The Evolution of Massive Helium Stars Including Mass Loss. (arXiv:1901.00215v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Woosley_S/0/1/0/all/0/1">S. E. Woosley</a>
The evolution of helium stars with initial masses in the range 1.6 to 120
Msun is studied, including the effects of mass loss by winds. It is assumed
that these stars are formed in binary systems when their expanding hydrogenic
envelopes are promptly lost at helium ignition. Significant differences are
found with single star evolution, chiefly because the helium core loses mass
during helium burning rather than gaining it from hydrogen shell burning.
Consequently presupernova stars for a given initial mass function have
considerably smaller mass when they die and will be easier to explode. Even
accounting for this difference, the helium stars with mass loss develop more
centrally condensed cores with compactness that is less variable than their
single-star counterparts. The production of low mass black holes may be
diminished. Helium stars with initial masses below 3.2 Msun experience
significant radius expansion after helium depletion, reaching blue supergiant
proportions. This could trigger additional mass exchange or affect the light
curve of the supernova. The most common black hole masses produced in binaries
is estimated to be about 7 to 9 Msun. A new maximum mass for black holes
derived from pulsational pair-instability supernovae is derived – 46 Msun, and
a new potential gap at 10 – 12 Msun is noted. Models pertinent to SN 2014ft are
presented and a library of presupernova models is generated.
The evolution of helium stars with initial masses in the range 1.6 to 120
Msun is studied, including the effects of mass loss by winds. It is assumed
that these stars are formed in binary systems when their expanding hydrogenic
envelopes are promptly lost at helium ignition. Significant differences are
found with single star evolution, chiefly because the helium core loses mass
during helium burning rather than gaining it from hydrogen shell burning.
Consequently presupernova stars for a given initial mass function have
considerably smaller mass when they die and will be easier to explode. Even
accounting for this difference, the helium stars with mass loss develop more
centrally condensed cores with compactness that is less variable than their
single-star counterparts. The production of low mass black holes may be
diminished. Helium stars with initial masses below 3.2 Msun experience
significant radius expansion after helium depletion, reaching blue supergiant
proportions. This could trigger additional mass exchange or affect the light
curve of the supernova. The most common black hole masses produced in binaries
is estimated to be about 7 to 9 Msun. A new maximum mass for black holes
derived from pulsational pair-instability supernovae is derived – 46 Msun, and
a new potential gap at 10 – 12 Msun is noted. Models pertinent to SN 2014ft are
presented and a library of presupernova models is generated.
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