Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2011-02-09
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
Accepted for publication by A&A
Scientific paper
Context. Abundance anomalies have been observed in field sdB stars and in nearly all Horizontal Branch (HB) stars of globular clusters with Teff > 11 000K whatever be the cluster metallicity. Aims. The aim is to determine the abundance variations to be expected in sdB stars and in HB stars of metallicities Z \geq 0.0001 and what observed abundances teach us about hydrodynamical processes competing with atomic diffusion. Methods. Complete stellar evolution models, including the effects of atomic diffusion and radiative acceleration, have been computed from the zero age main-sequence for metallicities of Z0 = 0.0001, 0.001, 0.004 and 0.02. On the HB the masses were selected to cover the Teff interval from 7000 to 37000K. Some 60 evolutionary HB models were calculated. The calculations of surface abundance anomalies during the horizontal branch depend on one parameter, the surface mixed mass. Results. For sdB stars with Teff < 37000K and for HB stars with Teff > 11 000K in all observed clusters, independent of metallicity, it was found that most observed abundance anomalies (even up to ~ x 200) were compatible, within error bars, with expected abundances. A mixed mass of ~1.E-7 M\odot was determined by comparison with observations. Conclusions. Observations of globular cluster HB stars with Teff > 11 000K and of sdB stars with Teff < 37 000K suggest that most observed abundance anomalies can be explained by element separation driven by radiative acceleration occuring at a mass fraction of ~1.E-7 M\odot. Mass loss or turbulence appear to limit the separation between 1.E-7 M\odot and the surface.
Michaud Georges
Richard Olivier
Richer Jacques
No associations
LandOfFree
Horizontal Branch evolution, metallicity and sdB 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 Horizontal Branch evolution, metallicity and sdB stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Horizontal Branch evolution, metallicity and sdB stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-693639