Title:Imaging Stars with CHARA-MIRC

Abstract:
Long baseline optical inerferometers now have the power to resolve objects as small as 0.5 
milliarcseconds in the near-IR, allowing us to study stars and their environment in unprecedented 
detail. We first present our study on rapid rotators. As a fundamental property of stars, rotation 
changes stars'' shape, surface brightness, luminosities, and Teffs, and also modifies the observed 
abundances of various elements.  Since most hot stars are rapid rotators, understanding the effects 
of rotation will shed light on critical areas of stellar evolution and basic astrophysics. Using 
CHARA-MIRC, we resolved the surface of Altair, resulting in the first image of a main sequence star 
other than the Sun. We also imaged and modeled Alp Oph and Alp Cep. Our results show that these 
stars are elongated and have bright poles and dark equators,  confirming the "gravity darkening" 
phenomenon. Our images show darker equators than that expected from the models, implying other 
mechanisms such as differential may exist in these stars. We also investigated the impact of rapid 
rotation to the status of these stars in the H-R diagram. In addition to rapid rotators, we will 
also present the first resolved images of the well-known interacting and eclipsing binary Beta 
Lyrae. Our results show that the mass donor is elongated due to Roche lobe overflowing. The disk 
surrounding the mass gainer is also elongated as expected and may be asymmetric. Our images and 
models also allowed us to obtain the full orbital parameters for Bet Lyrae for the first time ever.