High Angular Resolution Observations of High Mass Loss Red Supergiants

High mass loss occurs from the extended atmospheres of red supergiants (RSGs). RSGs are an important contributor to the chemical enrichment of the Universe. Current models of the extended atmospheres of RSGs do not agree with observations. Previous studies concluded that pulsation and convection processes alone cannot explain the mass loss behavior. Additionally, fits of effective temperatures in optical TiO bands result in poor fits in the near-infrared continuum bands, which can lead to incorrect spectral typing. Thus new semi-empirical models are necessary. We present initial optical and near-infrared interferometric observations obtained with the Center for High Resolution Angular Astronomy (CHARA) Array of the RSGs SW Cep and PZ Cas. High angular resolution interferometric observations allow us to probe the extended atmospheres and obtain precise diameters. We derive the fundamental parameters of these stars and compare their diameters at different wavelengths to test semi-empirical models of extended atmospheres. In future work we plan to extend this work to a larger sample of stars and identify molecular lines in the extended atmospheres to improve our understanding of mass loss mechanisms.