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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - TOPoS: III. An ultra iron-poor CEMP multiple system
AU - Caffau, E.
AU - Bonifacio, P.
AU - Spite, M.
AU - Spite, F.
AU - Monaco, L.
AU - Sbordone, L.
AU - Francois, P.
AU - Gallagher, A.
AU - Plez, B.
AU - Zaggia, S.
AU - Ludwig, H.-G.
AU - Cayrel, R.
AU - Koch, Andreas
AU - Steffen, M.
AU - Salvadori, S.
AU - Klessen, R.S.
AU - Glover, S.
AU - Christlieb, N.
PY - 2016/11
Y1 - 2016/11
N2 - Aims. One of the primary objectives of the TOPoS survey is to search for the most metal-poor stars. Our search has led to the discovery of one of the most iron-poor objects known, SDSS J092912.32+023817.0. This object is a multiple system, in which two components are clearly detected in the spectrum. Methods. We have analysed 16 high-resolution spectra obtained using the UVES spectrograph at the ESO 8.2 m VLT telescope to measure radial velocities and determine the chemical composition of the system. Results. Cross correlation of the spectra with a synthetic template yields a double-peaked cross-correlation function (CCF) for eight spectra, and in one case there is evidence for the presence of a third peak. Chemical analysis of the spectrum obtained by averaging all the spectra for which the CCF showed a single peak found that the iron abundance is [Fe/H]=–4.97. The system is also carbon enhanced with [C/Fe]=+3.91 (A(C) = 7.44). From the permitted oxygen triplet we determined an upper limit for oxygen of [O/Fe]< +3.52 such that C/O > 1.3. We are also able to provide more stringent upper limits on the Sr and Ba abundances ([Sr/Fe] < +0.70, and [Ba/Fe] < +1.46, respectively).
AB - Aims. One of the primary objectives of the TOPoS survey is to search for the most metal-poor stars. Our search has led to the discovery of one of the most iron-poor objects known, SDSS J092912.32+023817.0. This object is a multiple system, in which two components are clearly detected in the spectrum. Methods. We have analysed 16 high-resolution spectra obtained using the UVES spectrograph at the ESO 8.2 m VLT telescope to measure radial velocities and determine the chemical composition of the system. Results. Cross correlation of the spectra with a synthetic template yields a double-peaked cross-correlation function (CCF) for eight spectra, and in one case there is evidence for the presence of a third peak. Chemical analysis of the spectrum obtained by averaging all the spectra for which the CCF showed a single peak found that the iron abundance is [Fe/H]=–4.97. The system is also carbon enhanced with [C/Fe]=+3.91 (A(C) = 7.44). From the permitted oxygen triplet we determined an upper limit for oxygen of [O/Fe]< +3.52 such that C/O > 1.3. We are also able to provide more stringent upper limits on the Sr and Ba abundances ([Sr/Fe] < +0.70, and [Ba/Fe] < +1.46, respectively).
KW - stars: Population II
KW - stars: abundances
KW - stars: Population III
KW - Galaxy: abundances
KW - Galaxy: formation
KW - Galaxy: halo
U2 - 10.1051/0004-6361/201629776
DO - 10.1051/0004-6361/201629776
M3 - Journal article
VL - 595
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 1432-0746
M1 - L6
ER -