A Gaia DR2 Confirmation that 2MASS J12074836-3900043 is a Member of the TW Hya Association

TL;DR

Using Gaia DR2 data, the study confirms 2MASS J12074836-3900043 as a genuine member of the TW Hya association and assesses the membership probability of another candidate, highlighting the importance of precise astrometric data.

Contribution

The paper provides new Gaia DR2 astrometric data that confirms membership of a young brown dwarf in TWA and refines the membership probability of another candidate.

Findings

Confirmed 2MASS J12074836-3900043 as a TWA member with a ~15 M_Jup mass.

Increased Bayesian membership probability for 2MASS J12474428-3816464.

Uncertainty remains about the true membership of the second candidate due to velocity separation.

Abstract

We use new data from Gaia DR2 to confirm that the young L1 $\gamma$ candidate member of the TW Hya association (TWA) is now a bona fide member with a model-dependent mass estimate of ~15 $M_{Jup}$. The ambiguous M9 $\gamma$ candidate member 2MASS J12474428---3816464 also gets a higher Bayesian membership probability for TWA membership as a result of Gaia DR2 data and a new radial velocity measurement, but it remains unclear whether it is a true member of TWA or if it is an unrelated young interloper, because it is separated by 4.6 km/s from the locus of TWA members in UVW space.