The sphericity effects in the NLTE model atmospheres of hot post-AGB stars

The assumption of a plane-parallel geometry is tested for the case of NLTE model atmospheres of hot post-AGB stars. As a test sample, two stars of thi s type are chosen, namely Barnard 29 and LS 4825. It is found that the diff erences between line profiles calculated for plane-parallel and spherically symmetric atmospheres are about several percent in the centers of hydrogen Balmer and Paschen lines, and, consequently, cannot be neglected. In addit ion, LTE approximation is also checked and it is found that this assumption is completely unacceptable for the analysis of the atmospheres of hot post -AGB stars. (C) 1999 Elsevier Science B.V. All rights reserved.