Evolution of Hot Subdwarfs - An Empirical Approach

Abstract

Spectral analysis has been making rapid progress in the recent past. On the side of the theory, NLTE-model atmospheres plus NLTE line formation for hot stars have to be mentioned, and also the LTE metal line blanketed atmospheres. On the side of the observations, the role of the IUE telescope as a spectrophotometer has to be stressed, and the great impact of the ESO CASPEC instrument. The quality of the quantitative analyses is such that it may yield narrow constraints which allow to define the evolutionary state of the class of stars under consideration. The class of stars we are dealing with are the hot subdwarfs. How they are related to the central stars of planetary nebulae, will be shown at the end of this talk.