Stellar models typically use the mixing length approximation as a way to implement convection in a simplified manner. While conventionally the value of the mixing length parameter, α, used is the solar calibrated value, many studies have shown that other values of α are needed to properly model stars. This uncertainty in the value of the mixing length parameter is a major source of error in stellar models and isochrones. Using asteroseismic data, we determine the value of the mixing length parameter required to properly model a set of about 450 stars ranging in log g, T eff , and [Fe/H]. The relationship between the value of α required and the properties of the star is then investigated. For Eddington atmosphere, non-diffusion models, we find that the value of α can be approximated by a linear model, in the form of α/α ⊙ = 5.426 − 0.101 log(g)− 1.071 log(T eff )+ 0.437([Fe/H]). This process is repeated using a variety of model physics as well as compared to previous studies and results from 3D convective simulations.

The scaling relations that relate the average asteroseismic parameters ∆ν and ν max to the global properties of stars are used quite extensively to determine stellar properties. While the ∆ν scaling relation has been examined carefully and the deviations from the relation have been well documented, the ν max scaling relation has not been examined as extensively. In this paper we examine the ν max scaling relation using a set of stellar models constructed to have a wide range of mass, metallicity, and age. We find that as with ∆ν, ν max does not follow the simple scaling relation. The most visible deviation is because of a mean molecular weight term and a Γ 1 term that are commonly ignored. The remaining deviation is more difficult to address. We find that the influence of the scaling relation errors on asteroseismically derived values of log g are well within uncertainties. The influence of the errors on mass and radius estimates is small for main sequence and subgiants, but can be quite large for red giants.

Core overshoot is a large source of uncertainty in constructing stellar models. Whether the amount of overshoot is constant or mass dependent is not completely known, even though models sometimes assume a mass-based trend. In this work we use asteroseismic data from stars observed by Kepler to investigate the relationship between various stellar properties and the amount of overshoot needed to properly model a given star. We find a strong positive trend between stellar mass and overshoot amount for stars between 1.1 and 1.5 , with a slope of 0.89. Additionally, we investigate how inferred stellar properties change as a function of overshoot. Our model grids show that the inferred stellar mass and radius can vary by as much as 14% and 6%, respectively, depending on the extent of overshoot. This mass spread results in a commensurate spread in the ages.

The Hyades open cluster was targeted during Campaign 4 (C4) of the NASA K2 mission, and short-cadence data were collected on a number of cool main-sequence stars. Here, we report results on two F-type stars that show detectable oscillations of a quality that allows asteroseismic analyses to be performed. These are the first ever detections of solar-like oscillations in main-sequence stars in an open cluster.

Asteroseismology of solar-like oscillators often relies on the comparisons between stellar models and stellar observations in order to determine the properties of stars. The values of the global seismic parameters, ν max (the frequency where the smoothed amplitude of the oscillations peak) and ∆ν (the large frequency separation), are frequently used in grid-based modeling searches. However, the methods by which ∆ν is calculated from observed data and how ∆ν is calculated from stellar models are not the same. Typically for observed stars, especially for those with low signal-to-noise data, ∆ν is calculated by taking the power spectrum of a power spectrum, or with autocorrelation techniques. However, for stellar models, the actual individual mode frequencies are calculated and the average spacing between them directly determined. In this work we try to determine the best way to combine model frequencies in order to obtain ∆ν that can be compared with observations. For this we use stars with high signal-to-noise observations from Kepler as well as simulated TESS data of Ball et al. (2018). We find that when determining ∆ν from individual mode frequencies the best method is to use the = 0 modes with either no weighting or with a Gaussian weighting around ν max .