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An Abundance Analysis of Fehrenbach’s Star (HD 116745) in Omega Centauri
Published online by Cambridge University Press: 12 April 2016
Abstract
HD 116745 is an eleventh magnitude early F-type giant occurring in the field of the globular cluster ω Cen. Membership in the cluster appears virtually certain since the star’s radial velocity differs insignificantly from the mean cluster velocity of +238 km s-1. HD 116745 lies nearly 4 mag. above the horizontal branch in the HR diagram and is presumably in a rapid, advanced stage of evolution. Spectrograms at 22.5 Å mm-1 and 155 Å mm-1 have been obtained by one of us (R.J.D.) at the Radcliffe Observatory in South Africa using a McGee spectracon image tube. The lower dispersion spectra have been used to measure Hy profiles and the Balmer discontinuity, and one high dispersion film has provided the basis for a differential curve-of-growth analysis with respect to the Sun in order to determine some heavy element abundances. Physical data derived for the star are Mv= –3.32, θe=0.77±0.02, logg = 1.0±0.3 and Results of the curve-of-growth analysis, in which a model atmosphere was used to determine the curve appropriate to the star, yield a logarithmic iron-to-hydrogen abundance ratio with respect to the Sun of [Fe/H]= —1.2 with a provisional estimated uncertainty of about +0.2. This result is based on 28 lines of Fe i. Ti may be marginally overabundant, with a value of [Ti/Fe] = + 0.4, based on 7 lines of Ti II. Other elements and ionization states identified are Mg I, Al I, Si I, Ca I, Sc II, VI, VII, Mn I, Sr II, Zr II (Eu II).
- Type
- Part I / General Problems of Variables in Population II Systems
- Information
- International Astronomical Union Colloquium , Volume 21: Variable Stars in Globular Clusters and in Related Systems , August 1973 , pp. 29 - 30
- Copyright
- Copyright © Reidel 1973