Amy Steele, University of Maryland

There is evidence of circumstellar (CS) material around main sequence (MS), giant, and white dwarf (WD) stars that originates from the small-body population of planetary systems. How (if at all) are the planetesimals around MS and WD stars related? One way to address this question is to begin at the end, with the 30% of WDs that have unexpected heavy elements in their photospheres. This “pollution” likely arises from the accretion of planetesimals that were perturbed by outer planet(s) into the WD’s tidal radius. These planetesimals sublimate, turning into circumstellar (CS) gas, and then accrete onto the WD surface. In this talk, I describe a method for determining the abundances of elements in CS gas producing absorption features in the spectra of polluted WDs. This method will provide a key to understanding the instantaneous composition of the material flowing from the planetesimals, will guide modeling of the transits and of the dust in these polluted systems, and will help constrain the radial locations of different gas components.