abstract

A sun-like star has a number of areas where sound speed or its derivatives fluctuate quickly, such as the ionization zones of plentiful elements and the interfaces between radiative and convective regions. The discontinuity in the second derivative of the sound speed causes the sharp variations at the radiative and convective zone interfaces, while the local depression of the first adiabatic index, Γ1 = ∂ ln P, where P and ρ stand for pressure and density, respectively, causes the sharp variations in the ionization zones. In the observed frequency range, the convective core boundary signature usually becomes aliased to very close to the surface and is indistinguishable from the background smooth component. We conducted systematic research to explore and remove any potential systematic uncertainty in the glitch analysis utilizing only the stellar models and the data for the real stars (the Sun and 16 Cyg A) along with their representative models. The Helium abundance is frequently considered as one of the free parameters that are changed to get the best fit to the data when more information is available, such as stellar oscillation frequencies and other spectroscopically determined stellar observables. Although these techniques provide more accurate constraints on the initial helium abundance, our incapacity to accurately simulate a star's surface may introduce systematic mistakes. The dynamical consequences of convection are not included in normal 1D models, which only handle convection in rough approximations. This results in significant variations in the near-surface layer structure, which causes a frequency-dependent inaccuracy in the frequencies known as the surface effect. The calculated stellar characteristics may have systematic inaccuracies if the surface term is eliminated.