Stelios Tsangarides

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We report on a programme to monitor the radial velocities of a sample of candidate and confirmed carbon-enhanced, metal-poor (CEMP) stars. We observed 45 targets using the Echelle Spectrographs of three 4-m class telescopes. Radial velocities for these objects were calculated by cross-correlation of their spectra with the spectrum of HD 140283, and have(More)
We discuss radial velocities for a sample of carbon-enhanced, s-process–rich, very metal-poor (CEMP-s) stars, analyzed with high-resolution spectroscopy obtained over multiple epochs. We find that 68% of the stars in the sample show evidence of radial velocity variations. The expected detection fraction for these stars, adopting the measured binary fraction(More)
An abundance analysis for the carbon-enhanced, extremely iron-poor ([Fe/H]∼ −3.5) star CS 29498–043 has been obtained using new high-resolution, high signalto-noise spectra from the Subaru Telescope. The [O I] forbidden line at 6300 Å and the O I triplet feature at 7771-7776 Å are both clearly detected. The overabundance of oxygen is significant ([O/Fe]>(More)
We present results of an analysis of high-resolution spectra (R ∼ 50 000), obtained with the Subaru Telescope High Dispersion Spectrograph, of two CarbonEnhanced Metal-Poor (CEMP) stars selected from the Hamburg/ESO prism survey, HE 1305+0007 and HE 1152−0355, and of the classical CH star HD 5223. All of these stars have relatively low effective(More)
We have investigated the abundances of heavy neutron-capture elements, including osmium (Os) and iridium (Ir), in the two carbon-enhanced metal-poor (CEMP) subgiants CS 31062-050 and LP 625-44. CS 31062-050 is known to be a so-called CEMP-r/s star, which exhibits large excesses of s-process elements such as barium (Ba) and lead (Pb), as well as a(More)
An abundance analysis for the carbon-enhanced, extremely iron-poor ([Fe/H]∼ −3.5) star CS 29498–043 has been obtained using new high-resolution, high signalto-noise spectra from the Subaru Telescope. The [O I] forbidden line at 6300 Å and the O I triplet feature at 7771-7776 Å are both clearly detected. The overabundance of oxygen is significant ([O/Fe]>(More)
We describe the discovery of HE 1327−2326, a dwarf or subgiant with [Fe/H] = −5.4. The star was found in a sample of bright metal-poor stars selected from the Hamburg/ESO survey. Its abundance pattern is characterized by very high C and N abundances. The detection of Sr which is overabundant by a factor of 10 as compared to iron and the Sun, suggests that(More)
An abundance analysis for the carbon-enhanced, extremely iron-poor (1⁄2Fe=H 3:5) star CS 29498-043 has been obtained using new high-resolution, high signal-to-noise ratio spectra from the Subaru Telescope. The [O i] forbidden line at 6300 8 and the O i triplet feature at 7771–7776 8 are both clearly detected. The overabundance of oxygen is significant(More)
We discuss radial velocities for a sample of carbon-enhanced, s-process rich, very metal-poor stars (CEMP-s hereafter), analyzed with high-resolution spectroscopy obtained over multiple epochs. We find that ∼68% of the stars in the sample show evidence of radial velocity variations. The expected detection fraction for these stars, adopting the measured(More)
The chemical compositions of 26 metal-poor stars that exhibit strong CH and/or C2 molecular bands are determined based on high-resolution spectroscopy. We define carbon-enhanced stars taking account of the carbon abundance ratio ([C/Fe]) and the evolutionary status, which is a slight modification over previous definitions. Twenty two stars in our sample(More)