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Solar System Comets

Comets are frozen reservoirs of primitive solar dust grains and ices. Analysis (using thermal emission models and modern optical contants of a variety of amporphous and crystalline mineral species) of the composition and size distribution of cometary dust grains from optical/infrarared spectroscopy, imaging and polarimetry techniques expedites an appraisal of the physical characteristics of the solid materials that constituted the primitive solar nebula. The study of comets is an indirect probe of the origin of the constituents of the primitive solar system, their subsequent evolution into planetesimals, and their relationship to materials in other astrophysical environments.

This cometary research program utilizes both ground-based (e.g., the NASA IRTF, the Gemini Telescopes, the UM Mt. Lemmon Observatory, ESO VLT) and Spitzer Space Telescope infrared observations of the characteristics and temporal variations of the infrared spectral energy distributions (SEDs) that detail activity of comet nuclei and global dust properties, mid-infrared spectroscopy to ascertain dust mineralogy, and near-IR imaging polarimetry where the color and polarization maps of comet comae and tails are useful in understanding the physical properties of comet grains and comet nuclei. Some interesting highlights resulting from this program include the dsicovery of the 6 micron nu-2 water emission lines in comet C/2003 K4 (LINEAR), detection of "distributed" (i.e., "extended") CO+CO2 emission in the coma of comet 21/P Giacobini-Zinner, identification of crystalline silicates in 9P/Tempel excavated from sub-surface layers by the Deep Impact encounter, and studies of the rotational light curve 67P/Churyumov-Gerasimenko.

Classical Novae and CVs

Processes which contribute to the enrichment of the interstellar medium (ISM) metal abundance are of wide-ranging importance to such fields as galactic evolution, star formation, and the aggregation of planetary systems. Novae are important sources of highly processed material. Two decades of infrared observations of classical novae have established their importance as laboratories for the study of the production of astrophysical dust grains and as contributors to abundance anomalies that are known to characterize the ISM. The study of the abundances in novae ejecta also leads to an understanding of the evolution of and nucleosynthesis in white dwarf progenitor stars. The observed chemical abundances in the ejecta are end-products of the thermonuclear runaway reactions occurring on the surface of the white dwarf (WD) and dredge-up from the WD interior. They reflect the history of mass-transfer and accretion in the binary system, the WD interior chemical composition, and the mass of the nova progenitor.

The primary focus of our current novae research is directed toward assessing the chemical abundances, density, and mass of novae ejecta from coronal and forbidden emission line spectroscopy; determining the grain size distribution and mineral composition of novae dust; exploring differences in the temporal evolution of the broadband spectral energy distribution and light curves in carbon-nitrogen-oxygen (CNO) versus oxygen-neon-magnesium (ONeMg) novae; and conducting dynamical studies of novae ejecta. Data for this research program are collected from ground-based facilities and space mission such as NASA's Spitzer Telecescope, the Chandra X-ray Telescope, Swift, XMM-Netwon, and the Hubble Space Telescope. Through our extensive network of collaboration, world leading theorist model our observational data using state-of-the-art photoionization and dynamic modeling codes to help derive physical characteristics of these objects.

In the future, observations of novae in external galaxies in the local universe with future missions such, as SOFIA and the James Webb Space Telescope (6.5-m), will be important in establishing distance moduli, studies of chemical enrichment of the interstellar medium in other galaxies, and investigations of metallicity variations on stellar populations in galaxies.

Evolved Stellar Populations

Evolved stellar pops underconstruction.