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J. W. Murphy, A. Burrows (Steward Observatory, The University of Arizona), A. Heger (Los Alamos National Laboratory, T-6 Division)
An outstanding question surrounding the formation and evolution of neutron stars is the mechanism for natal kicks. While a significant fraction of pulsars shows evidence for a relatively large impulse at birth, a large number experience more modest kicks. It is, therefore, likely that more than one mechanism is responsible for the comprehensive distribution of pulsar speeds. Of the many mechanisms suggested for the largest kicks, recoils during stellar collapse and explosion, a possible consequence of large initial asymmetries in the cores of progenitor massive stars, are strong candidates. However, the success of this mechanism depends upon the existence of significant core asymmetries. Overstable g-modes trapped in the Fe core by the Si and O convective burning layers may provide the requisite asymmetries (Goldreich, Lai, and Sahrling 1997). We have performed a modal analysis of published core structures and derived eigenfrequencies and eigenfunctions, including the nonadiabatic effects of growth by nuclear burning and decay by both neutrino losses and acoustic losses to the outer envelope. We discuss the stability or instability of these modes as a function of progenitor mass and how our results bear on the issue of pulsar and neutron star natal kicks.
The author(s) of this abstract have provided an email address for comments about the abstract: jmurphy@as.arizona.edu
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Bulletin of the American Astronomical Society, 36 #2
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