AAS 207th Meeting, 8-12 January 2006
Session 171 Supernovae
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[171.15] Polarized Line Profiles as Diagnostics of Circumstellar Geometry in Type IIn Supernovae

J.L. Hoffman (UC Berkeley), P. Nugent (LBL), D.C. Leonard (Caltech), A.V. Filippenko (UC Berkeley)

Supernovae of type IIn possess spectral signatures that indicate an intense interaction between the supernova ejecta and surrounding dense circumstellar material, presumably cast off by the star in pre-explosion mass-loss episodes. Studying this interaction can yield clues to the nature of Type IIn progenitors and their mass loss history. In particular, polarization spectra of Type IIn's show complex line polarization and position angle features that arise from a combination of geometrical and optical effects. We investigate ways in which polarized H alpha line profiles can be produced at early times in the evolution of a Type IIn supernova by modeling the transfer of the photospheric H alpha line through circumstellar shells with various geometrical configurations and optical characteristics. Electron scattering combined with hydrogen absorption, thermal emission, and resonance line effects produces a variety of polarized line shapes. We compare our results with high-quality spectropolarimetric observations of Type IIn supernovae, and show how they can be used to constrain the characteristics of the circumstellar material in these objects.

J.L. Hoffman is supported by an NSF Astronomy & Astrophysics Postdoctoral Fellowship under award AST-0302123. This research uses the resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

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