Issue |
A&A
Volume 463, Number 1, February III 2007
|
|
---|---|---|
Page(s) | 297 - 308 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20041953 | |
Published online | 20 November 2006 |
Excitation of solar-like oscillations across the HR diagram
1
Observatório Astronómico UC, Coimbra, Portugal e-mail: Reza.Samadi@obspm.fr
2
Observatoire de Paris, LESIA, CNRS UMR 8109, 92195 Meudon, France
3
Center for Turbulence Research, Stanford University NASA Ames Research Center, Moffett Field, USA
4
Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Cotter Road, Weston ACT 2611, Australia
5
Department of Physics and Astronomy, Michigan State University, Lansing, USA
6
Niels Bohr Institute for Astronomy Physics and Geophysics, Copenhagen, Denmark
Received:
6
September
2006
Accepted:
14
November
2006
Aims.We extend semi-analytical computations of excitation rates for solar oscillation modes to those of other solar-like oscillating stars to compare them with recent observations
Methods.Numerical 3D simulations of surface convective zones of several solar-type
oscillating stars are used to characterize the turbulent spectra as well as to constrain the convective
velocities and turbulent entropy fluctuations in the uppermost part of the convective zone of such stars.
These constraints, coupled with a theoretical model for stochastic excitation, provide
the rate at which energy is injected into the p-modes by turbulent convection.
These energy rates are compared with those derived directly from the 3D simulations.
Results.The excitation rates obtained from the 3D simulations are systematically lower than those computed from the semi-analytical excitation model.
We find that , the
maximum, scales as
where s is the slope of
the power law and L and M are the mass and luminosity of the 1D stellar model built consistently with the associated 3D simulation.
The slope is found to depend significantly on the adopted
form of
, the eddy time-correlation; using a Lorentzian,
,
results in
, whereas a Gaussian,
, gives
.
Finally, values of Vmax, the maximum in the mode velocity, are estimated from
the computed power laws for
and
we find that
increases as
.
Comparisons with the currently available ground-based observations show that
the computations assuming a Lorentzian
yield a slope, sv, closer to the observed one
than the slope obtained when assuming a Gaussian. We show that the
spatial resolution of the 3D simulations must be high enough to
obtain accurate computed energy rates.
Key words: convection / turbulence / Sun: oscillations / Hertzsprung-Russell (HR) and C-M / stars: variables: general / methods: numerical
© ESO, 2007
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