Vetting the Lobster Diagram: Searching for Unseen Companions in Wide Binaries using NASA Space Exoplanet Missions

Abstract

Over the past decade, the number of known wide binary systems has exponentially expanded thanks to the release of data from the Gaia Mission. Some of these wide binary systems are actually higherorder multiples, where one of the components is an unresolved binary itself. One way to search for these systems is by identifying overluminous components in the systems. In this study, we examine 4947 K+K wide binary pairs from the SUPERWIDE catalog and quantify the relative color and luminosity of the components to find evidence for additional, unresolved companions. The method is best illustrated in a graph we call the "Lobster" diagram. To confirm that the identified overluminous components are close binary systems, we cross-match our wide binaries with the TESS, K2 and Kepler archives and search for the signs of eclipses and fast stellar rotation modulation in the light curves. We find that 78.9% ± 20.7% of the wide binaries which contain an eclipsing system are identified to be overluminous in the "Lobster Diagram" and 73.5% ± 12.4% of the wide binaries which contain a component showing fast rotation (P < 5) days also show an overluminous component. From these results, we calculate a revised lower limit on the higher-order multiplicity fraction for K+K wide binaries of 40.0% ± 1.6%. We also examine the higher-order multiplicity fraction as a function of projected physical separation and metallicity. The fraction is unusually constant as a function of projected physical separation while we see no statistically significant evidence that the fraction varies with metallicity.

15 000 ellipsoidal binary candidates in TESS: Orbital periods, binary fraction, and tertiary companions

“…A sample of 392 resolved triple systems was also selected from Gaia by Tokovinin (2022). Hartman et al (2022) examined a sample of resolved K+K binaries, and found at least 40 per cent to be hierarchical triple systems with an unresolved inner binary.…”