Probing Supernova Asymmetry With Spectropolarimetric Modeling of Clumpy Ejecta

Type Conference Paper
Names K. Tabetha Hole, D. Kasen, K. H. Nordsieck, J. S. Gallagher
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #211, #105.15
Volume 39
Pages 931
Date December 1, 2007
Library Catalog NASA ADS
Abstract Polarization has been detected at early times for all types of supernova, indicating that all such systems result from or quickly develop some form of asymmetry. In addition, the detection of strong line polarization in supernovae is suggestive of chemical inhomogeneities ("clumps") in the layers above the photosphere, which may reflect hydrodynamical instabilities during the explosion. We have developed a fast, flexible, approximate semi-analytic code for modeling polarized line radiative transfer within 3-D inhomogeneous rapidly-expanding atmospheres. Given a range of model parameters, the code randomly generates sets of clumps in the expanding ejecta and calculates the emergent line profile and Stokes parameters for each configuration. The ensemble of these configurations represents both the effects of various host geometries and of different viewing angles. We present results for the first part of our survey of model geometries, specifically the effects of the number of clumps, size and distance from the photosphere (and the related effect of filling factor) on the emergent spectrum and Stokes parameters. We have also developed a method to connect the results of our simulations to robust observational parameters such as maximum degree of polarization and polarized flux throughout the line. Our models, in connection with spectropolarimetric observations, will be useful in constraining the 3-D structure of supernova ejecta, which may offer important insight into the supernova explosion physics or the nature of the progenitor system.
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