New textsl{s}-process Site in Rapidly-Rotating Massive Pop II Stars. (arXiv:1906.07335v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Banerjee_P/0/1/0/all/0/1">Projjwal Banerjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heger_A/0/1/0/all/0/1">Alexander Heger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qian_Y/0/1/0/all/0/1">Yong-Zhong Qian</a>

We report a new site for the textsl{s}-process in rotating massive
metal-poor stars. Above a critical rotation speed, such stars evolve in a
quasi-chemically-homogeneous fashion, which gives rise to a prolific
textsl{s}-process. Rotation-induced mixing results in primary production of
$^{13}$C, which subsequently makes neutrons via
$^{13}mathrm{C}(alpha,mathrm{n})^{16}mathrm{O}$ during core He burning.
Neutron capture can last up to $sim 10^{13},mathrm{s}$ with the peak central
neutron density ranging from $sim10^7$ to $10^{8},mathrm{cm}^{-3}$.
Depending on the rotation speed and the mass loss rate, a strong
textsl{s}-process can occur with production of elements up to Bi for
progenitors with initial metallicities of $[Z]lesssim -1.5$. This result
suggests that rapidly-rotating massive metal-poor stars are likely the first
site for the main textsl{s}-process. We find that these stars can potentially
explain the early onset of the textsl{s}-process and some of the
carbon-enhanced metal-poor (CEMP-textsl{s} and CEMP-textsl{r/s}) stars with
strong enrichment attributed to the textsl{s}-process or a mixture of the
textsl{r}-process and the textsl{s}-process.

We report a new site for the textsl{s}-process in rotating massive
metal-poor stars. Above a critical rotation speed, such stars evolve in a
quasi-chemically-homogeneous fashion, which gives rise to a prolific
textsl{s}-process. Rotation-induced mixing results in primary production of
$^{13}$C, which subsequently makes neutrons via
$^{13}mathrm{C}(alpha,mathrm{n})^{16}mathrm{O}$ during core He burning.
Neutron capture can last up to $sim 10^{13},mathrm{s}$ with the peak central
neutron density ranging from $sim10^7$ to $10^{8},mathrm{cm}^{-3}$.
Depending on the rotation speed and the mass loss rate, a strong
textsl{s}-process can occur with production of elements up to Bi for
progenitors with initial metallicities of $[Z]lesssim -1.5$. This result
suggests that rapidly-rotating massive metal-poor stars are likely the first
site for the main textsl{s}-process. We find that these stars can potentially
explain the early onset of the textsl{s}-process and some of the
carbon-enhanced metal-poor (CEMP-textsl{s} and CEMP-textsl{r/s}) stars with
strong enrichment attributed to the textsl{s}-process or a mixture of the
textsl{r}-process and the textsl{s}-process.

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