Asteroseismic analysis of solar-mass subgiants KIC 6442183 and KIC 11137075 observed by Kepler

TL;DR

This study uses Kepler data to perform detailed asteroseismic analysis of two solar-mass subgiants, deriving stellar parameters and demonstrating the use of mode inertias and frequency differences to constrain stellar models.

Contribution

It provides a detailed asteroseismic analysis of two subgiants, including mode frequency extraction and model constraints using mode inertias and frequency differences.

Findings

Estimated global asteroseismic parameters for both stars.

Derived stellar masses, radii, and ages with uncertainties.

Showed that mode inertias and frequency differences effectively constrain stellar models.

Abstract

Asteroseismology provides a powerful way to constrain stellar parameters. Solar-like oscillations have been observed on subgiant stars with the \emph{Kepler\/} mission. The continuous and high-precision time series enables us to carry out a detailed asteroseismic study for these stars. We carry out data processing of two subgiants of spectral type G: KIC 6442183 and KIC 11137075 observed with the \emph{Kepler} mission, and perform seismic analysis for the two evolved stars. We estimate the values of global asteroseismic parameters: $\Delta\nu=64.9\pm 0.2 $ $\mu$Hz and $\nu_{\rm max}=1225 \pm 17$ $\mu$Hz for KIC 6442183, $\Delta\nu=65.5\pm 0.2 $ $\mu$Hz and $\nu_{\rm max}=1171 \pm 8$ $\mu$Hz for KIC 11137075, respectively. In addition, we extract the individual mode frequencies of the two stars. We compare stellar models and observations, including mode frequencies and mode inertias. The mode inertias of mixed modes, which are sensitive to the stellar interior, are used to constrain stellar models. We define a quantity $d\nu_{\rm m-p}$ that measures the difference between the mixed modes and the expected pure pressure modes, which is related to the inertia ratio of mixed modes to radial modes. Asteroseismic together with spectroscopic constraints provide the estimations of the stellar parameters: $M = 1.04_{-0.04}^{+0.01} M_{\odot}$, $R = 1.66_{-0.02}^{+0.01} R_{\odot}$ and $t=8.65_{-0.06}^{+1.12}$ Gyr for KIC 6442183, and $M = 1.00_{-0.01}^{+0.01} M_{\odot}$, $R = 1.63_{-0.01}^{+0.01} R_{\odot}$ and $t=10.36_{-0.20}^{+0.01}$ Gyr for KIC 11137075. Either mode inertias or $d\nu_{\rm m-p}$ could be used to constrain stellar models.