The young, tight and low mass binary TWA22AB: a new calibrator for evolutionary models ? Orbit, spectral types and temperatures determination

TL;DR

This study characterizes the binary system TWA22AB, providing dynamical mass, spectral types, and temperatures, and evaluates its role as a calibrator for young, low-mass evolutionary models, questioning existing model predictions.

Contribution

First dynamical mass measurement of TWA22AB, offering new data to test and refine models of young, low-mass stellar evolution.

Findings

Total mass of 220 ± 21 MJup for TWA22AB.

Effective temperatures around 2900 K for both components.

Potential underestimation of model-predicted masses near the substellar boundary.

Abstract

Tight binaries discovered in young, nearby associations, with known distances, are ideal targets to provide dynamical mass measurements to test the physics of evolutionary models at young ages and very low masses. We report for the first time the binarity of TWA22, possible new dynamical calibrator for evolutionary models at young ages. Based on an accurate trigonometric distance (17.53 +- 0.21 pc) determination, we infer a total dynamical mass of 220 +- 21 MJup for the system. From the resolved near-infrared integral-field spectroscopy, we find an effective temperature Teff=2900+200-200 K for TWA22 A and Teff=2900+200-100 K for TWA22 B and surface gravities between 4.0 and 5.5 dex. From our photometry and a M6 +- 1 spectral type for both components, we find luminosities of log(L/Lsun)=-2.11 +- 0.13 dex and log(L/Lsun)=-2.30 +- 0.16 dex for TWA22 A and B respectively. By comparing these parameters with evolutionary models, we question the age and the multiplicity of this system. We also discuss a possible underestimation of the mass predicted by evolutionary models for young stars close to the substellar boundary.