TOPoS. III. An ultra iron-poor multiple CEMP system

Journal
Date Issued
2016
Author(s)
Caffau, E.
•
Bonifacio, P.
•
Spite, M.
•
Spite, F.
•
Monaco, L.
•
Sbordone, L.
•
François, P.
•
Gallagher, A. J.
•
Plez, B.
•
•
Ludwig, H. -G.
•
Cayrel, R.
•
Koch, A.
•
Steffen, M.
•
Salvadori, S.
•
Klessen, R.
•
Glover, S.
•
Christlieb, N.
DOI
Abstract
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). Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 094.D-0488 and 096.D-0616.
Volume
595
Start page
L6
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2016A&A...595L...6C
Rights
open.access
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