Is there a unique asteroseismic interior model for the solar-like oscillating KIC 7747078?

Abstract

Asteroseismology provides a direct observational window into the structure and evolution of stars. While spectroscopic and photometric methods only provide information about the surface properties of stars, asteroseismology, through the analysis of oscillation frequencies, offers comprehensive information about the deep stellar interior as well as the surface. The scattering of effective temperature (Teff) determined from the spectrum and degeneracy in the Hertzsprung Russell diagram poses challenges in developing a unique interior model for a single star. Although observational asteroseismic data partially lift this degeneracy, the best model that meets all asteroseismic constraints is not obtained. Most models reported in the literature typically address the large separation Dnu constraint between oscillation frequencies, which is a critical issue, especially in post main sequence stars. Reference frequencies, influenced by helium ionisation zone induced glitches in oscillation frequencies, are instrumental in refining models. Using the high metallicity derived from the colors of the Kepler Legacy star KIC 7747078, we obtain the masses of models M as 1.208 Msun and 1.275 Msun using the reference frequencies and individual frequencies as constraints, respectively. By applying the chi2 method using these reference frequencies, Dnu, and surface metallicity determined from the spectrum, we develop a unique star model with a mass of 1.171 pm 0.019 Msun, a radius of 1.961 pm 0.011 Rsun, an effective temperature of 5993 K, an initial metallicity of 0.0121, and an age of 5.15 pm 0.29 Gyr. A significant advantage of this method is that Teff emerges as an output, not a constraint. The mixed mode oscillation frequencies of this model align well with the observations.