On the identification of wide binaries in the Kepler field

We perform a search for wide binaries in the Kepler field with the prospect of providing new constraints for gyrochronology. First, we construct our base catalogue by compiling astrometry for the stars observed by Kepler, and supplement it with parallaxes, radial velocities (RVs), and metallicities. We then mine our base catalogue for wide binary candidates by matching the stars' proper motions, as well as parallaxes, RVs, and metallicities, if available. We mitigate the presence of chance alignments among our candidates by performing a comprehensive data-based contamination analysis in the proper motion versus angular separation phase space. Our final sample contains 55 binary candidates. A cross-match of our pairs with the Second Data Release (DR2) from Gaia validates our candidates and confirms the reliability of our search method, particularly for ϖ ≳ 2 mas. Due to the implicit Kepler selection function and image scale per pixel, our binary search is incomplete for angular separations of Δθ ≲ 20″. We cross-match our candidates with rotation period and asteroseismic ages catalogues, and find that our binary candidates do not follow a simple period-colour relation, in agreement with previous studies. Two pairs have an age estimate for one component star and rotation period for its companion, positioning them as potentially new gyrochronology constraints at old ages. This is the first study that uses RVs and metallicities as criteria, rather than as a confirmation, in a binary search.