KIC 7914906: An eclipsing heartbeat star with tidally excited oscillations and gamma Doradus/delta Scuti hybrid pulsations

Abstract

We present the eclipsing heartbeat star KIC 9704906 with tidally excited oscillations (TEOs) and gamma Doradus/delta Scuti hybrid pulsations. The derived parameters show that it has an orbital period of $P = 8.7529108(1)$ d, a high eccentricity of $e = 0.467(3)$, and a high inclination of $i = 78.^{\!\!\!\circ }81(6)$. The mass ratio $q = 0.981(5)$ and relative radii (radius divided by the semi-major axis) $r_1 = 0.0639(2)$ and $r_2 = 0.0715(4)$ indicate that the secondary component has a smaller mass and a larger radius, and may have evolved off the main sequence. The eight derived TEO candidates, $n = 3$, 4, 5, 6, 7, 12, 40, and 44 harmonics, are consistent with or close to the dominant spherical harmonic $l=2$, $m=0$, or $\pm 2$, assuming that the spin and orbital axes are aligned, and the pulsations are adiabatic and standing waves. We also identify eight independent frequency candidates, but one of them, ${f_{7}}$, is more like a modulation of a quasi-periodic signal and the orbits. According to the g-mode frequencies, we find that the rotation period of one component is 11.52(29) d. Although the masses and radii cannot be further constrained due to the lack of sufficient high-precision spectra, fascinating phenomena in the Fourier spectra are evident and valuable in this system.