A&A 491, 229-238 (2008)
The Antares emission nebula and mass loss of Scorpii AD. Reimers, H.-J. Hagen, R. Baade, and K. Braun
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
Received 16 April 2008 / Accepted 25 August 2008
Aims. The Antares nebula is a peculiar emission nebula seen in numerous [ ] lines and in radio free-free emission, probably associated with the H II region caused by Sco B in the wind of 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 Sco A.
Methods. The Antares nebula was mapped with long-slit (10) and high-resolution (R = 80 000) spectra using UVES at the VLT. The resulting 2-D images were used to reconstruct a 3-D picture of the H II region and its absolute location in space relative to Sco A.
Results. We found that the Antares nebula shows, in addition to numerous [Fe II] lines, the Balmer line recombination spectrum H, H up to H10, and [N II] 6583/6548 Å, H and [N II] with the same extent as seen in cm radio free-free emission. Combining velocity information from optical and GHRS/HST spectra with H velocities, the H II region is found to be located ~215 AU behind the plane of the sky of Sco A. From the H/[N II] intensity ratio and the non-visibility of the [O II] 3726/3729 Å lines we estimate a low mean electron temperature of = 4900 K and an N abundance enhanced by a factor of ~3 due to the CNO cycle in Sco A. The shape and size of the H II region yield a mean mass-loss rate of (1.05 0.3) 10-6 yr-1. The [Fe II] lines originate predominantly at the edges (rear and front) of the H II region. UV continuum pumping as well as collisional excitation seem to be responsible for the observed iron lines.
Key words: binaries: visual -- circumstellar matter -- stars: mass-loss -- stars: late-type
© ESO 2008