Geometry effects on the formation of the hydrogen Ly-alpha line in planetary nebulae

Abstract

In order to study the effects of sphericity on the radiative transfer in the hydrogen Ly alpha line of planetary nebulae, the radiation field in this line is calculated for static pure hydrogen models with ratios of outer to inner radii’s approximately equal to 2, 4 and 8. For r/subout / r/subin ≈ 2 the transfer equation is also solved in plane parallel approximation for comparison. Both reflecting and open inner boundaries are considered. The transfer equation has been solved in the framework of the discrete space theory. In the spherical calculations the profiles of the emergent radiation are not found to be very different in their shapes (one from another) while there are large differences in the internal radiation fields. Substantial changes occur for most quantities, when the spherical approximation is replaces by the plane parallel one.