Uncovering hidden Kepler pulsating binaries through spectroscopic detection

Multiple star systems are ubiquitous in the universe—they are comprised of stars at every evolutionary stage and can be found in almost every astrophysical environment. Studying multiple star systems is crucial to our understanding of stellar interiors and stellar evolution and directly influences our understanding of astrophysical processes on larger physical scales. Binary star systems present a unique set of properties, such as the constraint of coevality and the ability to derive dynamical masses, which make them ideal testbeds for stellar astronomy.

As space-based photometric missions continue to revolutionize asteroseismology and call into question our understanding of stellar interiors and evolution, studying stellar pulsators in binary star systems provides the unique opportunity to test our stellar models in well-constrained systems with precise stellar parameters. Kepler and TESS have increased the sample of known pulsating binaries significantly, but the current sample suffers from observational biases which propagate into the stellar/orbital parameters of the binary sample.

To increase the sample of pulsating binaries and hopefully expand into new regions stellar/orbital parameter space, I identified 21 potential ‘hidden’ binaries from a sample of Kepler red giants. The targets appear to have signatures of solar-like and classical oscillations, but no signs of eclipse. By taking time series spectroscopic follow-up observations of these targets, I can detect orbital motion that was ‘hidden’ from photometric detection. 17 of these targets have been observed 4+ times over the last 1 ½ years using the high-resolution visible echelle spectrograph on the 3.5-meter telescope at Apache Point Observatory. Through the detection of periodic Doppler shifts in spectral lines and the derivation of radial velocities using the broadening function technique, 16 targets have been confirmed as spectroscopic binaries. This work has uncovered previously ‘hidden’ binaries, increasing the sample of pulsating binaries for study, and providing added value to Kepler data archive.