Finding new sub-stellar co-moving companion candidates - the case of CT Cha

TL;DR

This study identifies a faint, co-moving sub-stellar companion to the T Tauri star CT Cha using multi-epoch adaptive optics imaging, confirming its physical association and ruling out a background object.

Contribution

First detection of a co-moving sub-stellar companion around CT Cha using high-resolution imaging and proper motion analysis.

Findings

Faint companion at 2.67" separation (~440 AU) detected.

Companion shares proper motion with CT Cha, confirming physical association.

Background object hypothesis rejected with 4 sigma significance.

Abstract

We have searched for close and faint companions around T Tauri stars in the Chamaeleon star forming region. Two epochs of direct imaging data were taken with the VLT Adaptive Optics instrument NaCo in February 2006 and March 2007 in Ks band for the classical T Tauri star CT Cha together with a Hipparcos binary for astrometric calibration. Moreover a J band image was taken in March 2007 to get color information. We found CT Cha to have a very faint companion (Ks{0} = 14.6 mag) of ~ 2.67" separation corresponding to ~ 440 AU. We show that CT Cha A and the faint object form a common proper motion pair and that the companion is not a non-moving background object (with 4 sigma significance).