The Discovery of Hot Stars near the Galactic Center Thermal Radio Filaments

We report the discovery of a highly unusual cluster of stars at GO.121+0.017 near the Arched (thermal) Filaments, ∼10' northeast of the Galactic center. H (1.65 μm) and K' (2.1 μm) 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 Brγ (2.166 μm) emission: 12 of these stars also have He I (2.112/3 μm) emission, and two show fainter He 11(2.189 μm) 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 ∼14% of all known Galactic WN stars.

Observations of emission-line stars near GO. 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.