Thursday

The evolution of massive stars is governed by mass-transfer processes, including mass accretion during the early stages and extreme mass ejections during the late stages of stellar evolution. Infrared interferometers, such as the VLT Interferometer (VLTI), allow us now to constrain the distribution and kinematics of the circumstellar matter at these evolutionary phases with unprecedented, milliarcsecond angular resolution. This enables studies on outflow-launching during the protostellar phase, on stellar winds and stellar surface structures during the main-sequence and supergiant phase, and on the geometry of the mass-loss processes during the Wolf-Rayet or Luminous Blue Variable phase. In this talk, we outline the unique observational capabilities of the VLTI array and show examples on how these capabilities can be applied for studying massive stars. This is timely, as the VLTI is currently undergoing a transformation with the arrival of the second-generation instruments GRAVITY and MATISSE, offering significantly-enhanced sensitivity, wavelength coverage, and imaging capabilities. We also give an overview about the newly-established, OPTICON-funded network of VLTI Expertise Centres, where a UK branch is being established at the University of Exeter. These centres provide a contact point for first-time VLTI users and can provide assistance from the proposal preparation to the data reduction stage.