1. Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université Montpellier II, Montpellier, France 2 Département de physique, Université de Montréal, Montréal, Canada

2. Am stars Montréal Models Results Surface abundances of Am stars as a constraint on rotational mixing

3. Statistics suggest all non-magnetic stars with V<80 km/s Recent observations in open clusters Mg~ normal Al, Si, S: ~normal or slight overabundance Ca ~ normal or underabundant Ni and Fe overabundant Am Stars

4. Burger’s equations 2 equations for each species (28 in the code) Solved for each mesh points (~1500) and at each time step (~1000)

5. Radiative accelerations 1.5 GigaBytes of data ; OPAL (1996) –Integration over fraction of photons given to i at each frequency Expression used in evolution calculations

6. Mixing model Simplest version of the turbulent diffusion coefficient obtained from self-consistent treatment of the meridional circulation following Zahn (1992) Mixing added to the code as a diffusion process with a parametric mixing diffusion coefficient:

7. Mixing model Simplest version of the turbulent diffusion coefficient obtained from self-consistent treatment of the meridional circulation following Zahn (1992) Mixing added to the code as a diffusion process with a parametric mixing diffusion coefficient:

8. Computed models Models of 1.7 and 1.9 solar masses With mixing coefficient corresponding to surface velocity of 50 km/s (V50), 15 km/s (V15), and 5 km/s (V5, V5N) Richer et al. (2000) 1.9R300-2 and 1.9R1k- 2 models

9. Effective temperature and surface gravity evolution 1.9 1.7

10. Radiative acceleration in the 1.9 solar masses models

11. Abundance profiles at 800 Myr Model 1.9V5 r 1 0

12. Abundance evolution in the 1.9 solar masses models

13. The Praesepe star HD73045

15. Conclusion In the mixing model the turbulence seems to be too strong to allow the Am phenomenon to occur at a reasonable velocity Need of self-consistent abundance determination for a lot of chemical species in stars of different ages and metallicity