Kinematic analysis and membership status of TWA22ABR

TL;DR

This study precisely measures the kinematic properties of TWA22AB to determine its membership in young stellar associations, providing valuable data for calibrating stellar evolution models.

Contribution

The paper presents new, accurate measurements of parallax, proper motion, and radial velocity for TWA22AB, clarifying its membership status and enhancing the data set for young, nearby stars.

Findings

TWA22AB is located at 17.5 parsecs from Earth.

Proper motion of TWA22AB is -175.8mas/yr in RA and -21.3mas/yr in Dec.

Radial velocity of TWA22AB is 14.8 km/s.

Abstract

TWA22 was initially regarded as a member of the TW Hydrae association (TWA). In addition to being one of the youngest (~8Myr) and nearest (~20pc) stars to Earth, TWA22 has proven to be very interesting after being resolved as a tight, very low-mass binary. This binary can serve as a very useful dynamical calibrator for pre-main sequence evolutionary models. However, its membership in the TWA has been recently questioned despite due to the lack of accurate kinematic measurements. Based on proper motion, radial velocity, and trigonometric parallax measurements, we aim here to re-analyze the membership of TWA22 to young, nearby associations. Using the ESO NTT/SUSI2 telescope, we observed TWA22AB during 5 different observing runs over 1.2 years to measure its trigonometric parallax and proper motion. This is a part of a larger project measuring trigonometric parallaxes and proper motions of most known TWA members at a sub-milliarcsec level. HARPS at the ESO 3.6m telescope was also used to measure the system's radial velocity over 2 years. We report an absolute trigonometric parallax of TWA22AB, 57.0mas, corresponding to a distance 17.5pc from Earth. Measured proper motions of TWA22AB are -175.8mas/yr in right ascension and -21.3mas/yr in declination. Finally, from HARPS measurements, we obtain a radial velocity 14.8km/s.