Upper Limits on Stellar Companions to the Kepler-34 and Kepler-35 Systems

Abstract We obtained new spectra of Kepler-34 and Kepler-35 with Keck-HIRES—nearly a decade after these systems were originally characterized with this spectrograph and other instruments—to search for radial velocity (RV) trends from a potential third stellar-mass companion at long periods. For Kepler-34, we rule out coplanar stellar masses as low as 0.12 M ⊙ at an orbital period of ≲52 yr. For Kepler-35, we rule out stellar masses of 0.13 M ⊙ at orbital periods of ≲55 yr. Highly stable, extreme precision RV instruments, as well as improved methodologies in characterizing double-lined spectroscopic binaries that come with these new instruments, will provide an opportunity to push these mass limits lower in the future.