The sphericity effects in the NLTE model atmospheres of white dwarfs

We have calculated a sample grid of plane-parallel and spherically symmetric model atmospheres of white dwarfs for different T-eff and log g and with different helium abundances. The model atmospheres consist only of hydrogen and helium. The NLTE model atmospheres are calculated with the help of our own computer code that enables calculation of both plane-parallel and spherically symmetric model atmospheres, and consequently, an easy and reliable estimate of the sphericity effects. The sphericity effects are not drastic, but neglecting them introduces a systematic error into model atmosphere analysis.