Updated pulsation period relations of γ Dor-type stars in eclipsing binaries: the case of KIC 2557430

Abstract

We employ optical spectroscopy and Kepler photometry to derive the physical properties and pulsational characteristics of the detached system KIC 2557430. We find that the system is formed by F-type components. Combining results from the analysis of spectroscopic data and Kepler photometry, we calculate masses and radii of the primary and the secondary components as M₁ = 1.69 ± 0.03 M_⊙, M₂ = 1.35 ± 0.02 M_⊙ and R₁ = 1.88 ± 0.02 R_⊙, R₂ = 1.23 ± 0.03 R_⊙, respectively. Position of the primary component in the HR diagram is in the region of γ Doradus-type pulsators and the residuals from light curve modelling exhibit additional light variation with a dominant period of ∼0.5 d^-1. These are clear evidence of the γ Doradus-type pulsations on the primary component. Focusing on the γ Dor primaries, with their currently known numbers in eclipsing binaries to compare against, we probe the role binary stars might play, to understand the nature of γ Dor-type pulsations.