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Stellar Modeling of Oscillation Frequencies in a Sample of Red Giants
Jean McKeever (New Mexico State University), Jason Jackiewicz (New Mexico State University), Patrick Gaulme (New Mexico State University)
The study of red giants in eclipsing binaries has allowed for the best in-depth study of red giants to date. We are able to approach these stars from the perspective of asteroseismology, to learn what the oscillations tell us about the internal structure of the star, and see the star as a dynamical two-body system, where gravity tells us the size and density of the objects. The use of asteroseismology to predict masses and radii for large populations of stars is a powerful and widely used tool. However, discrepancies between the asteroseismically predicted and dynamically modeled masses and radii have been found to be rather large in many cases (Gaulme, et al. 2016). To better pin down where the differences come from we are conducting a detailed study of the individual pulsation frequencies for a sample of red giants in eclipsing binary systems. For a first look, we use the MESA stellar evolution code to create a model of a star, then use GYRE to compute adiabatic frequencies from the structure given in the models. Expected frequencies are computed for models of both the asteroseismic and dynamic masses. Specific models are selected to reproduce the large frequency spacing that is observed. Both models are compared to the observed echelle diagram and predicted radii. To perform a more detailed analysis we use the astero module of MESA to run many sets models and compute many sets of frequencies while varying parameters such as mass, metallicity, overshoot, and mixing length. Individual oscillation modes are “peak-bagged” to find their exact frequency using the DIAMONDS code and then used as constraints to MESA's astero module. Here we present the first results using this method for red giants in eclipsing binaries.