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Meredith L. Rawls edited subsection_Stellar_evolution_and_tidal__.tex
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\begin{itemize}
\item Mass loss: Adding a prescription for moderate red-giant-branch mass loss ($\eta = 0.4$, see \citealt{mig12}) to the MESA model does not appreciably change stellar radius as a function of evolutionary stage. Even a more extreme mass-loss rate ($\eta = 0.7$) does not significantly affect the radii, essentially because the star is too low-mass to lose much mass.
\item He abundance: Increasing the initial He fraction in the MESA model does not allow for smaller stars in the red clump phase, because shell-H burning is very efficient with additional He present. As a result, the star maintains a high luminosity and therefore a larger radius as it evolves from the tip of the red giant branch to the red clump.
\item Convective overshoot: The MESA models in this work assume a reasonable overshoot efficiency as described above ($f = 0.016$). We tried varying this from 0--0.03, and can barely make a red clump star as small as $R_2 \simeq 8.3 \ R_\odot$ when $f = 0.01$. With less overshoot, the RGB phase as shown in Figure \ref{fig:mesa} increases in duration,
more readily allowing which allows a higher probability for stars
with of $M_1 = 2.16 \ M_\odot$ and $M_2 = 2.14 \ M_\odot$ to
both be
coeval. on the RGB.
\item Mixing length: Increasing the mixing-length parameter $\alpha$ from the standard solar value of 2 to 3 in the MESA model, which effectively increases the efficiency of convection, does produce a red clump star small enough to agree with both measured radii. This is because it reduces the temperature gradient in the near-surface layers, increasing the effective temperature while reducing the radius at constant luminosity.
\item Period spacing: The noisy period spacing estimate ($\Delta \Pi \simeq 150 \ \rm{sec}$) may not be measuring what we expect due to possible rotational splitting of mixed oscillation modes. If the true period spacing is closer to $\Delta \Pi \simeq 80 \ \rm{sec}$, this would explain the disagreement. A detailed discussion of rotational splitting behavior in slowly rotating red giants is explored in \citet{gou13}.
\end{itemize}