CfA Colloquium Schedule Fall 2007
 29 November 2007

29 November 2007

Speaker: Julia Lee (Harvard University)

Title: The dirt on dust composition: an X-ray perspective

Abstract: There is a multi-wavelength (radio-IR) industry focused on the problem of astrophysical dust. Yet, despite extensive studies, and good progress, there remains much to understand of dust properties (size, composition, and distribution) in astrophysical environments, from the colder ISM environs to the hotter environments near the disks and envelopes of young stars and compact sources. If nothing else, dust is everywhere, and for many astrophysical topics, its presence hinders our studies in some way, be it to extinguish a UV part of a spectrum, or possibly affect Cosmology results. In the course of trying to study the plasma conditions in BH systems (Chandra studies of warm absorbers), we discovered interesting line and edge structure which pointed to direct X-ray detections of dust. I will discuss the program we have since developed to determine grain composition using combined X-ray laboratory+space efforts. Specifically, I will discuss how we can apply experimental solid state physics techniques to the study of astrophysical dust (as facilitated by Chandra HETGS pointings towards luminous accretion systems in Galactic X-ray binaries and supermassive black holes in extragalactic AGN) to possibly probe grain/molecule types missed by non-X-ray efforts. I will also show our initial results which hint at different dust composition along different lines-of-sight, and in different environments ranging from X-ray binaries (e.g. GRS 1915+105, Cygnus X-1) to dusty AGN (e.g. MCG -6-30-15, IRAS 13349+2438), and how this is all tied into "warm absorber" modeling efforts. Together, with Spitzer, we anticipate a unique probe of dust location and properties.

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