The effect of tides on near-core rotation: analysis of 35 Kepler γ Doradus stars in eclipsing and spectroscopic binaries. Issue 4 (6th August 2020)

• Record Type: Journal Article
• Authors: Li, Gang; Guo, Zhao; Fuller, Jim; Bedding, Timothy R; Murphy, Simon J; Colman, Isabel L; Hey, Daniel R
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 4(2020)
• Page Start: 4363
• Page End: 4375
• Publication Date: 2020-08-06
• Subjects: binaries: eclipsing -- stars: interiors -- stars: oscillations -- stars: rotation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2266
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We systematically searched for gravity- and Rossby-mode period spacing patterns in Kepler eclipsing binaries with γ Doradus pulsators. These stars provide an excellent opportunity to test the theory of tidal synchronization and angular momentum transport in F- and A-type stars. We discovered 35 systems that show clear patterns, including the spectroscopic binary KIC 10080943. Combined with 45 non-eclipsing binaries with γ Dor components that have been found using pulsation timing, we measured their near-core rotation rates and asymptotic period spacings. We find that many stars are tidally locked if the orbital periods are shorter than 10 d, in which the near-core rotation periods given by the traditional approximation of rotation are consistent with the orbital period. Compared to the single stars, γ Dor stars in binaries tend to have slower near-core rotation rates, likely a consequence of tidal spin-down. We also find three stars that have extremely slow near-core rotation rates. To explain these, we hypothesize that unstable tidally excited oscillations can transfer angular momentum from the star to the orbit, and slow the star below synchronism, a process we refer to as 'inverse tides'.