NOAO >   Observing Info >   Approved Programs >   2009A-0249

Small NOAO Logo

Proposal Information for 2009A-0249


PI: Timothy Beers, Michigan State University, beers@pa.msu.edu
Address: Dept. of Physics & Astronomy, Michigan State University, E. Lansing, MI 48824, USA

CoI: Silvia Rossi, IAG, University of Sao Paolo, Brazil
CoI: Norbert Christlieb, University of Heidelberg, Germany
CoI: Simon Schuler, CTIO
CoI: Vinicius Placco, IAG, University of Sao Paolo, Brazil
CoI: Catherine Kennedy, Michigan State University
CoI: Thirupathi Sivarani, University of Florida

Title: A Survey for Unrecognized Carbon-Enhanced Metal-Poor Stars in the Galactic Halo

Abstract: Carbon-Enhanced-Metal-Poor (CEMP) stars are of great astrophysical interest for a host of reasons. Although the majority (80%) of such stars are known to be associated with mass-transfer events from a companion star that has evolved to the AGB stage (the CEMP-s stars), 20% of these stars do \it not exhibit s-process elements (the CEMP-no stars), and hence may be associated with zero-metallicity, massive, rapidly rotating progenitors that formed in the early Universe. Indeed, recent observations have shown that the frequency of CEMP stars increases greatly with declining [Fe/H] (some 20% of stars with [Fe/H] < -2.5 are CEMP stars, 40% below [Fe/H]=-3.5, and 100% below [Fe/H]=-4.5). Previous CEMP stars have been discovered by targeting low-metallicity candidates, based on their weak CaII K lines in objective-prism surveys, biasing away from CEMP stars with [Fe/H] > - 2.5, or by targeting stars that exhibit strong carbon signatures based on the sum of carbon line strengths in their prism spectra, biasing toward very cool stars. As a result, these targeting schemes have likely MISSED large numbers of CEMP stars, for several reasons. We propose a new selection scheme for their identification from the Hamburg/ESO prism survey, based on the strength of an extended CH G-band index.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2009A-0249

noaoprop-help@noao.edu

Small NOAO Logo