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Title: Seven new carbon-enhanced metal-poor RR Lyrae stars

We report estimated carbon-abundance ratios, [C/Fe], for seven newly discovered carbon-enhanced metal-poor (CEMP) RR Lyrae stars. These are well-studied RRab stars that had previously been selected as CEMP candidates based on low-resolution spectra. For this pilot study, we observed eight of these CEMP RR Lyrae candidates with the Wide Field Spectrograph on the ANU 2.3 m telescope. Prior to this study, only two CEMP RR Lyrae stars had been discovered: TY Gru and SDSS J1707+58. We compare our abundances to new theoretical models of the evolution of low-mass stars in binary systems. These simulations evolve the secondary stars, post accretion from an asymptotic giant-branch (AGB) donor, all the way to the RR Lyrae stage. The abundances of CEMP RR Lyrae stars can be used as direct probes of the nature of the donor star, such as its mass, and the amount of material accreted onto the secondary. We find that the majority of the sample of CEMP RR Lyrae stars is consistent with AGB donor masses of around 1.5-2.0 M {sub ☉} and accretion masses of a few hundredths of a solar mass. Future high-resolution studies of these newly discovered CEMP RR Lyrae stars will help disentangle the effects ofmore » the proposed mixing processes that occur in such objects.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4] ; ;  [5] ;  [6]
  1. Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
  2. Sydney Institute for Astronomy, University of Sydney, Sydney, NSW 2006 (Australia)
  3. National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
  4. Gemini Observatory, Hilo, HI 96720 (United States)
  5. Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, SP 05508-900 (Brazil)
  6. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
Publication Date:
OSTI Identifier:
22356893
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ASYMPTOTIC SOLUTIONS; CARBON; COMPARATIVE EVALUATIONS; GALAXIES; MASS; METALS; RESOLUTION; SIMULATION; SPECTRA; STARS; TELESCOPES