Helioseismology and the solar age

The problem of measuring the solar age by means of helioseismology has been recently revisited by Guenther & Demarque (1997) and by Weiss & Schlattl (1998). Different best values for tseis and different assessment of the uncertainty resulted from these two works. We show that depending on the way seismic data are used, one may obtain tseis ≈ 4.6Gy close to the age of the oldest meteorites, tmet = 4.57Gy, like in the first paper, or above 5 Gy like in the second paper. The discrepancy in the seismic estimates of the solar age may be eliminated by assuming higher than the standard metal abundance and/or an upward revision of the opacities in the solar radiative interior. We argue that the most accurate and robust seismic measure of the solar age are the small frequency separations, D`,n = νl,n − ν`+2,n−1, for spherical harmonic degrees ` = 0, 2 and radial orders n `. The seismic age inferred by minimization of the sum of squared differences between the model and the solar small separations is tseis = 4.66 ± 0.11Gy, a number consistent with meteoritic data. Our analysis supports earlier suggestions of using small frequency separations as stellar age indicators.