A systematic survey of grain growth in discs around post-AGB binaries with PACS and SPIRE photometry

Post-AGB stars are the final stage of evolution of low-intermediate mass stars (M<8 Solar Masses). Those in binary systems have stable circumbinary discs. Using data from Herschel (PACS/SPIRE), we extend the SEDs of 50 galactic post-AGB binary systems to sub-millimetre wavelengths and use the slope of the SED as a diagnostic tool to probe the presence of large grains. Using a Monte Carlo radiative transfer code (MCMax), we create a large grid of models to quantify the observed spectral indices and use the presence of large grains in the disc as a proxy for evolution.