Massive Stars in the Arches Cluster

We present and use new spectra and narrow-band images, along with previouslypublished broad-band images, of stars in the Arches cluster to extractphotometry, astrometry, equivalent width, and velocity information. The dataare interpreted with a wind/atmosphere code to determine stellar temperatures,luminosities, mass-loss rates, and abundances. We have doubled the number ofknown emission-line stars, and we have also made the first spectroscopicidentification of the main sequence for any population in the Galactic Center.We conclude that the most massive stars are bona-fide Wolf-Rayet (WR) stars andare some of the most massive stars known, having M_{initial} > 100 Msun, andprodigious winds, Mdot > 10^{-5} Msun yr^{-1}, that are enriched with heliumand nitrogen; with these identifications, the Arches cluster contains about 5%of all known WR stars in the Galaxy. We find an upper limit to the velocitydispersion of 22 kms^{-1}, implying an upper limit to the cluster mass of7(10^4) Msun within a radius of 0.23 pc; we also estimate the bulk heliocentricvelocity of the cluster to be v_{cluster,odot} approximately +95 kms^{-1}