Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-Velocity Characterization

TL;DR

This paper reports the discovery of a microlensing exoplanet toward a disk star, which is bright enough for radial velocity follow-up, enabling detailed characterization and testing of microlensing models.

Contribution

It presents the first microlensing planet with a host bright enough for radial velocity measurements, linking microlensing and RV methods for comprehensive exoplanet analysis.

Findings

Discovered a Jovian exoplanet via microlensing toward a disk star.

The host star's brightness allows for potential radial velocity follow-up.

Gaia astrometric microlensing can precisely measure system parameters.

Abstract

We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with M_p = 0.59^{+0.15}_{-0.05} M_J at a projected orbital separation r_perp = 1.4^{+0.8}_{-0.3} AU, and the host is a ~1.1 M_sun turnoff star at ~1.3 kpc. At r'~14, the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity of testing the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the ''inner-outer correlation'' inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius theta_E, but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to definitive characterization of the lens system.