KIC 3858884: a hybrid δ Scuti pulsator in a highly eccentric eclipsing binary

TLDR: In this paper, an analysis of eclipsing binaries containing non-radial pulsators is presented to combine two different and independent sources of information on the internal structure and evolutionary sta tus of the components, and the effects of tidal forces on pulsations.

Abstract: The analysis of eclipsing binaries containing non-radial pulsators allows: i) to combine two different and independent sources of information on the internal structure and evolutionary sta tus of the components, and ii) to study the effects of tidal forces on pulsations KIC 3858884 is a bright Kepler target whose light curve shows deep eclipses, complex pulsation patterns with pulsation frequencies typical ofδ Sct, and a highly eccentric orbit We present the result of th e analysis of Kepler photometry and of high resolution phaseresolved spectroscopy Spectroscopy yielded both the radial velocity curves and, after spectral disentangling, the p rimary component effective temperature and metallicity, and line-of-sight pro jected rotational velocities The Kepler light curve was analyzed with an iterative procedure devised to disentangle eclipses fro m pulsations which takes into account the visibility of the pulsating star during eclipses The search for the best set of binary parameters was performed combining the synthetic light curve models with a genetic minimization algorithm, which yielded a robust and accurate determination of the system parameters The binary components have very similar masses (188 and 186 M⊙) and effective temperatures (6800 and 6600 K), but different radii (345 and 305 R⊙) The comparison with the theoretical models evidenced a somewhat different evolutionary status of the components and the need of introducing overshooting in the models The pulsation analysis indicates a hybrid nature of the pulsating (secondary) component, the corresponding high order g-modes might be excited by an intrinsic mechanism or by tidal forces