Looking for astrometric signals below 20 m/s: A Jupiter-mass planet signature in $\epsilon$ Eri

TL;DR

This study combines ground-based and space-based astrometry over 25 years to detect a Jupiter-mass exoplanet around $ ext{ε}$ Eri, confirming its existence with high confidence through proper motion analysis.

Contribution

It demonstrates the effectiveness of combining multiple astrometric datasets to detect long-period exoplanets below 20 m/s signals, confirming a planet around $ ext{ε}$ Eri.

Findings

Detection of a long-period exoplanet orbiting $ ext{ε}$ Eri.

Confirmation of the planet's existence with high statistical confidence.

Astrometric signals consistent with previous radial velocity hints.

Abstract

The USNO ground-based astrometric program URAT-Bright in combination with the Hipparcos mission epoch astrometry provides precise proper motions of a thousand bright stars in the southern hemisphere on a time basis of about 25 years. Small but statistically significant differences between these proper motions and Gaia EDR3 data can reveal long-period exoplanets similar to Jupiter in the nearest star systems. The presence of such a planet orbiting the magnetically active dwarf $\epsilon$ Eri is confirmed from both URAT--Hipparcos--EDR3 data and Hipparcos--EDR3 data with a corresponding projected velocity of $(+5,+8)$ and $(+6,+13)$ m s$^{-1}$, respectively. These signals are formally significant at a 0.989 and 1.0 confidence. We conclude that the newest astrometric results confirm the existence of a long-period exoplanet orbiting $\epsilon$ Eri, which was marginally detected from precision radial velocity measurements some 20 years ago.