Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-01-02
Mon.Not.Roy.Astron.Soc. 349 (2004) L31
Astronomy and Astrophysics
Astrophysics
5 pages, 3 figures. Accepted MNRAS. Updated version with minor changes
Scientific paper
10.1111/j.1365-2966.2004.07718.x
Long-slit echelle spectra reveal bright extended emission from the K I lambda7699 resonance line in the reflection nebula surrounding the extreme red supergiant VY Canis Majoris. The central star has long been known for its unusually-bright K I emission lines, but this is the first report of intrinsic emission from K I in the nebula. The extended emission is not just a reflected spectrum of the star, but is due to resonant scattering by K atoms in the outer nebula itself, and is therefore a valuable probe of the kinematics and geometry of VY CMa's circumstellar environment. Dramatic velocity structure is seen in the long-slit spectra, and most lines of sight intersect multiple distinct velocity components. A faint ``halo'' at large distances from the star does appear to show a reflected spectrum, however, and suggests a systemic velocity of +40 km/s with respect to the Sun. The most striking feature is blueshifted emission from the filled interior of a large shell seen in images; the kinematic structure is reminiscent of a Hubble flow, and provides strong evidence for asymmetric and episodic mass loss due to localized eruptions on the star's surface.
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