qian +3
Earth and Planetary Sciences · Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Binary number #Binary star #Common envelope #Contact binary #Convection #High-pressure geophysics and materials #Mass ratio #Mass transfer #Mechanics #Merge (version control) #Orbital period #Oscillation (cell signaling) #Physics #Stars #Stellar, planetary, and galactic studies #Term (time) #Thermal #Thermodynamics #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stx3138
8 pages, 4 figures, accepted by MNRAS
openalex publication_date 2017/12/07 · arxiv created 2017/12/13 · arxiv updated 2017/12/14 · openalex created_date 2017/12/22 · openalex updated_date 2026/08/05
W UMa-type contact binaries belong to close binary systems whose components exactly overflow their Roche lobes and share a common convective envelope (CCE). In the last twenty years, the long-term variations of their orbital periods have been thought to depend on several mechanisms. Now, we suggest a new mechanism: CCE-dominated mechanism. The CCE-dominated mechanism is found based on our numerical result, especially at high mass ratios, that the orbital periods (P) of contact binaries change very much with their fill-out factors (f). Because f is taken as a measurement of the thickness of CCE, the physical cause for the variation of P is a mass transfer between CCE and components. Further, an f-dominated simplification model for this mechanism is introduced. According to it, P may change in a long-term oscillation way with a similar time scale of the thermal modulation, meanwhile q is decreasing slowly till the two components merge. It could be also applied to explain the presence of extremely short period, high mass ratio and deep contact binaries. Moreover, the CCE-dominated mechanism should always work due to mass transfer and mass loss both occurring via CCE. Therefor, the effect of CCE on the variations of orbital periods may have been underestimated before.