Winds in Central Stars of Planetary Nebulae

Abstract

We studied five central stars of planetary nebulae with IUE high-resolution spectra to determine the wind properties of their central stars. Using the best stellar and nebular parameters, and analyzing the P Cygni profiles seen in lines of the ions C IV, N V, N IV, O V, O IV, and Si IV with the SEI method, we have obtained the following values of the mass loss rates: 3 x 10 exp -8, 2 x 10 exp -8, 3 x 10 exp -8, greater than 7 x 10 exp -11, and about 6 x 10 exp -7, for NGC 6572, IC 2149, IC 3568, LT 5, and Tc 1, respectively. The errors of these determinations are estimated to be factors of 3 in the first star, 4 in IC 2149 and IC 3568, and one order of magnitude in Tc 1. A comparison with predictions by the radiation driven theory was possible in the cases of IC 3568, Tc 1, and NGC 6572, where the mass of the central star is relatively well known. In the first and the last star, the agreement between observed and predicted mass loss rates is very good, while in Tc 1, the observed value is one order of magnitude above the predicted one. But in this star the 'observational error' is of a similar amount. We infer that our observations essentially confirm the radiation driven theory for central stars of planetary nebulae. The effect of the observed fast winds on the evolution of the central stars appears often comparable to that of the nuclear source.