A survey of H-alpha line profiles among metal-deficient field red giants

Abstract

view Abstract Citations (51) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Survey of Hα Line Profiles Among Metal-Deficient Field Red Giants Smith, Graeme H. ; Dupree, A. K. Abstract Echelle spectra have been obtained of the Hα line for a sample of 52 metal-poor field red giants to infer the structure and dynamics of their atmospheres. Emission is found in the wings of the absorption line for ten of these stars. The main properties of this emission are as follows (1) Only giants brighter than MV = -1.7 are found to exhibit Hα emission above the continuum level. (2) Both the absolute strength of the Hα emision wings and the sense of the violet to red (V/R) asymmetry change from star to star. (3) The strength of the emission also varies on a timescale of months for some stars, and may even disappear. Following the precepts of Dupree, Hartmann, and Avrett, the Hα emission is considered to arise from a chromosphere, particularly from relatively high-density regions with temperatures in the range 7000 - 8500K. The V/R emission asymmetries imply the existence of differential mass motions in the line-forming region. It is further proposed that the variability of the emission strength results from fluctuations within the chromosphere, of the column density or the temperature gradient, or both, possibly as the result of pulsation. Publication: The Astronomical Journal Pub Date: May 1988 DOI: 10.1086/114751 Bibcode: 1988AJ.....95.1547S Keywords: Emission Spectra; H Alpha Line; Red Giant Stars; Stellar Atmospheres; Stellar Spectra; Astronomical Catalogs; Color-Magnitude Diagram; Stellar Luminosity; Astrophysics; STARS: ATMOSPHERES; STARS: ABUNDANCES; STARS: SPECTRAL CLASSIFICATION full text sources ADS | data products SIMBAD (42)