Open AccessSpatially extended K i λ7699 emission in the nebula of VY CMa: kinematics and geometry
Author(s) -
Smith Nathan
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07718.x
Subject(s) - physics , kinematics , nebula , geometry , astrophysics , astronomy , planetary nebula , classical mechanics , stars , mathematics
Long‐slit echelle spectra reveal bright extended emission from the K i λ7699 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 the circumstellar environment of VY CMa. Dramatic velocity structure is seen in the long‐slit spectra, and most lines of sight through the nebula 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 −1 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 stellar surface.