Tidally Tilted Pulsations in Close Eclipsing Binaries

Recent observations with the Transiting Exoplanet Survey Satellite (TESS) have revealed a new class of pulsating star in close binary systems, in which the pulsation axis of one of the stars becomes aligned with the tidal axis of the binary (i.e., the line connecting the two stars). These systems, referred to as “tidally tilted pulsators” (TTPs), allow us to identify the pulsation modes of the star, as the observer can view the star through a range of latitudinal angles with respect to the pulsation axis. Over the past two years, there have been four tidally tilted pulsators that have been conclusively identified, and a handful more whose pulsations have been characterized as “tidally perturbed.” Three of the known TTPs are delta Scuti stars, while the fourth is a subdwarf B (sdB) star.

In this talk, we will briefly present the three delta Scuti TTPs and then focus on the recent detection of TTPs in an sdB star and the asteroseismic inferences enabled by our discovery. We found 31 independent mode frequencies, of which 27 have sidebands split by the orbital frequency or multiples thereof. We characterized the evolutionary state of this star and then modeled its oscillation modes. Due to the prevalence of g modes in the pulsation spectrum, our results show that this star is just past its helium-burning phase. This star has proven to be a valuable laboratory for asteroseismic studies, and future work on it will involve constructing three-dimensional models to study in detail mode geometries in heavily distorted stars, an area of ongoing research with few or no existing observational constraints.