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Astron. Astrophys. 351, 519-525 (1999)


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Blue horizontal branch stars in metal-rich globular clusters

I. NGC 6388 and NGC 6441 *

S. Moehler 1, A.V. Sweigart 2 and M. Catelan ***  2

1 Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany
(ai13@sternwarte.uni-erlangen.de)
2 NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA (sweigart@bach.gsfc.nasa.gov; catelan@virginia.edu)

Received 12 April 1999 / Accepted 14 September 1999

Abstract

We report the first results of an ongoing spectroscopic survey of blue horizontal branch stars in the metal-rich ([FORMULA]) globular clusters NGC 6388 and NGC 6441. Based on data obtained with the ESO-New Technology Telescope (NTT), we provide gravities and temperatures for four stars in NGC 6388 and three stars in NGC 6441. These results are marginally inconsistent with the predictions of canonical evolutionary theory, but disagree strongly with all non-canonical scenarios that explain the sloped horizontal branches seen in the colour-magnitude diagrams of these clusters.

Key words: stars: early-type – stars: fundamental parameters – stars: horizontal-branch – Galaxy: globular clusters: individual: NGC 6388 – Galaxy: globular clusters: individual: NGC 6441

* Based on observations collected at the European Southern Observatory (ESO No 61.E-0361)
** Hubble Fellow.
*** Visiting Scientist, Universities Space Research Association.

Send offprint requests to: S. Moehler

© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999

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