Hybrid Pulsations and Tidal Splitting detected in the Kepler Eclipsing and Spotted Binary System KIC 6048106

Abstract

We present a new asteroseismic analysis of KIC~6048106, a \textit{Kepler} Algol-type eclipsing binary star in a circularized orbit with $P_\rm{orb}$=1.559361$\pm$0.000036~d. Based on a physical model for the binary and its corresponding set of fundamental parameters, ($T_\rm{eff}=7033\pm187~K, ~M_\rm{1}=1.55\pm0.11M_{\odot}$ and $T_\rm{eff}=4522\pm103~K,~M_\rm{2}=0.33\pm0.07M_{\odot}$, respectively for the primary and the secondary component), we obtained the residual light curve after removal of the full binary model, including a 290-day activity cycle for the secondary component (Samadi Gh. et al.\,2018). In this work, we used the method of Fourier analysis of the residual light curve in combination with least squares optimization for the frequency analysis. We detected seven dominant, independent gravity ($g$) modes as well as 34 low-amplitude acoustic ($p$) modes. The $g$ modes in the range $1.96-2.85$ d$^{-1}$ have a mean spacing of $\Delta\Pi_\rm{mean}=1517.92\pm131.54$~s. Though of much lower amplitude, additional significant frequencies were detected in the intervals $7.49-15.2$ d$^{-1}$ and $19-22.5$ d$^{-1}$ (i.e. in the $p$ mode region), with corresponding dominant modes $\nu_\rm{max_\rm{1}}=11.745\pm0.001$ d$^{-1}$ and $\nu_\rm{max_\rm{2}}=20.960\pm0.002$ d$^{-1}$. From its position in the H-R diagram, we conclude that the primary component is the source of the detected hybrid pulsations. Consequently, the pulsation constants, Q, of the high frequencies cover the range $0.028-0.064$~d. Furthermore, $\nu_\rm{43} $ (19.037$\pm$0.002 d$^{-1}$) might correspond to the fundamental radial mode (Q = 0.033$\pm$0.007 d). The other frequencies in the range $19-22.5$ d$^{-1}$ could be radial or non-radial overtone modes. Moreover, the low-amplitude $p$ modes show an equidistant splitting by $f_\rm{orb}$, which we interpret as tidal splitting following theoretical predictions.