Non-LTE Model Atmosphere Analyses of Faint PN Central Stars Observed with Keck HIRES

Abstract

We are engaged in using the HIRES echelle spectrograph (Vogt et al. 1994) on the 10 m Keck I Telescope to significantly increase the number of central stars of planetary nebulae (CSPN) studied spectroscopically at high resolution and signal-to-noise ratio. With Keck we are able to extend our previous work (Méndez et al. 1988, 1992; McCarthy 1988) to much fainter magnitudes. In short, comparisons of the observed HI Balmer, HeI, and HeII line profiles to the Munich grid of plane-parallel non-LTE model atmosphere line profiles provide distance- and nebula-independent determinations of CSPN effective temperature, surface gravity, and helium abundance. For CSPN showing wind emission, the comparisons are made to new “unified” models (reviewed by Kudritzki et al., this meeting) which include radiation-driven winds. The first results of this on-going program are shown below.