Journal Article

The outer wind of γ Velorum

P. F. Roche, M. D. Colling and M. J. Barlow

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 427, issue 1, pages 581-588
Published in print November 2012 | ISSN: 0035-8711
Published online November 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.22005.x
The outer wind of γ Velorum

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Fine-structure mid-infrared emission lines with critical densities in the regime 104ncrit ≤ 106 cm−3 can be employed to probe the outflow from Wolf–Rayet (WR) stars at radii of ∼1015 cm. Narrow-band mid-infrared imaging and spectroscopy of the nearest WR star to the Sun, γ Velorum is analysed for spatially resolved forbidden line emission in the WR outer wind. The [S iv] 10.52-μm and [Ne ii] 12.81-μm emission regions are found to be spatially extended, compared to unresolved continuum and He and C recombination line emission. The [S iv] and [Ne ii] emission line distributions have a high degree of azimuthal symmetry, indicating a spherically symmetric outflow. A model wind with a modest degree of clumping (clumping factor f ∼ 10) provides a better match to the observations than an unclumped model. The overall line intensity distributions are consistent with a freely expanding, spherically symmetric 1/r2 outflow with constant ionization fraction and modestly clumped density structure.

Keywords: circumstellar matter; stars: abundances; stars: individual: γ Velorum; stars: winds, outflows; stars: Wolf–Rayet; infrared: stars

Journal Article.  5304 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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