This project is motivated by recent results from interferometric optical and infrared telescopes that have begun to resolve the surfaces of rapidly rotating stars. Recent stellar models have demonstrated that the effects of rotation are far from negligible and can influence the lifetimes, surface brightnesses, surface abundances, and evolutionary tracks of rapidly rotating stars. Here, the investigators will take advantage of a new instrument, the Michigan Infrared Combiner (MIRC), which was commissioned last year at the Georgia State University Center for High Angular Resolution Astronomy's 6-telescope optical interferometer. With it, they will survey the surfaces of fast rotating stars, directly mapping the latitude-dependence of gravity darkening and testing the von Zeipel-Roche model for such stars. Through detailed modeling of the line profiles, spectral energy distributions, and interferometry visibilities/closure phases, quantitative models of the stellar photospheres' oblateness and gravity darkening laws will be developed. This work will be compared to the recent models to constrain the internal structure and nature of differential rotation in hot stars for the first time. Finally, the continuum emission of Be star disks will also be imaged, which when combined with emission line measurements and the spectral energy distribution, will allow the construction of the most accurate disk models to date. The goal is to determine the temperature structure and density of the disks and to link these properties back to the formation mechanism.
The work here will form the Ph.D. thesis of a graduate student who will be trained in the use of forefront astronomical instrumentation. The general purpose analysis tools and imaging algorithms will be made publicly available for use by other researchers. An education and public outreach program will also be undertaken which will center around infrared imaging technology, including a series of traveling exhibits organized through the Ann Arbor Hands-on Museum.
