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Evolution of stars just below the critical mass for iron core formation

Published online by Cambridge University Press:  05 September 2012

Koh Takahashi
Affiliation:
Department of Astronomy, Graduate school of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan email: ktakahashi@astron.s.u-tokyo.ac.jp
Hideyuki Umeda
Affiliation:
Department of Astronomy, Graduate school of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan email: ktakahashi@astron.s.u-tokyo.ac.jp
Takashi Yoshida
Affiliation:
Department of Astronomy, Graduate school of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan email: ktakahashi@astron.s.u-tokyo.ac.jp
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Abstract

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We calculate the evolution of stars with their initial mass of 9-11M under very fine initial mass grid of 0.01M. We determine the lower critical mass for Ne ignition in an ONe core that has not undergone the thermal pulse episode. The values are 9.83M for the initial mass and 1.365M for the CO core mass. A star with an initial mass slightly larger than the critical, undergoes an off-center Ne+O ignition. Since the energy production rate of Ne+O burning and lasting electron capture reactions is sufficiently large to ignite Si, an Fe core forms as a result of shell Si burning. For a star just below the critical mass, an ONe core continues to contract. In such a high density core, electron capture by nuclei produced through C burning affects the core evolution. After 20Ne starts to capture electrons, the core may ignite O and undergo O detonation. The fate may be an Electron Capture Supernova.

Type
Poster Papers
Copyright
Copyright © International Astronomical Union 2012

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