Looking for astrometric signals below 20 m/s: A candidate exo-Jupiter in $δ$ Pav

Abstract

We use a combination of Hipparcos space mission data with the USNO dedicated ground-based astrometric program URAT-Bright designed to complement and verify Gaia results for the brightest stars in the south to estimate the small perturbations of observed proper motions caused by exoplanets. One of the 1423 bright stars in the program, δ Pav, stands out with a small proper motion difference between our long-term estimate and Gaia EDR3 value, which corresponds to a projected velocity of (−17, +13) m s −1 . This difference is significant at a 0.994 confidence in the RA component, owing to the proximity of the star and the impressive precision of proper motions. The effect is confirmed by a comparison of long-term EDR3-Hipparcos and short-term Gaia EDR3 proper motions at a smaller velocity, but with formally absolute confidence. We surmise that the close Solar analog δ Pav harbors a long-period exoplanet similar to Jupiter.