Unraveling the Dusty Environment around Evolved Star RT-Vir with Radiative Transfer Modeling

From stellar evolution to planet and star formation, cosmic dust plays a role in many important astronomical processes. It follows then, that a thorough understanding of dust in these environments will improve our understanding of the processes in which it plays a part. To this end, we have been studying the dusty environment around the asymptotic giant branch (AGB) star RT Virginis. AGB stars are responsible for producing a significant portion of the dust in our galaxy, and RT Vir is a useful example to study as a dust-producing star with low optical depth and especially broad spectral features.

The dust around RT Vir has been observed by several infrared (IR) observatories. We use published IR spectra from the IR Space Observatory (ISO). To analyze this spectrum, we use the one-dimensional radiative transfer modeling code DUSTY. DUSTY allows us to simulate the spectral energy distribution of dust measured by observatories like ISO. By fitting DUSTY models to RT Vir dust spectra, we can determine the density of the dust shells, their density distribution, relative abundances of different compositions of dust grains, as well as their temperature throughout the dust shell. Preliminary modeling suggests that the dust shell is composed primarily of silicates ~25%, iron ~8%, iron and aluminum oxides ~33% in a geometrically thin shell.

This project provides the proof-of-concept for the remainder of a PhD-program which will expand the study to a larger sample of nearby AGB stars in the interest of determining what dust formation mechanisms may be more likely around certain dust-forming AGB stars.