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Astron. Astrophys. 325, 700-708 (1997)

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Quantitative spectroscopy of the He I cluster in the Galactic center *

F. Najarro 1, A. Krabbe 2, R. Genzel 2, D. Lutz 2, R.P. Kudritzki 1, 3 and D.J. Hillier 4

1 Institut für Astronomie und Astrophysik der Universität München, Scheinerstr. 1, D-81679 München, Germany
2 Max-Planck-Institut für extraterrestrische Physik, D-85740 Garching bei München, Germany
3 Max-Planck-Institut für Astrophysik, D-85740 Garching bei München, Germany
4 Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, USA

Received 7 January 1997 / Accepted 24 March 1997

Abstract

We present first results on quantitative infrared spectroscopy of the brightest He I emission line stars in the Galactic center. The observed He I and H broad emission lines are caused by extremely strong stellar winds [FORMULA] 5 to 80 [FORMULA] with relatively small outflow velocities ([FORMULA] [FORMULA] 300 to 1000 [FORMULA]). The effective temperatures of the objects range from 17,000 K to 30,000 K with corresponding stellar luminosities of 1 to [FORMULA]. Strongly enhanced helium abundances [FORMULA] are found. These results indicate that the He I emission line stars are evolved blue supergiants close to the evolutionary stage of Wolf-Rayet stars. They power the central parsec and belong to a young stellar cluster of massive stars which formed a few million years ago.

Key words: stars: early-type – stars: mass-loss – stars: supergiants – stars: emission-line – Galaxy: center – infrared: stars

* Based on observations collected at the European Southern Observatory at La Silla, Chile

Send offprint requests to: F. Najarro

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

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