Elemental abundances and classification of CEMP stars
arXiv:1210.5009 · doi:10.1051/0004-6361/201015615
Abstract
We present a detailed study of Carbon-Enhanced Metal-Poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2m William Herschel Telescope (WHT) in 2001 and 2002, using the Utrecht Echelle Spectrograph (UES), at a resolving power R ~52000 and S/N ~ 40, covering the wavelength range lambda-lambda 3700-5700 A. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750 C to 7100 K, log g from 1.5 to 4.3, and metallicities -3.0 <= [Fe/H] <= -1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production.
Accepted to be published at A&A. 7 figures; 16 tables; 37 pages
References in corpus (21)
- Nucleosynthetic signatures of the first stars
- New Grids of ATLAS9 Model Atmospheres
- Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
- An extremely primitive halo star
- Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production
- HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
- The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
- The stellar content of the Hamburg/ESO survey. IV. Selection of candidate metal-poor stars
- HE 1327-2326, an unevolved star with [Fe/H]<-5.0. II. New 3D-1D corrected abundances from a VLT/UVES spectrum
- The Hamburg/ESO R-process Enhanced Star survey (HERES) III. HE 0338-3945 and the formation of the r+s stars
- New Extremely Metal-Poor Stars in the Galactic Halo
- Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
- Carbon Stars in the Hamburg/ESO Survey: Abundances
- First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor stars
- New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34 : binarity and neutron-capture elements
- CS22964-161: A Double-Lined Carbon- and s-Process-Enhanced Metal-Poor Binary Star
- A high-resolution spectral analysis of three carbon-enhanced metal-poor stars
- Chemical Abundance Analysis of the Extremely Metal-Poor Star HE 1300+0157
- The Hobby-Eberly Telescope "Chemical Abundances of Stars in the Halo" (CASH) Project. I. The Lithium-, s-, and r-Enhanced Metal-Poor Giant HKII 17435-00532
- Analysis of 26 Barium Stars II. Contributions of s-, r- and p-processes in the production of heavy elements
- Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study