1994A&A...285..573N

We present near-infrared spectroscopy and unified atmosphere/wind models of the brightest HeI 2.058µm emission line star (hereafter denoted AF) in the Galactic center. The near-infrared spectrum of this star exhibits broad emission lines of HeI and H, with the strongest line at 2.058µm showing shallow P-Cygni absorption, strengthening the stellar wind interpretation for the origin of the lines. None of the higher excitation lines typical of classical Wolf-Rayet stars are detected. From the atmosphere models we conclude that the star is undergoing extensive mass loss (dM/dt∼6 to 10 x 10^–5 M_☉/yr), has a luminosity of 2 to 3 10⁵L_☉, a moderate end velocity (V_∞ ∼ 700 km/s) and a strongly enhanced helium abundance (N_He/N_H>.5). The AF star has an effective temperature of about 20,000K and produces ≤10⁴⁸ Lyman continuum photons per second and < 10³⁸ helium continuum photons. These parameters are similar to those of evolved blue supergiants of type Ofpe/WN9 found in the Magellanic Clouds. Extrapolating from the AF star it is likely that the emission line stars so far detected (∼ 15) contribute a large fraction of the total luminosity (∼10⁷L_☉), and a significant fraction of the Lyman continuum luminosity (∼10⁶L_☉) of the central parsec. However, the Hei stars make no contribution to the He ionizing photons. Less evolved, hotter O and/or Wolf-Rayet stars may provide the Hei ionizing flux, and also contribute to the Lyman flux.