---
author:
- 'S. Moehler'
- 'A.V. Sweigart'
- 'W.B. Landsman'
- 'N.J. Hammer'
- 'S. Dreizler'
date: 'Received 14 October 2003, accepted 4 November 2003'
title: 'Spectroscopic Analyses of the Blue Hook Stars in NGC 2808: A More Stringent Test of the Late Hot Flasher Scenario[^1] '
---

Introduction
============

Low-mass stars burning helium in a core of about 0.5  and hydrogen in a shell populate a roughly horizontal region in the colour-magnitude diagrams of globular clusters, which has earned them the name “horizontal branch" (HB) stars. The Galactic globular clusters show a great variety in horizontal branch morphology, i.e., in the temperature distribution of their HB stars. The temperature of an HB star depends – at a given metallicity – on the mass of its hydrogen envelope, with the hottest or extreme HB (EHB) stars ([$ {\rm T_{eff}}$]{} $>$ 20,000 K) having extremely thin $\lesssim$0.01) envelopes. The increase in the bolometric correction with increasing temperature turns the blue HB into a vertical blue tail in optical colour-magnitude diagrams with the faintest blue tail stars being the hottest and least massive (see Fig. \[cmd\] for a prominent example of a blue tail). It is still unclear how some stars 