Near Infrared View of Stellar Surfaces and Circumstellar Disks with an Upgraded Optical Interferometer.

Abstract

Modern long-baseline optical interferometers can reach sub-milliarcsecond angular resolutions, allowing us to resolve the detailed structures over stellar surfaces as well as circumstellar disks. Through modeling and imaging two rapidly rotating stars observed in H band by the interferometer CHARA/MIRC, I will show how the rotation affects the stellar geometries, surface temperature distributions and evolutions. A high-eccentricity Be binary system was observed right after its periastron by the same interferometer, providing an opportunity to study whether the gravitational interference from the secondary would trig the gaseous disk formation around the primary. I have also worked on three instrumental projects to improve the scientific results from the interferometer. In order to reduce the uncertainty of visibility measurements from MIRC, I have developed Photometric Channels to directly measure the fluxes of individual beams in the real time. MIRC has further been expanded from a 4-beam combiner to a 6-beam combiner to improve the (u,v) coverage to image more complicated systems. Lastly we have been developing Wavefront Sensors of the Adaptive Optics systems on the CHARA telescopes to improve the sensitivity to study fainter objects such as the innermost edges of YSO disks.