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                              G C N E W S
                             * Newsflash *

            - The Newsletter for Galactic Center Research -

gcnews@mpifr-bonn.mpg.de             http://www.mpifr-bonn.mpg.de/gcnews
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Vol. 12, No. 17                                              Nov 13, 2000


Recently submitted papers:
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1) New Results on the Helium Stars in the Galactic Center Using BEAR 
   Spectro-Imagery (Paumard et al., A&A)
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Email    : paumard@iap.fr
Title    : New Results on the Helium Stars in the Galactic Center Using 
           BEAR Spectro-Imagery
Author(s): T. Paumard(1), J.P. Maillard(1), M. Morris(2), F. Rigaut(3)
Institute: (1) Institut d'Astrophysique de Paris (CNRS), 98b Blvd 
           Arago, 75014 Paris, France (2) University of California, Los 
           Angeles, Div. of Astronomy, Dept of Physics and Astronomy, 
           Los Angeles, CA 90095-1562, USA (3) Gemini North 
           Headquarter, Hilo, HI 96720, USA
Paper    : A&A, accepted
EPrint   : astro-ph/0011215

Abstract:
Integral field spectroscopy of the central parsec of the Galactic 
Center was obtained at 2.06 micron using BEAR, an imaging Fourier 
Transform Spectrometer, at a spectral resolution of 74 km s^-1. Sixteen 
stars were confirmed as `` helium stars'' by detecting the \ionHeI 
2.058 micron line in emission, providing a homogeneous set of fully 
resolved line profiles. These observations allow us to discard some of 
the earlier detections of such stars in the central cluster and to add 
three new stars. The sources detected in the BEAR data were compared 
with adaptive optics images in the K band to determine whether the 
emission was due to single stars. Two sub-classes of almost equal 
number are clearly identified from the width of their line profiles, 
and from the brightness of their continuum. The first class is 
characterized by very broad line profiles (FWHM 1000 km s^-1) and by 
their relative faintness. The other, brighter in K by an average factor 
of 9, has a much narrower emission component of width 200 km s^-1. Most 
of the emission lines show a P Cygni profile. From these results, we 
propose that the latter group is formed of stars in or near the LBV 
phase, and the other one of stars at the WR stage. The division into 
two groups is also shown by their spatial distribution, with the 
narrow-line stars in a compact central cluster (\objectIRS 16) and the 
other group distributed at the periphery of the central cluster of hot 
stars. In the same data cube, streamers of interstellar helium gas are 
also detected. The helium emission traces the densest parts of the SgrA 
West Mini-Spiral. Several helium stars have a radial velocity 
comparable to the velocity of the interstellar gas in which they are 
embedded. In the final discussion, all these findings are examined to 
present a possible scenario for the formation of very massive stars in 
the exceptional conditions of the vicinity of the central Black Hole.
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