Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): A
  close low mass companion to ET Cha
  To understand the formation of planetary systems, one needs to understand the
initial conditions of planet formation, i.e. the young gas-rich planet forming
disks. Spatially resolved high-contrast observations are of particular
interest, since substructures in disks, linked to planet formation, can be
detected and close companions or even planets in formation embedded in the disk
can be revealed. In this study we present the first result of the DESTINYS
survey (Disk Evolution Study Through Imaging of Nearby Young Stars). DESTINYS
is an ESO/SPHERE large program that aims at studying disk evolution in
scattered light, mainly focusing on a sample of low-mass stars (<1$M_\odot$) in
nearby (~200 pc) star-forming regions. In this particular study we present the
observations of the ET Cha (RECX 15) system, a nearby 'old' classical T Tauri
star (5-8 Myr, ~100 pc), which is still strongly accreting. We use SPHERE/IRDIS
in H-band polarimetric imaging mode to obtain high contrast images of the ET
Cha system to search for scattered light from the circumstellar disk as well as
thermal emission from close companions. We additionally employ VLT/NACO total
intensity archival data taken in 2003. We report here the discovery of a
low-mass (sub)stellar companion with SPHERE/IRDIS to ET Cha. We are estimating
the mass of this new companion based on photometry. Depending on the system age
it is a 5 Myr, 50 $M_{Jup}$ brown dwarf or an 8 Myr, 0.10 $M_\odot$ M-type
pre-main-sequence star. We explore possible orbital solutions and discuss the
recent dynamic history of the system. Independent of the precise companion mass
we find that the presence of the companion likely explains the small size of
the disk around ET Cha. The small separation of the binary pair indicates that
the disk around the primary component is likely clearing from the outside in,
explaining the high accretion rate of the system.
