Slowing down atomic diffusion in subdwarf B stars: mass loss or turbulence?
Article first published online: 9 SEP 2011
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Monthly Notices of the Royal Astronomical Society
Volume 418, Issue 1, pages 195–205, November 2011
How to Cite
Hu, H., Tout, C. A., Glebbeek, E. and Dupret, M.-A. (2011), Slowing down atomic diffusion in subdwarf B stars: mass loss or turbulence?. Monthly Notices of the Royal Astronomical Society, 418: 195–205. doi: 10.1111/j.1365-2966.2011.19482.x
- Issue published online: 10 NOV 2011
- Article first published online: 9 SEP 2011
- Accepted 2011 July 20. Received 2011 July 19; in original form 2011 June 14
- methods: numerical;
- stars: chemically peculiar;
- stars: evolution;
- stars: mass-loss
Subdwarf B (sdB) stars show chemical peculiarities that cannot be explained by diffusion theory alone. Both mass loss and turbulence have been invoked to slow down atomic diffusion in order to match observed abundances. The fact that some sdB stars show pulsations give upper limits on the amount of mass loss and turbulent mixing allowed. Consequently, non-adiabatic asteroseismology has the potential to decide which process is responsible for the abundance anomalies. We compute for the first time seismic properties of sdB models with atomic diffusion included consistently during the stellar evolution. The diffusion equations with radiative forces are solved for H, He, C, N, O, Ne, Mg, Fe and Ni. We examine the effects of various mass-loss rates and mixed surface masses on the abundances and mode stability. It is shown that the mass-loss rates needed to simulate the observed He abundances () are not consistent with observed pulsations. We find that for pulsations to be driven the rates should be . On the other hand, weak turbulent mixing of the outer 10−6 M⊙ can explain the He abundance anomalies while still allowing pulsations to be driven. The origin of the turbulence remains unknown but the presence of pulsations gives tight constraints on the underlying turbulence model.