RR Lyrae Stars as Accelerometers and their Post-Engulfment Companions

In recent years, there has been an effort to directly measure accelerations from periodic astronomical sources such as pulsars and eclipsing binaries; these accelerations provide constraints for the Milky Way’s dark matter distribution. We explore the feasibility of using pulsating variable stars, particularly RR Lyrae stars, as probes of the Galactic acceleration field. With the precision of existing datasets, it should be possible to measure Galactic accelerations using RRLs with a decade baseline. Additionally, we find evidence for 7 short-period brown dwarf companions around Kepler RR Lyrae stars from the accelerations these companions impart on their host stars. 6 of the 7 candidate companions are located within the radius that an RR Lyrae star would have had on the giant branch, indicating the companions either survived engulfment or formed after their host stars moved to the horizontal branch. Many of these companions are in orbital resonances, and tidal deformations of the host star and/or the companion(s) may play an important role in the long-term stability of these systems.