Matteo Cantiello edited Abstract.tex  about 10 years ago

Commit id: 0c42893ae82fdeb8961883a61fad048a4fda11f5

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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.