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Hot stars in the Galactic Center

Published online by Cambridge University Press:  25 May 2016

Andreas Eckart ,
Thomas Ott ,
Reinhard Genzel  and
Dieter Lutz
Andreas Eckart
Affiliation:
Max Planck Institut für extraterrestrische Physik, D-85740, Garching, Germany
Thomas Ott
Affiliation:
Max Planck Institut für extraterrestrische Physik, D-85740, Garching, Germany
Reinhard Genzel
Affiliation:
Max Planck Institut für extraterrestrische Physik, D-85740, Garching, Germany
Dieter Lutz
Affiliation:
Max Planck Institut für extraterrestrische Physik, D-85740, Garching, Germany

Abstract

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The central parsec of our Galaxy is powered by a cluster of young massive hot stars which formed a few million years ago. Within that cluster the seven most luminous (L >105.75 L⊙) and moderately hot (T < 104.5 K) blue supergiants contribute half of the ionizing luminosity of that region. These stars probably formed when a dense cloud fell into the center < 107 years ago, was highly compressed there, and became gravitationally unstable. Over six years of high spatial resolution, near-infrared imaging and spectroscopy have made it possible to carry out a detailed investigation of the stars in the central cluster and its enclosed mass. As one result of a detailed variability study of the central cluster stars we found that the bright He I star IRS 16SW is a short-period variable with a period of ∼9.72 days. It is most likely an eclipsing binary with a lower mass limit of 100 solar masses. Line of sight velocities and proper motions have been measured for these hot stars (as well as ∼200 other stars) down to separations of less than five light days from the compact radio source Sgr A* at the dynamic center of the Milky Way. These confirmed measurements imply the presence of a central dark mass of 2.6 × 106 solar masses. The dark mass at the center of the Milky Way is currently the most compelling case for a massive black hole. Simple physical considerations show that this dark mass cannot consist of a stable cluster of stars, stellar remnants, substellar condensations or a degenerate gas of elementary particles but that at least 103 to 105 solar masses must be in the form of a massive black hole associated with Sgr A* itself.

Type
Part 4. Wolf-Rayet stars and other hot massive stars in the Galactic Center and in Local Group giant H II regions (individual stars)
Information
Symposium - International Astronomical Union , Volume 193: Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies , 1999 , pp. 449 - 458
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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