Circumstellar discs around post-AGB binaries: a site for planet formation?

Most known planets find their origin in planet-forming discs around lower mass young stars. Planets are also detected around more exotic stars (e.g. massive stars) and around binary white dwarfs. The latter seems to point to the possible existence of second generation planet formation. One possibility for this second generation planet formation is given by a class of evolved stellar systems that show stable, dusty circumbinary discs, namely post-asymptotic giant branch (post-AGB) binary systems. These discs show remarkable similarities with planet-forming discs around young stars and enable us to study planet formation processes in a peculiar parameter space (short disc lifetimes, high stellar luminosity, different disc formation mechanisms). Using multi-wavelength infrared interferometric observations of such discs to spatially resolve the emission from the very inner regions, we gain insight into the physical condition in the disc inner regions. In this talk, I will present the results of our thorough observing campaign using all current VLTI instruments, PIONIER, GRAVITY, and MATISSE, to reveal the circumbinary disc around one such post-AGB binary system. I will show geometric and radiative transfer model results that reproduce the visibility data of all bands, providing strong implications on the disc structure and discuss the importance of such observing campaigns and the possible synergies with other facilities to constrain the structure and evolution of such discs