Tidally perturbed pulsations in the pre-main sequence delta Scuti binary RS Cha
We present an in-depth analysis of TESS observations of the pre-main sequence \delta Scuti binary RS Cha. RS Cha is an eclipsing binary system with well known stellar parameters that is synchronised and circularised. In a such a system, the equilibrium tide is expected to perturb the self-excited pulsation modes.
We used PHOEBE to remove the eclipsing binary signal from the TESS light curve to model the residuals with superposition of linear modes. Our investigation of the pulsations uncover mulitplets split by (twice) the orbital frequencies. We use the theory of tidally perturbed modes to identify the pulsation modes and verify previous spectroscopic mode identification for a prominent l=2 or l=3 mode.
Our results suggest that RS Cha is an ideal candidate to test the theory of tidally perturbed modes within the framework of asteroseismic modelling.
Furthermore, it is the first pre-main sequence object showing tidal effects on its pulsation spectrum. As such, RS Cha will be a keystone in the future of pre-main sequence asteroseismology.