Forward modeling the orbits of companions to pulsating stars from their light travel time variations (2003.02379v1)

Abstract: Mutual gravitation between a pulsating star and an orbital companion leads to a time-dependent variation in path length for starlight traveling to Earth. These variations can be used for coherently pulsating stars, such as the {\delta} Scuti variables, to constrain the masses and orbits of their companions. Observing these variations for {\delta} Scuti stars has previously relied on subdividing the light curve and measuring the average pulsation phase in equally sized subdivisions, which leads to under-sampling near periapsis. We introduce a new approach that simultaneously forward-models each sample in the light curve and show that this method improves upon current sensitivity limits - especially in the case of highly eccentric and short-period binaries. We find that this approach is sensitive enough to observe Jupiter mass planets around {\delta} Scuti stars under ideal conditions, and use gravity-mode pulsations in the subdwarf B star KIC 7668647 to detect its companion without radial velocity data. We further provide robust detection limits as a function of the SNR of the pulsation mode and determine that the minimum detectable light travel time amplitude for a typical Kepler {\delta} Scuti is around 2 s. This new method significantly enhances the application of light travel time variations to detecting short period binaries with pulsating components, and pulsating A-type exoplanet host stars, especially as a tool for eliminating false positives.