A SEARCH FOR UNRECOGNIZED CARBON-ENHANCED METAL-POOR STARS IN THE GALAXY

Author(s)

Placco, Vinicius M. ^[1] ; Kennedy, Catherine R. ^{[2, 3]} ; Rossi, Silvia ^[1] ; Beers, Timothy C. ^{[2, 3]} ; Lee, Young Sun ^{[2, 3]} ; Christlieb, Norbert ^[4] ; Sivarani, Thirupathi ^[5] ; Reimers, Dieter ^[6] ; Wisotzki, Lutz ^[7]

Affiliation

^[1] Univ Sao Paulo, Dept Astron, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil

^[2] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 - USA

^[3] Michigan State Univ, JINA, E Lansing, MI 48824 - USA

^[4] Univ Heidelberg, Zentrum Astron, D-69117 Heidelberg - Germany

^[5] Indian Inst Astrophys, Bangalore 560034, Karnataka - India

^[6] Univ Hamburg, D-21029 Hamburg - Germany

^[7] Astrophys Inst Potsdam, D-14482 Potsdam - Germany

• Document type: Journal article
• Source: ASTRONOMICAL JOURNAL; v. 139, n. 3, p. 1051-1065, MAR 2010.
• Web of Science Citations: 17

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 employs an extended line index for the CH G band, which we demonstrate to have superior performance when compared to the narrower G-band index formerly employed to estimate G-band strengths for these spectra. Although CEMP stars have been found previously among candidate metal-poor stars selected from the HES, the selection on metallicity undersamples the population of intermediate-metallicity CEMP stars (-2.5 <= {[}Fe/H] <= -1.0); such stars are of importance for constraining the onset of the s-process in metal-deficient asymptotic giant branch stars (thought to be associated with the origin of carbon for roughly 80% of CEMP stars). The new candidates also include substantial numbers of warmer carbon-enhanced stars, which were missed in previous HES searches for carbon stars due to selection criteria that emphasized cooler stars. A first subsample, biased toward 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 with the Goodman spectrograph on the SOAR 4.1 m telescope. Our results show that most of the observed stars lie in the targeted metallicity range, and possess prominent carbon absorption features at 4300 angstrom. The success rate for the identification of new CEMP stars is 43% (13 out of 30) for {[}Fe/H] < -2.0. For stars with {[}Fe/H] < -2.5, the ratio increases to 80% (four out of five objects), including one star with {[}Fe/H] < -3.0. (AU)

• FAPESP's process: 07/04356-3 - Search for carbon enhanced metal-poor stars
• Grantee: Vinicius Moris Placco
• Support Opportunities: Scholarships in Brazil - Doctorate