A Novel Approach to Constrain Rotational Mixing & Convective-Core Overshoot in Stars Using the Initial-Final Mass Relation. (arXiv:1901.02904v1 [astro-ph.SR])

A Novel Approach to Constrain Rotational Mixing & Convective-Core Overshoot in Stars Using the Initial-Final Mass Relation. (arXiv:1901.02904v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Cummings_J/0/1/0/all/0/1">Jeffrey D. Cummings</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kalirai_J/0/1/0/all/0/1">Jason S. Kalirai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Choi_J/0/1/0/all/0/1">Jieun Choi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Georgy_C/0/1/0/all/0/1">Cyril Georgy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tremblay_P/0/1/0/all/0/1">Pier-Emmanuel Tremblay</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramirez_Ruiz_E/0/1/0/all/0/1">Enrico Ramirez-Ruiz</a>

The semi-empirical initial-final mass relation (IFMR) connects
spectroscopically analyzed white dwarfs in star clusters to the initial masses
of the stars that formed them. Most current stellar evolution models, however,
predict that stars will evolve to white dwarfs $sim$0.1 M$_odot$ less massive
than that found in the IFMR. We first look at how varying theoretical mass-loss
rates, third dredge-up efficiencies, and convective-core overshoot may help
explain the differences between models and observations. These parameters play
an important role at the lowest masses (M$_{rm initial}$ $<$ 3 M$_odot$). At higher masses, only convective-core overshoot meaningfully affects white dwarf mass, but alone it likely cannot explain the observed white dwarf masses nor why the IFMR scatter is larger than observational errors predict. These higher masses, however, are also where rotational mixing in main sequence stars begins to create more massive cores, and hence more massive white dwarfs. This rotational mixing also extends a star's lifetime, making faster rotating progenitors appear like less massive stars in their semi-empirical age analysis. Applying the observed range of young B-dwarf rotations to the MIST or SYCLIST rotational models demonstrates a marked improvement in reproducing both the observed IFMR data and its scatter. The incorporation of both rotation and efficient convective-core overshoot significantly improves the match with observations. This work shows that the IFMR provides a valuable observational constraint on how rotation and convective-core overshoot affect the core evolution of a star.

The semi-empirical initial-final mass relation (IFMR) connects
spectroscopically analyzed white dwarfs in star clusters to the initial masses
of the stars that formed them. Most current stellar evolution models, however,
predict that stars will evolve to white dwarfs $sim$0.1 M$_odot$ less massive
than that found in the IFMR. We first look at how varying theoretical mass-loss
rates, third dredge-up efficiencies, and convective-core overshoot may help
explain the differences between models and observations. These parameters play
an important role at the lowest masses (M$_{rm initial}$ $<$ 3 M$_odot$). At
higher masses, only convective-core overshoot meaningfully affects white dwarf
mass, but alone it likely cannot explain the observed white dwarf masses nor
why the IFMR scatter is larger than observational errors predict. These higher
masses, however, are also where rotational mixing in main sequence stars begins
to create more massive cores, and hence more massive white dwarfs. This
rotational mixing also extends a star’s lifetime, making faster rotating
progenitors appear like less massive stars in their semi-empirical age
analysis. Applying the observed range of young B-dwarf rotations to the MIST or
SYCLIST rotational models demonstrates a marked improvement in reproducing both
the observed IFMR data and its scatter. The incorporation of both rotation and
efficient convective-core overshoot significantly improves the match with
observations. This work shows that the IFMR provides a valuable observational
constraint on how rotation and convective-core overshoot affect the core
evolution of a star.

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