Studying the Inner Regions of Young Binary Systems using Near-Infrared Interferometry

Planets form in the gas+dust discs around young stars. Once the planets have gained sufficient mass they open gaps in the disc surface structure, as might be observed in systems such as HL Tau. Various searches have been conducted in order to detect the gap-opening planets themselves, but with limited success. Therefore, the properties of the putative gap-opening bodies need to be inferred indirectly from the observed gap geometry. The essential next step is to study tidal interactions in cases where the properties of the interacting bodies, in particular their mass and orbit, are well-known. Such cases can be found in young close binary systems, where a low-mass stellar companion orbits a more massive central star on timescales of a few hundred days to a few years. These companions can either truncate the disc or open gaps, probing similar dynamical processes as in planet formation. The 3-D orbits and masses of the companions can be measured using radial velocity measurements and infrared interferometric observations. At the same time, the geometry of the tidally-opened gap can now be measured at longer wavelengths, for instance with VLTI mid-infrared interferometry and ALMA sub-millimetre interferometry.
The aim of this PhD project is to study a sample of young binary systems with infrared/sub-millimeter interferometry, to derive 3-D orbits, and to measure the tidal influence that the companions exerts on the disc structure. We will constrain fundamental stellar & disc parameters and derive the accretion rate onto the companion star, providing an important benchmark for modelling disc clearing and accretion processes in planet-forming discs.