TV Mon – post-mass transfer Algol-type binary with <i>δ</i> Scuti pulsations in primary component

ABSTRACT We present a study of the detached eclipsing binary TV Mon using spectra from the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) medium-resolution survey, ASAS-SN (All Sky Automated Survey for SuperNovae), and CoRoT (Convection, Rotation and planetary Transits) photometry. We apply multiple-epochs spectral fitting to derive radial velocities and spectral parameters. The analysis of eclipses in CoRoT data shows the relative sizes of the stellar components and almost edge-on circular orbit. Combining the spectral and photometrical solutions we estimate masses and radii of the components: $M_{\rm A,B}=2.063\pm 0.033({\rm stat.})\pm 0.095({\rm syst.}), \ 0.218\pm 0.004({\rm stat.})\pm 0.018({\rm syst.}) \, \mathrm{ M}_\odot$, $R_{\rm A,B}=2.394\pm 0.014, \ 2.860\pm 0.016 \, \mathrm{ R}_\odot$. Spectral energy distribution analysis and Gaia parallax allow us to get an estimation of temperatures ${T_{\rm eff}}_{\rm A,B}=7624^{+194}_{-174}, \ 5184^{+130}_{-123} \, \mathrm{ K}$ and distance $d=907\pm 11 \, \mathrm{ pc}$. We identify three $\delta$ Scuti-type pulsation frequencies in the primary component, while we also suspect TV Mon having a spot activity in the secondary component. This system experienced intensive mass transfer and mass ratio reversal in the past, but currently shows no signs of mass transfer in the spectra. The low-mass component will lose its outer envelope and shrink to the helium white dwarf, the mass and orbital period of which are in good agreement with evolutionary model predictions.