Searching for substellar companion candidates with Gaia. III. Search for companions to members of young associations

TL;DR

This paper evaluates Gaia's astrometric capabilities for detecting and characterizing substellar companions, combining Gaia data with direct imaging and RV measurements, and reports new detections and confirmations of exoplanets and brown dwarfs.

Contribution

It introduces GaiaPMEX, a new tool for analyzing Gaia data to detect and characterize substellar companions, and applies it to identify and confirm several exoplanets and brown dwarfs.

Findings

Detection of a new giant planet around G80-21

Confirmation of substellar companions to AB Pic and HD 14082 B

Identification of 9 planetary mass candidates

Abstract

Absolute astrometry with Gaia is expected to detect and characterize the orbits of thousands of exoplanets in the coming years. A tool, GaiaPMEX, was recently developed to characterize multiple systems based on Gaia-only data, and, when possible, the Gaia-Hipparcos proper motion anomaly. We compare the detection capabilities of absolute astrometry and spectroscopy (RV), and to detect and characterize planetary-mass companions, combining the astrometric data with direct imaging and RV data. For companion masses possibly in the planetary range, we use direct imaging and when possible, RV data as well, to further constrain their nature and orbital properties. For each target, a diagnosis on its binarity based on absolute astrometry is given. When no binary is detected, we provides detection limits in the (sma, mass) space. We identify several companions with possible masses down to the brown dwarfs (BD; 50+) or planetary masses (13). We detect a new giant planet at less than 1-2 au from the M-type star G80-21. For AB Pic and HD 14082 B, we confirm the presence of substellar companions, and provide robust solutions for their mass and orbital properties. We further identify 9 planetary mass companions candidates. Finally, a detailed treatment of noises in Gaia astrometric measurements shows that there are no evidence at a 2-sigma level of two exoplanet detections previously announced. Combining GaiaPMEX and RV data is therefore perfectly adaptIn the 0.5 to 5 au domain, GaiaPMEX has an excellent sensitivity to BDs, and a good sensitivity to planetary mass planets for this sample.