Caffau, E.Bonifacio, P.Spite, M.Spite, F.Monaco, L.Sbordone, L.François, P.Gallagher, A.J.Plez, B.Zaggia, S.Ludwig, H.-G.Cayrel, R.Koch, A.Steffen, M.Salvadori, S.Klessen, R.Glover, S.Christlieb, N.2023-08-282023-08-282016-11Astronomy and Astrophysics. Volume 595. 1 November 2016. Article number L60004-6361https://repositorio.unab.cl/xmlui/handle/ria/52874Indexación: Scopus.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).enStars: Population IIStars: AbundancesBinaries: SpectroscopicGalaxy: AbundancesGalaxy: HaloArtículoAtribution 4.0 International (CC BY 4.0)10.1051/0004-6361/201629776