Confirmation of CT Cha b

New astrometry and photometry for the companion candidates of CT Cha
http://arxiv.org/abs/0905.1936

Abstract wrote:

In our ongoing search for close and faint companions around T Tauri stars in the Chamaeleon star-forming region, we recently (Schmidt et al 2008b) presented direct observations and integral field spectroscopy of a new common proper motion companion to the young T-Tauri star and Chamaeleon member CT Cha and discussed its properties in comparison to other young, low-mass objects and to synthetic model spectra from different origins. We now obtained for the first time direct H-Band observations of the companion CT Cha b and of another faint companion candidate (cc2) approximately 1.9 arcsec northeast of CT Cha using the Adaptive Optics (AO) instrument Naos-Conica (NACO) at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in February 2008.
From these data we can now exclude by 4.4 & 4.8 sigma that CT Cha b is a non-moving background object and find cc2 to be most likely a background star of spectral type <= K4 with a proper motion of mu{alpha} cos{delta} = -8.5 +/- 5.7 mas/yr and mu{delta} = 12.0 +/- 5.6 mas/yr, not consistent with being a member of the Cha I star-forming region.

Finding new sub-stellar co-moving companion candidates - the case of CT Cha
http://arxiv.org/abs/0905.1921

Abstract wrote:

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).