A Search for Unrecognized Carbon-Enhanced Metal-Poor Stars

Abstract

We have developed a new procedure to search for Carbon-Enhanced Metal-Poor (CEMP) stars from the Hamburg/ESO (HES) prism-survey plates. This method uses an extended line index for the CH G-band, which we demonstrate to have superior behavior when compared to the narrower G-band index formerly employed for these spectra. A first subsample, biased towards brighter stars (B<15.5), has been extracted from the scanned HES plates. After visual inspection (to eliminate spectra compromised by plate defects, overlapping spectra, etc., and to carry out rough spectral classifications), a list of 669 previously unidentified candidate CEMP stars was compiled. Follow-up spectroscopy for a pilot sample of 132 candidates was obtained on the SOAR 4.1m telescope. Our results show that most of the stars observed lie in the targetted metallicity range, and possess prominent carbon absorption features at 4300˚A. The success rate for the identification of new CEMP stars is ∼50% for [Fe/H]< −2.0. For stars with [Fe/H]< −2.5, the ratio increases to 100%.