IDENTIFICATION OF TESS (TOI) CANDIDATES WITH ASTROMETRIC EVIDENCE OF AN UNREPORTED STELLAR COMPANION USING GAIA DR3 ASTROMETRY

Unresolved stellar binaries systematically contaminate exoplanet candidate catalogs: an undetected companion dilutes the observed transit depth, producing an underestimated planetary radius or, in extreme cases, a false positive caused by an eclipsing binary. Here, a systematic screening of unconfirmed TESS Objects of Interest (TOIs, tfopwg_disp = PC) against Gaia DR3 astrometry is presented, using the Renormalised Unit Weight Error (RUWE) and the fraction of point-source profiles showing a second light peak (ipd_frac_multi_peak) as tracers of unresolved binarity. Out of a sample of 1000 TOIs, 15 candidates survived a chain of quality-control filters (magnitude-based cross-match verification, RUWE > 1.4, absence of a binary solution already cataloged by Gaia). For two of them, a real physical companion was confirmed via shared proper motion and, in a subsequent verification step, via mutually consistent Gaia parallaxes (∆ϖ < 1.5σ in both cases), allowing us to compute the photometric dilution correction on the published planetary radius: TOI-3038.01 goes from 24.2 to 25.5R⊕ (+5.5%), and a ∼34% correction is predicted for TOI-5046.01 once its radius is published. In addition, 8 candidates with very high RUWE (3.1–51.6) lack a resolved neighboring Gaia source within 4′′, suggesting companions at sub-arcsecond separations still unconfirmed by high-resolution imaging. The method constitutes a computationally inexpensive filter, readily scalable to the full TOI catalog, for prioritizing candidates for speckle/adaptive-optics follow-up.