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

Abstract

view Abstract Citations (32) References (73) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopy of the Ca II Line in Metal-Poor Field Red Giants. II. Northern Hemisphere Observations Dupree, A. K. ; Smith, Graeme H. Abstract 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. Publication: The Astronomical Journal Pub Date: July 1995 DOI: 10.1086/117531 Bibcode: 1995AJ....110..405D Keywords: STARS: GIANT; STARS: ABUNDANCES; STARS: CHEMICALLY PECULIAR full text sources ADS | data products SIMBAD (32) Related Materials (1) Part 1: 1992AJ....104.2005S