The Circumstellar Structure and Massive Progenitors
Jennifer
L. Hoffman |
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In the past few years, more and more supernovae have been discovered
whose spectra show signatures of interaction with circumstellar material ejected
by their evolved progenitor stars. Studying the environments of these "interacting
supernovae", which include members of the Type IIn subclass, can yield important
information about core-collapse progenitors and the role of mass loss in the end
stages of massive stellar evolution. One obstacle to understanding these supernovae
has been their heterogeneity as a group; the IIn supernovae alone span a broad range
of spectral characteristics, light-curve morphologies, intrinsic brightnesses, and
many other properties. Spectropolarimetric observations provide a way to break the
degeneracies often inherent in supernova spectra; analysis of polarized spectra may
thus hold the key to subdividing the category of interacting supernovae and thereby
constraining the properties of their progenitors. One common signature of interacting supernovae is the presence of a strong narrow Hα line, often consisting of several superposed components and often intrinsically polarized by scattering in the circumstellar envelope. I will present results from numerical modeling of Hα line profiles in direct and scattered light that provide clues to the geometrical structure of the circumstellar material around interacting supernovae. I will also review the observed line profile behavior of Type IIn supernovae and its correlations with other supernova characteristics. Finally, I will discuss what these results can tell us about the massive stellar progenitors of interacting supernovae. |
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For more information, please send email to Jennifer. June 1, 2007 |