Hot Stars in Globular Cluster - A Spectroscopist's View

Abstract

Globular clusters are ideal laboratories to study the evolution of low-mass stars. In this work we concentrate on three types of hot stars observed in globular clusters: horizontal branch stars, UV bright stars, and white dwarfs. After providing some historical background and information on gaps and blue tails we discuss extensively hot horizontal branch stars in metal-poor globular clusters, esp. their abundance anomalies and the consequences for the determination of their atmospheric parameters and evolutionary status. Hot horizontal branch stars in metal-rich globular clusters are found to form a small, but rather inhomogeneous group that cannot be explained by one evolutionary scenario. Hot UV bright stars show a lack of classic post-AGB stars that may explain the lack of planetary nebulae in globular clusters. Finally we discuss first results of spectroscopic observations of white dwarfs in globular clusters.

20 pages, 4 figures (fully resolved PS file of Fig. 1 available at http://a400.sternwarte.uni-erlangen.de/ftp/MOEHLER/ASTRO-PH/FIG1.PS) Invited Review, to appear in the October 2001 issue of PASP