AAS Meeting #193 - Austin, Texas, January 1999
Session 47. Supernovae
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[47.15] Asymmetrie in Core Collapse Supernovae

L. Wang, J.C. Wheeler, P. Hoeflich, A. Howell (University of Texas)

A direct way to study the geometry of supernova ejecta is to observe them in polarized light. Our program of supernova polarimetry aims at getting spectropolarimetric data of any supernova brighter than 14th magnitude that are accessible to the polarimeter mounted at the telescopes at the McDonald Observatory. The goal is to build up a sample of supernovae with polarimetric data. Our existing data show that all of the core-callapse (Type II, Ib/c) supernovae in our sample show measurable polarizations up to 1 supernova displays polarization larger than 0.2 maximum light. There is one Type Ia supernova (SN 1997bp) that is polarized at 1 optical maximum. A recent example among our data set is the Type IIn supernova 1998S which is polarized by more than 1.5 existence of a highly aspherical shell which is optically thick to electron scattering. The fact that core-collapse supernovae are systematically polarized was unexpected, but is not at all surprising considering other facts such as pular kick velocity, apshericities of young supernova remnants, the possible binary nature of the supernova progenitors, and the apparent aspherical appearance of mass loss from some well-observed red supergaints. There is, in fact, no evidence for spherical ejecta at all. The observe degree of polarization indicates that the ejecta of core-collapse supernovae must have axial ratios around or above 2:1 if modeled in terms of prolate or oblate spheroids. We conclude from our observations that core-collapse events must be intrinsically aspherical, whereas Type Ia supernova are much less aspherical.

The author(s) of this abstract have provided an email address for comments about the abstract: lifan@tao.as.utexas.edu

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