Ultracool dwarfs in Gaia DR3

TL;DR

This study utilizes Gaia DR3 data to characterize ultracool dwarfs, revealing their distribution, binary systems, variability, and association memberships, thereby enhancing understanding of the faint end of the Main Sequence.

Contribution

The paper provides a comprehensive analysis of Gaia DR3 ultracool dwarfs, including their properties, binary systems, variability, and association memberships, which is novel in leveraging Gaia data for such detailed characterization.

Findings

Detected 57 young, kinematically homogeneous groups.

Identified 1109 variable ultracool dwarfs, 728 in star forming regions.

Most binary UCDs belong to the Milky Way's thin and thick disks.

Abstract

Aims. In this work we use the Gaia DR3 set of ultracool dwarf candidates and complement the Gaia spectrophotometry with additional photometry in order to characterise its global properties. This includes the inference of the distances, their locus in the Gaia colour-absolute magnitude diagram and the (biased through selection) luminosity function in the faint end of the Main Sequence. We study the overall changes in the Gaia RP spectra as a function of spectral type. We study the UCDs in binary systems, attempt to identify low-mass members of nearby young associations, star forming regions and clusters, and analyse their variability properties. Results. We detect 57 young, kinematically homogeneous groups some of which are identified as well known star forming regions, associations and clusters of different ages. We find that the primary members of 880 binary systems with a UCD belong mainly to the thin and thick disk components of the Milky Way. We identify 1109 variable UCDs using the variability tables in the Gaia archive, 728 of which belong to the star forming regions defined by HMAC. We define two groups of variable UCDs with extreme bright or faint outliers. Conclusions. The set of sources identified as UCDs in the Gaia archive contains a wealth of information that will require focused follow-up studies and observations. It will help to advance our understanding of the nature of the faint end of the Main Sequence and the stellar/substellar transition.