Spatially extended K I λ7699 emission in the nebula of VY CMa: Kinematics and geometry

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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.

Original languageEnglish (US)
Pages (from-to)L31-L35
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - Apr 1 2004


  • Circumstellar matter
  • Stars: evolution
  • Stars: individual: VY CMa
  • Stars: mass-loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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