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Title: On the binary helium star DY Centauri: chemical composition and evolutionary state

DY Cen has shown a steady fading of its visual light by about one magnitude in the last 40 yr, suggesting a secular increase in its effective temperature. We have conducted non-local thermodynamic equilibrium (LTE) and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 yr. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of a He white dwarf with a C-O white dwarf. Thus DY Cen by chemical composition appears to also be a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.
Authors:
;  [1] ;  [2] ;  [3]
  1. Indian Institute of Astrophysics, Bangalore 560034 (India)
  2. Armagh Observatory, Collage Hill, Armagh BT61 9DG (United Kingdom)
  3. The W. J. McDonald Observatory and Department of Astronomy, University of Texas at Austin, Austin, TX 78712-1083 (United States)
Publication Date:
OSTI Identifier:
22370587
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; BINARY STARS; GRAVITATION; HELIUM; LUMINOSITY; RESOLUTION; SPECTRA; STAR EVOLUTION; STELLAR ATMOSPHERES; SURFACES; VISIBLE RADIATION; WHITE DWARF STARS