The discovery of hot stars near the Galactic center thermal radio filaments

We report the discovery of a highly unusual cluster of stars at G0.121+0.017 near the Arched (thermal) Filaments, similar to 10' northeast of the Galactic center. H (1.65 mu m) and K' (2.1 mu m) images are used to estimate a distance to the cluster consistent with a Galactic center location. K'-band spectroscopy reveals that the cluster contains 13 stars with Br gamma (2.166 mu m) emission: 12 of these stars also have He I (2.112/3 mu m) emission, and two show fainter He II (2.189 mu m) emission. Based on a spectral comparison with optically classified stars, we suggest the new emission stars are late WN stars. If the classification is correct, the cluster contains similar to 14% of all known Galactic WN stars. Observations of emission-line stars near G0.15-0.05, the ''Pistol,'' are also presented. There are four stars near the Pistol which contain emission lines. Three of these stars differ spectroscopically from the stars in the new cluster; one has a spectrum that is similar to the new cluster stars. Together with the cluster stars, these newly discovered hot young stars provide evidence for recent star formation and the stellar ionization of the thermal radio emission regions in the vicinity of the Galactic center.