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Preprint 11m/04

Successors of White Dwarfs - Blue Hook Stars and the Late Hot Flasher Scenario

S. Moehler (1), A.V. Sweigart (2), W.B. Landsman (2), N.J. Hammer (3), S. Dreizler (4)

(1) Institut für Theoretische Physik und Astrophysik der Universität Kiel, Olshausenstrasse 40, D-24118 Kiel, Germany
(2) NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA
(3) Institut für Astronomie und Astrophysik der Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(4) Universitäts-Sternwarte Göttingen, Geismarlandstr. 11, D-37083 Göttingen, Germany

To be published in: 14th European Workshop on White Dwarfs, eds. D. Koester, S. Moehler, ASP Conf. Ser.

Abstract. Recent UV observations of massive globular clusters show a significant population of hot stars fainter than the zero-age horizontal branch ("blue hook" stars), which cannot be explained by canonical stellar evolution. Stars which experience unusually large mass loss on the red giant branch and which subsequently undergo the helium core flash while descending the white dwarf cooling curve could populate this region. Such objects should show higher temperatures than the hottest canonical horizontal branch stars and should have helium- and carbon-rich atmospheres. As a test of this late hot flasher scenario, we have obtained and analysed medium resolution spectra of a sample of blue hook stars to derive their atmospheric parameters. While these parameters generally support the late hot flasher scenario there remain important differences between our observational results and theoretical predictions.

Preprint (130 kb PDF file including figures)

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