SIMBAD references

From detailed 2-dimensional numerical radiation hydrodynamics calculations of time-dependent compressible convection we have obtained the thermal structure of the convective surface layers of DA white dwarfs with effective temperatures near the blue edge of the ZZ Ceti instability strip. Synthetic line profiles of H_β and the red wing of L_α (including the very temperature sensitive satellite absorption features) computed from two representative inhomogeneous hydrodynamical models (T_eff=12200K, 12600K; log g=8.0) are compared with the spectra resulting from different plane-parallel model atmospheres. We find that it is possible to represent a given inhomogeneous atmosphere by a spectroscopically equivalent 1D model, constructed to have the same frequency-integrated radiative flux as the respective 2D hydrodynamical model at all depths. Synthetic spectra computed from this representative 1D model are almost indistinguishable from the horizontally averaged 2D synthetic spectra of the corresponding inhomogeneous model. We conclude that in the investigated range of effective temperature (probably even for the whole range of convective DAs), spectroscopic analysis based on appropriate 1D atmospheres is almost unaffected by systematic errors associated with non-linear flux variations due to the substantial thermal inhomogeneities generated by photospheric convection in these stars. This work provides the basis for a well defined comparison between 2D or 3D hydrodynamical convection models and 1D standard mixing length models.