Physics and Astronomy Calendar

Supernovae of type IIn possess spectral signatures that indicate an intense interaction between the supernova ejecta and surrounding dense circumstellar material 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. I will discuss ways in which polarized line profiles can be produced by the interaction between Type IIn supernovae and their circumstellar environments. I have constructed a Monte Carlo code that simulates the
transfer of the H alpha line through circumstellar shells with various geometrical configurations and optical characteristics. The superposition of broad and narrow line components produced in different regions of the circumstellar environment and modified by electron and resonance line scattering, hydrogen absorption, thermal emission, and geometrical and viewing angle effects gives rise to a variety of polarized line shapes in the model spectra. I compare these results with recent 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 intriguing objects.