On the structure of the Sun and alpha Centauri A and B in the light of seismic and non-seismic constraints

TL;DR

This study investigates the internal structure and age of the Sun and alpha Centauri A and B using seismic oscillation data, highlighting discrepancies in age estimates and the potential for more precise frequency measurements.

Contribution

The paper introduces a combined seismic and non-seismic modeling approach to determine stellar ages and masses, addressing inconsistencies in age estimates from small frequency separations.

Findings

The Sun's age is estimated at 4.9-5.0 Gyr from seismic data.

Alpha Centauri A and B show conflicting age estimates from different seismic indicators.

Model fits suggest slight mass adjustments and an age of about 5.2-5.3 Gyr for the system.

Abstract

The small separation (delta nu 01, delta nu 02 and delta nu 13) between the oscillations with low degree l is dependent primarily on the sound speed profile within the stellar core, where nuclear evolution occurs. The detection of such oscillations for a star offers a very good opportunity to determine the stage of its nuclear evolution, and hence its age. In this context, we investigate the Sun and alpha Cen A and B. For alpha Cen A and B, each of the small separations delta nu 01, delta nu 02 and delta nu 13 gives a different age. Therefore, in our fitting process, we also employ the second difference, defined as nu n2 - 2 nu n1 + nu n0, which is 2 delta nu 01- delta nu 02. In addition to this, we also use frequency ratio (nu n0/ nu n2). For the Sun, these expressions areequivalent and give an age of about 4.9-5.0 Gyr. For alpha Cen A and B, however, the small separation and the second difference give very different ages. This conflict may be solved by the detection of oscillation frequencies that can be measured much more precisely than the current frequencies. When we fit the models to the observations, we find (i) Z 0=0.020, t=3.50 Gyr and M B=1.006 Msun from the small separations delta nu 01, delta nu 02 and delta nu 13 of alpha Cen B; and (ii) a variety of solutions from the non-seismic constraints and delta nu 02 of alpha Cen A and B, in which the masses of alpha Cen A and B are slightly modified and the age of the system is about 5.2-5.3 Gyr. For Z=0.025, the closest masses we find to the observed masses are M B=0.922 Msun and M A=1.115 Msun.The differences between these masses and the corresponding observed masses are about 0.01 Msun.