Heavy Element Diffusion in Metal Poor Stars

Details Heavy Element Diffusion in Metal Poor Stars Heavy Element Diffusion in Metal Poor Stars

2001-08-07

arxiv.org/abs/astro-ph/0108119v1

Astrophys.J.562:521-527,2001

Astronomy and Astrophysics

Astrophysics

to appear in ApJ; 11 pages

Scientific paper

10.1086/323872

Stellar evolution models which include the effect of helium and heavy element diffusion have been calculated for initial iron abundances of [Fe/H] = -2.3, -2.1, -1.9 and -1.7. These models were calculated for a large variety of masses and three separate mixing lengths, \alpha = 1.50, 1.75 and 2.00 (with \alpha = 1.75 being the solar calibrated mixing length). The change in the surface iron abundance for stars of different masses was determined for the ages 11, 13 and 15 Gyr. Iron settles out of the surface convection zone on the main sequence; this iron is dredged back up when the convection zone deepens on the giant branch. In all cases, the surface [Fe/H] abundance in the turn-off stars was at least 0.28 dex lower than the surface [Fe/H] abundance in giant-branch stars of the same age. However, recent high dispersion spectra of stars in the globular cluster NGC 6397 found that the turn-off and giant branch stars had identical (within a few percent) iron abundances of [Fe/H] =-2.03 (Gratton et al. 2001). These observations prove that heavy element diffusion must be inhibited in the surface layers of metal-poor stars. When diffusion is inhibited in the outer layers of a stellar model, the predicted temperatures of the models are similar to models evolved without diffusion, while the predicted lifetimes are similar to stars in which diffusion is not inhibited. Isochrones constructed from the models in which diffusion is inhibited fall half-way between isochrones without diffusion, and isochrones with full diffusion. As a result, absolute globular cluster ages which are based upon the absolute magnitude of the turn-off are 4% larger than ages inferred from full diffusion isochrones, and 4% smaller than ages inferred from no diffusion isochrones.

Affiliated with

Also associated with

No associations

Rating

Heavy Element Diffusion in Metal Poor Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Heavy Element Diffusion in Metal Poor Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heavy Element Diffusion in Metal Poor Stars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-326658