Spectroscopy of the Ca II Line in Metal-Poor Field Red Giants. II. Northern Hemisphere Observations

Details Spectroscopy of the Ca II Line in Metal-Poor Field Red Giants. II. Northern Hemisphere Observations Spectroscopy of the Ca II Line in Metal-Poor Field Red Giants. II. Northern Hemisphere Observations

Jul 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aj....110..405d&link_type=abstract

Astronomical Journal v.110, p.405

Astronomy and Astrophysics

Astronomy

26

Stars: Giant, Stars: Abundances, Stars: Chemically Peculiar

Scientific paper

Echelle spectra of the Ca II K line (λ3933.7) for a sample of 53 metal-deficient field giants, including first-ascent red giant branch stars and asymptotic giant branch stars, demonstrate that chromospheres are ubiquitous among these objects. The atmospheres of the metal-deficient giants are found to be quite dynamic; motions in the deeper regions of the chromosphere appear to be irregular, and evidence for both outflows and infall has been found. An absolute magnitude of MV≍-1.7 corresponds to a critical brightness for metal-deficient giants; as stars evolve beyond this magnitude the atmospheric structure and dynamics affecting the Hα and Ca II K profiles undergo a change. Metal-poor giants brighter than this magnitude exhibit evidence of systematic outflows. However, no circumstellar component is seen in any of the spectra of the Ca II K line acquired in this project. The winds of bright Population II red giants are inferred to be hotter than those of Population I giants. The classic Wilson-Bappu effect is found to depend on metal abundance.

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