Element settling due to the combined effects of gravity, thermal gradient, radiative acceleration and concentration gradient may lead to important abundance variations inside the stars that cannot be neglected in the computation of stellar structure. These processes were first introduced to account for abundance anomalies in `peculiar stars', but their importance in the so-called `normal' stars is now fully acknowledged, specially after the evidence of helium steeling in the Sun from helioseismology. These microscopic processes work in competition with macroscopic motions, such as rotation-induced mixing or mass loss, which increase the settling timescales. We have recently obtained clear evidence that asteroseismology of main sequence solar-type stars can give signatures of the chemical variations inside the stars and provide a better understanding of these processes.
IAU Colloq. 193: Variable Stars in the Local Group
- Pub Date:
- May 2004
- 10 pages, 2 figures, proceedings of the IAU colloquium 193 "variable stars in the local group", ed. D.W. Kurtz and K. Pollard, in press