New astrometry and photometry for the companion candidates of CT Cha

Abstract

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.

4 pages, 2 figures, Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun, St Andrews - Scotland, July 21-25 2008