Identification of the TW Hya Association member 2M1235$-$39: a tertiary component of the HR 4796 system

TL;DR

This study confirms that 2M1235-39 is a member of the TW Hya Association and likely a wide, low-mass tertiary component of the HR 4796 system, based on spectroscopic and proper motion data.

Contribution

It provides the first spectroscopic and proper motion evidence linking 2M1235-39 to the TW Hya Association and identifies it as a tertiary component of HR 4796.

Findings

2M1235-39 is a TWA member based on spectral lines and proper motion.

It is a low-mass (M4.5) star with a wide separation from HR 4796.

Likely a tertiary component at 13,500 AU separation.

Abstract

The association of the late-type star 2MASS J12354893-3950245 (2M1235-39) with a bright X-ray source detected serendipitously by ROSAT and XMM-Newton, combined with its proximity to the well-studied (A+M binary) system HR 4796, suggests this star is a member of the TW Hya Association (TWA). To test this hypothesis, we used optical spectroscopy to establish the Li and H-alpha line strengths and spectral type of 2M1235-39, and determined its proper motion via optical imaging. The Li absorption and H-alpha emission line strengths of 2M1235-39, its near-IR and X-ray fluxes, and its proper motion all indicate that 2M1235-39 is a TWA member. Most likely this star is a wide (13,500 AU) separation, low-mass (M4.5), tertiary component of the HR 4796 system.