The Pistol Star and Massive Stars in the Galactic Center

Donald F. Figer(1), Francisco Najarro(2), & Norbert Langer(3)

(1) University of California, Los Angeles, Division of Astronomy, Department of Physics & Astronomy, Los Angeles, CA 90095-1562
(2) CSIC, Instituto de Estructura de la Materia, Dpto. Fisica Molecular Serrano 121, 28006 Madrid, Spain
(3) Institut für Theoretische Physik und Astrophysik, Am Neuen Palais 10, D-14469 Potsdam, Germany

Paper: to appear in Unsolved Problems in Stellar Evolution 1998, STScI



A significant portion of the massive stars in the Galaxy are located within 50 pc of the Galactic Center. The stars have a variety of ages between 1 and 10 Myr, giving rise to Wolf-Rayet and red supergiant types. Most of these stars reside in three massive clusters: the Central Cluster, Quintuplet Cluster, and Arches Cluster. The clusters have similar masses, ~ 104 \Msun, but the first two are substantially older (3-5 Myr) than the last (1-2 Myr). This spread in age, with most other parameters being equal, gives us a unique opportunity to test models which predict massive star evolution. We discuss the content in these clusters, with a particular emphasis on how well they fit into our current understanding of stellar evolution. In particular, we discuss the Pistol Star, one of the most luminous, and, therefore, initially most massive, stars in the Galactic Center. Its evolutionary status places the star in the unstable Luminous Blue Variable stage, providing an extraordinary opportunity to test stellar evolution models for massive stars near their Eddington limits. We find a lower luminosity limit of 106.6 \Lsun, \Teff ~ 104.15 K, and a helium-enriched surface, consistent with the star's advanced evolutionary status. Our evolutionary tracks suggest an initial mass of ~ 200 \Msun and age of 1.7-2.1 Myrs. We interpret the star and its surrounding nebula as an LBV which has recently ejected large amounts of material. We expect that many of the massive stars in the Galactic Center will soon progress through an LBV stage and eventually become supernovae at a rate of ~ 1 per 20,000 years for the next several Myr.

Preprints available from the authors at , or the raw TeX (no figures) if you click here.

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