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Search for carbon enhanced metal-poor stars

Grant number: 07/04356-3
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): October 01, 2007
Effective date (End): August 31, 2010
Field of knowledge:Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
Principal researcher:Silvia Cristina Fernandes Rossi
Grantee:Vinicius Moris Placco
Home Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

It has been recognized that a large fraction, in excess of 20%, of stars with metallicities [Fe/H]<-2.0, exhibit large overabundances of carbon, [C/Fe]>+1.0. This fraction rises to 30% for [Fe/H]<-3.0, 40% for [Fe/H]<-3.5, and100% for [Fe/H]<-4.0. The vast majority of such stars were identified from objective-prism surveys, such as the HK survey of Beers and colleagues, and the Hamburg/ESO Survey (HES) of Christlieb and colleagues, based on weak lines of Ca II K.We propose to use the recently compiled set of line index and color information for over 1.5 million digitized spectra from the HES to assemble a list of star with unusually strong CH G bands, and obtain follow-up medium-resolution spectrawith the SOAR 4.1m telescope of a subsample of these candidates, in order to demonstrate the efficacy of searching for additional low-metallicity stars based on the expectation that many will also be strongly carbon enhanced. A list of HES stars with strong lines of carbon has been previously assembled by Christlieb et al. (2001). Spectra for most of these objects have been obtained over the past few years. Inspection of these data indicate that at least 50% of these targets are consistent with identification as Carbon-Enhanced Metal-Poor (CEMP) stars, while the others are roughly solar-abundance carbon-rich stars. However, this previous list was put together based on the SUM of molecular carbon lines, such as CN, C2, and CH, which overemphasizes cooler stars in the sample. CEMP tars with effective temperatures higher than about 5500K often only exhibit an unusual strength in just a single feature, the CH G band at 4300 A, and hence could have been missed in the previous assembly.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
PLACCO, VINICIUS M.; KENNEDY, CATHERINE R.; BEERS, TIMOTHY C.; CHRISTLIEB, NORBERT; ROSSI, SILVIA; SIVARANI, THIRUPATHI; LEE, YOUNG SUN; REIMERS, DIETER; WISOTZKI, LUTZ. SEARCHES FOR METAL-POOR STARS FROM THE HAMBURG/ESO SURVEY USING THE CH G BAND. ASTRONOMICAL JOURNAL, v. 142, n. 6 DEC 2011. Web of Science Citations: 27.
PLACCO, VINICIUS M.; KENNEDY, CATHERINE R.; ROSSI, SILVIA; BEERS, TIMOTHY C.; LEE, YOUNG SUN; CHRISTLIEB, NORBERT; SIVARANI, THIRUPATHI; REIMERS, DIETER; WISOTZKI, LUTZ. A SEARCH FOR UNRECOGNIZED CARBON-ENHANCED METAL-POOR STARS IN THE GALAXY. ASTRONOMICAL JOURNAL, v. 139, n. 3, p. 1051-1065, MAR 2010. Web of Science Citations: 17.
Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
PLACCO, Vinicius Moris. Search for very metal-poor stars based on carbon over-abundance. 2010. Doctoral Thesis - Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) São Paulo.

Please report errors in scientific publications list by writing to: cdi@fapesp.br.