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

Abstract

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]
  1. Indian Institute of Astrophysics, Bangalore 560034 (India)
  2. Armagh Observatory, Collage Hill, Armagh BT61 9DG (United Kingdom)
Publication Date:
OSTI Identifier:
22370587
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 793; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
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

Citation Formats

Pandey, Gajendra, Rao, N. Kameswara, Jeffery, C. Simon, and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: nkrao@iiap.res.in, E-mail: csj@arm.ac.uk, E-mail: dll@astro.as.utexas.edu. On the binary helium star DY Centauri: chemical composition and evolutionary state. United States: N. p., 2014. Web. doi:10.1088/0004-637X/793/2/76.
Pandey, Gajendra, Rao, N. Kameswara, Jeffery, C. Simon, & Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: nkrao@iiap.res.in, E-mail: csj@arm.ac.uk, E-mail: dll@astro.as.utexas.edu. On the binary helium star DY Centauri: chemical composition and evolutionary state. United States. https://doi.org/10.1088/0004-637X/793/2/76
Pandey, Gajendra, Rao, N. Kameswara, Jeffery, C. Simon, and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: nkrao@iiap.res.in, E-mail: csj@arm.ac.uk, E-mail: dll@astro.as.utexas.edu. 2014. "On the binary helium star DY Centauri: chemical composition and evolutionary state". United States. https://doi.org/10.1088/0004-637X/793/2/76.
@article{osti_22370587,
title = {On the binary helium star DY Centauri: chemical composition and evolutionary state},
author = {Pandey, Gajendra and Rao, N. Kameswara and Jeffery, C. Simon and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: nkrao@iiap.res.in, E-mail: csj@arm.ac.uk, E-mail: dll@astro.as.utexas.edu},
abstractNote = {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.},
doi = {10.1088/0004-637X/793/2/76},
url = {https://www.osti.gov/biblio/22370587}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 793,
place = {United States},
year = {Wed Oct 01 00:00:00 EDT 2014},
month = {Wed Oct 01 00:00:00 EDT 2014}
}