The CoRoT target HD 49933 . I. Effect of the metal abundance on the mode excitation rates
Abstract
Context. Solar-like oscillations are stochastically excited by turbulent convection at the surface layers of the stars.
Aims: We study the role of the surface metal abundance on the efficiency of the stochastic driving in the case of the CoRoT target HD 49933.
Methods: We compute two 3D hydrodynamical simulations representative - in effective temperature and gravity - of the surface layers of the CoRoT target HD 49933, a star that is rather metal poor and significantly hotter than the Sun. One 3D simulation has a solar metal abundance, and the other has a surface iron-to-hydrogen, [Fe/H], abundance ten times smaller. For each 3D simulation we match an associated global 1D model, and we compute the associated acoustic modes using a theoretical model of stochastic excitation validated in the case of the Sun and α Cen A.
Results: The rate at which energy is supplied per unit time into the acoustic modes associated with the 3D simulation with [Fe/H] = -1 is found to be about three times smaller than those associated with the 3D simulation with [Fe/H] = 0. As shown here, these differences are related to the fact that low metallicity implies surface layers with a higher mean density. In turn, a higher mean density favors smaller convective velocities and hence less efficient driving of the acoustic modes.
Conclusions: Our result shows the importance of taking the surface metal abundance into account in the modeling of the mode driving by turbulent convection. A comparison with observational data is presented in a companion paper using seismic data obtained for the CoRoT target HD 49933.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- January 2010
- DOI:
- 10.1051/0004-6361/200911867
- arXiv:
- arXiv:0910.4027
- Bibcode:
- 2010A&A...509A..15S
- Keywords:
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- convection;
- turbulence;
- stars: oscillations;
- stars: individual: HD 49933;
- Sun: helioseismology;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- corrected title &