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Astron. Astrophys. 325, 700-708

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

F. Najarro1, A. Krabbe2, R. Genzel2, D. Lutz2, R.P. Kudritzki1,3, and D.J. Hillier4

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

Received 7 January 1997 / Accepted 24 March 1997


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 (V FORMULA FORMULA 300 to 1000 km s-1). The effective temperatures of the objects range from 17,000 K to 30,000 K with corresponding stellar luminosities of 1 to FORMULA L FORMULA . Strongly enhanced helium abundances (N/N>.5) 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

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998