Studying the Environment of Symbiotic Stars with Spitzer IRS Spectroscopy

We present high resolution (R 600) spectra of five symbiotic stars obtained with the Spitzer Space Telescope IRS instrument (9.9-37.2 microns). Of these stars, three (BI Cru, Hen2-104, and V1016 Cyg) are D-type, two (AS201 and V417 Cen) are D'-type, and one (AG Peg) is a S-type. The spectrum of AG Peg contains strong hydrogen recombination and emission lines, including lines of [Ne V] at 14.32 microns and 24.32 microns along with [O IV] 25.89 micron emission. All of the D-type stars contain silicate features and strong lines of ions of sulfur and neon. The spectra of the D'-type stars contain few strong emission lines, though the spectrum of AS201 does contain the [Ne II] 15.56 micron line. As part of a program to study the evolution and environments of symbiotic stars using Spitzer MIPS and IRS observations, we use line ratios and analysis of the silicates in the spectra to report environmental conditions in these systems.