2008A&A...491..229R

The Antares nebula is a peculiar emission nebula seen in numerous [FeII] lines and in radio free-free emission, probably associated with the HII region caused by α Sco B in the wind of α Sco A. High-resolution spectra with spatial resolution were used to study the emission line spectrum, the physical nature of the nebula and to determine the mass-loss rate of the M supergiant α Sco A. The Antares nebula was mapped with long-slit (10") and high-resolution optical and GHRS/HST spectra with H_α velocities, the HII region is found to be located ∼215AU behind the plane of the sky of α Sco A. From the H_α/[NII] intensity ratio and the non-visibility of the [OII] 3726/3729Å lines we estimate a low mean electron temperature of <T>_e=4900K and an N abundance enhanced by a factor of ∼3 due to the CNO cycle in α Sco A. The shape and size of the HII region yield a mean mass-loss rate of (1.05±0.3)x10^–6M_☉/yr. The [FeII] lines originate predominantly at the edges (rear and front) of the HII region. UV continuum pumping as well as collisional excitation seem to be responsible for the observed iron lines.