Collaborative Research: Dust formation around carbon stars: astromineralogy and the condensation sequence

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This research is motivated by the need to better understand the role of dust inastrophysical environments. Dust is a vital ingredient in the star formation process aswell as in planet forming disks. It is a source of mass loss from evolved stars (throughradiation pressure on dust grains) and intimately links the radiation field to thecircumstellar material. Dust also contributes to several aspects of interstellar processessuch as gas heating and the formation of molecules. The work to be undertaken here is specifically centered on characterizing the precise nature of dust grains around cool carbon stars as these are the source of the bulk of the Galaxy's carbon-rich dust. Byknowing the initial state of the dust from such stars, the effects of the dust in theinterstellar medium can be more accurately quantified. Moreover, the relatively benignenvironment surrounding such stars simplifies the chemistry, which in turn facilitates theunderstanding of the various processes in operation. The properties of the grains are alsotied to the evolution of the star itself, thus the precise nature of the dust must be assessedin order to understand this evolution. Finally, recent Spitzer Space Telescopeobservations of carbon stars in the Magellanic Clouds suggest a different dustcondensation sequence compared to Galactic carbon stars which may well permit theeffects of metallicity on dust formation to be investigated.The tools to be applied here include infrared spectroscopy and imaging, radiative transfermodeling, laboratory spectroscopy, and archival data mining. They will be used to testcurrent theories of dust formation in carbon star environments and how thesecondensation sequences are effected by the initial mass and metallicity of the parent stars.Furthermore, the imaging and radiative transfer studies should provide insight into thecauses of axisymmetric structures seen in planetary and protoplanetary nebulae.This project includes the participation and training of a doctoral student who will be anintegral part of the research program. The student will be expected to present results atboth conferences and public talks thereby combining training with public outreach.