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Matteo Cantiello edited Abstract.tex
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Stars Asteroseismology of $1.0-2.0M_\odot$ red giants by the \emph{Kepler}
satellite has enabled the first definitive measurements of interior
rotation in both first ascent red giant branch (RGB) stars and those
on the Helium burning clump. The inferred rotation rates are 10-30
days for the $\approx 0.2M_\odot$ He degenerate cores on the RGB and
30-100 days for the He burning core in a clump star. Using the MESA
code we calculate state-of-the-art stellar evolution models of low
mass rotating stars from the zero-age main sequence
to the cooling white dwarf (WD) stage. We include transport of angular
momentum due to rotational mixing and magnetic fields in radiative
zones (generated by the Tayler-Spruit dynamo). We find that all models
fail to predict core rotation as slow as observed on the RGB and
during core He burning, implying that an unmodeled angular momentum
transport process must be operating on the early RGB of low mass
stars. Later evolution of the star from the He burning clump to the
cooling WD phase appears to be at nearly constant core angular
momentum. We also incorporate the adiabatic pulsation code, ADIPLS, to
explicitly highlight this shortfall when applied to a specific
\emph{Kepler} asteroseismic target, KIC8366239.
%Stars are born rotating. Observations during the main sequence reveal that the majority of objects with mass above
$\approx %$\approx 1.5\mso$ are spinning fairly rapidly. From the zero-age main sequence to the final compact remnant angular
momentum %momentum is transported through the star. Theoretical calculations can make predictions about the evolution of the
internal %internal angular momentum distribution. Thanks to asteroseismology and in particular to the \textit{Kepler} satellite
it %it is now possible to test these predictions. The observed mixed modes now yield measurements of the core rotation in
red %red giants and clump stars. Here we calculate state-of-the-art stellar evolution models of rotating low-mass stars in
the %the mass range $1.5-3.0 \mso$ from their zero-age main sequence to the cooling white dwarf stage. These models include
transport %transport of angular momentum due to rotational mixing and magnetic fields in radiative zones (generated by the
Tayler-Spruit %Tayler-Spruit dynamo). All models fail to predict core rotation as slow as observed on the RGB and during core He
burning, %burning, implying that an unmodeled angular momentum transport process must be operating on the early RGB of low mass
stars. %stars.
%To test such predictions, rotational periods can be observed, providing a direct constraint of the surface rotation rate. %Moreover the efficiency of internal transport mechanisms can sometimes be inferred by using indirect proxies, for example %the change in the surface abundances of certain isotopes. This is because the same instabilities and/or circulations %believed to be responsible for the angular momentum transport can also displace chemicals in the radial direction. %Recently it has also become possible to directly probe the rotation profile of stars other than the Sun. This is thanks %to asteroseismology: using the splitting of mixed modes it is possible to measure the degree of differential rotation %between core and envelope. Here we calculate state-of-the-art stellar evolution models of rotating low-mass stars in the %mass range $1.5-3.0 \mso$ from their zero age main sequence to the cooling white dwarf stage. These models include %transport of angular momentum due to rotational mixing and magnetic fields in radiative zones (generated by the Spruit-%Tayler dynamo). We show how the predictions of these calculations compare to the available observational constraints, %with a particular emphasis on the asteroseismic information coming from KEPLER observations of red giant stars.