Massive Stars in the Arches Cluster

Abstract

We present and use new spectra and narrow-band images, along with previously\npublished broad-band images, of stars in the Arches cluster to extract\nphotometry, astrometry, equivalent width, and velocity information. The data\nare interpreted with a wind/atmosphere code to determine stellar temperatures,\nluminosities, mass-loss rates, and abundances. We have doubled the number of\nknown emission-line stars, and we have also made the first spectroscopic\nidentification of the main sequence for any population in the Galactic Center.\nWe conclude that the most massive stars are bona-fide Wolf-Rayet (WR) stars and\nare some of the most massive stars known, having M_{initial} > 100 Msun, and\nprodigious winds, Mdot > 10^{-5} Msun yr^{-1}, that are enriched with helium\nand nitrogen; with these identifications, the Arches cluster contains about 5%\nof all known WR stars in the Galaxy. We find an upper limit to the velocity\ndispersion of 22 kms^{-1}, implying an upper limit to the cluster mass of\n7(10^4) Msun within a radius of 0.23 pc; we also estimate the bulk heliocentric\nvelocity of the cluster to be v_{cluster,odot} approximately +95 kms^{-1}.\n