Volume 491, Number 1, November III 2008Diagnostics of interstellar hydrogen in the heliosphere
|Page(s)||229 - 238|
|Section||Interstellar and circumstellar matter|
|Published online||01 October 2008|
The Antares emission nebula and mass loss of Scorpii A*
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: firstname.lastname@example.org
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 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.
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 α Sco A.
Results. We found that the Antares nebula shows, in addition to numerous [Fe ii] lines, the Balmer line recombination spectrum Hα, H up to H10, and [N ii] 6583/6548 Å, Hα 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 Hα velocities, the H ii region is found to be located ~215 AU behind the plane of the sky of α Sco A. From the Hα/[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 α 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
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