Recently I have been investigating the radiative transfer processes occurring in circumstellar disks surrounding hot stars. These disks occur most frequently around B-type, main sequence, stars and such systems are called "Be stars". Here the "e" stands for emission, and this designation is used because these systems exhibit emission lines of hydrogen in their spectrum arising from the circumstellar material. The circumstellar material surrounding Be stars is thought to be ejected from the central star, but how such disks form and evolve remain open questions. Be stars are known to be the most rapidly rotating of main sequence stars, but the connection between rotation and formation of the disk remains elusive. The study of Be stars couples the themes of stellar rotation and angular momentum, stellar mass loss, stellar pulsation, and stellar evolution. Because Be star systems are often bright, they can be subject to strong observational constraints (such as direct interferometric imaging) and hence can provide ideal "test-beds" for the physics of disks.
I am particularly interested in modeling the thermal structure of these disks using the techniques of non-LTE radiative transfer. I have developed a suite of programs (bedisk/beray) that can determine the temperature distribution in such disks (see animation to the right) and can predict the emission line spectrum, the spectral energy distribution of the disk+star, and interferometric visibilities.
Current student projects
Ahmed Ahmed (PhD): The Nitrogen Abundance of Be stars: Evidence for Rotational Mixing?
Parshati Patel (PhD): The Inner Gaseous Disks of Herbig Ae/Be Stars
Ethan Rowe (PhD): Diagnostics of Turbulence in Be Star Disks