Fast winds in central stars of some planetary nebulae

Winds from the central stars of the planetary nebulae NGC 1535, NGC 6210, NGC 7009, IC 418, and IC 4593 have been investigated with high-resolution IUE spectra. All these stars present P Cygni profiles in some of the following lines: N V 1240, O IV 1342, O V 1371, Si IV 1397, C IV 1549, and N IV 1719 A. These profiles have been analyzed with the SEI method developed by Lamers et al. (1987). The mass-loss rates of the winds are found to be 1.4 x 10 to the -9th, 2.2 x 10 to the -9th, 2.8 x 10 to the -9th, 6.3 x 10 to the -9th, and 4.2 x 10 to the -8th solar mass/yr for the above stars, respectively. Despite all efforts made in order to reach the maximum accuracy, the uncertainty of these determinations remains in some cases quite large. Nevertheless, it is possible to show that the mechanism producing the winds is likely to be the radiation pressure. 35 refs.