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- Title
Calibrating the α parameter of convective efficiency using observed stellar properties.
- Authors
Wu, X. S.; Alexeeva, S.; Mashonkina, L.; Wang, L.; Zhao, G.; Grupp, F.
- Abstract
Context. Synthetic model atmosphere calculations are still the most commonly used tool when determining precise stellar parameters and stellar chemical compositions. Besides three-dimensional models that consistently solve for hydrodynamic processes, one dimensional models that use an approximation for convective energy transport play the major role. Aims. We use modern Balmer-line formation theory as well as spectral energy distribution (SED) measurements for the Sun and Procyon to calibrate the model parameter that describes the effciency of convection in our 1D models. Convection was calibrated over a significant range in parameter space, reaching from F-K along the main sequence and sampling the turno and giant branch over a wide range of metallicities. This calibration was compared to theoretical evaluations and allowed an accurate modeling of stellar atmospheres. Methods. We used Balmer-line fitting and SED fits to determine the convective effciency parameter α. Both methods are sensitive to the structure and temperature stratification of the deeper photosphere. Results. While SED fits do not allow a precise determination of the convective parameter for the Sun and Procyon, they both favor values significantly higher than 1.0. Balmer-line fitting, which we find to be more sensitive, suggests that the convective effciency parameter α is ≈2.0 for the main sequence and quickly decreases to ≈1.0 for evolved stars. These results are highly consistent with predictions from 3D models. While the values on the main sequence fit predictions very well, measurements suggest that the decrease of convective effciency as stars evolve to the giant branch is more dramatic than predicted by models.
- Subjects
STELLAR atmospheres; STAR formation; CONVECTIVE clouds; SPECTRAL energy distribution; GIANT stars; BALMER line
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2015, Vol 577, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201525781