A prescription for the asteroseismic surface correction

Abstract

In asteroseismology, the surface effect is a disparity between the observed and the modelled oscillation frequencies. It originates from improper modelling of the surface layers in stars with solar-like oscillations. Correcting the surface effect usually requires using functions with free parameters, which are conventionally fitted to the observed frequencies. On the basis that the correction should vary smoothly across the H-R diagram, we parameterize it as a simple function of three stellar surface properties: surface gravity, effective temperature, and metallicity. We determine this function by fitting stars ranging from main-sequence dwarfs to red-giant-branch stars. The absolute amount of the surface correction increases with surface gravity, but the ratio between it and ν max decreases. Applying the prescription has an advantage of eliminating unrealistic surface correction, which improves parameter estimations with stellar modelling. Using two open clusters, we found that adopting the prescription can help reduce the scatter of the modelderived ages for each star in the same cluster. For an application, we provide a new revision for the ∆ν scaling relation, using our prescription to account for the surface effect in models. The values of the correction factor, f ∆ν , are up to 2% smaller than those determined without the surface effect considered, suggesting decreases of up to 4% in asteroseismic scaling radii and up to 8% in asteroseismic scaling masses. This revision brings the asteroseismic properties into agreement with those determined from eclipsing binaries. Finally, the new correction factor and the stellar models with the corrected frequencies are made publicly available.

Asteroseismic Modeling of 1153 Kepler Red Giant Branch Stars: Improved Stellar Parameters with Gravity-mode Period Spacings and Luminosity Constraints

“…The surface term is caused by incorrect modeling of the nearsurface layers in stellar code. Given that the properties near-surface layers largely correlate to global parameters, the surface term is expected to vary smoothly as a function of effective temperature, surface gravity, and metallicity (Trampedach et al 2017;Compton et al 2018;Jørgensen et al 2020;Ong et al 2021;Li Y. et al 2022b). The star sample in this work makes it possible to systematically study the surface term and its dependencies on surface features in a wide parameter range.…”

Revisiting the Red Giant Branch Hosts KOI-3886 and ι Draconis. Detailed Asteroseismic Modeling and Consolidated Stellar Parameters

“…mode frequencies in seismic modeling in general. The determination of methods by which it may be corrected for remains an area of active research (e.g., Ball & Gizon 2014;Compton et al 2018;Nsamba et al 2018;Li et al 2022b). A correction for the surface term in red giants requires special treatment, owing to the presence of mixed modes (Ball et al 2018;Ong et al 2021b), and estimates of some of the properties of red giants have been shown to be potentially sensitive to methodological decisions as to how this correction is to be performed (e.g., Ong et al 2021a).…”