Caffau, E.E.CaffauBonifacio, P.P.BonifacioSpite, M.M.SpiteSpite, F.F.SpiteMonaco, L.L.MonacoSbordone, L.L.SbordoneFrançois, P.P.FrançoisGallagher, A. J.A. J.GallagherPlez, B.B.PlezZAGGIA, SimoneSimoneZAGGIALudwig, H. -G.H. -G.LudwigCayrel, R.R.CayrelKoch, A.A.KochSteffen, M.M.SteffenSalvadori, S.S.SalvadoriKlessen, R.R.KlessenGlover, S.S.GloverChristlieb, N.N.Christlieb2022-07-202022-07-2020160004-6361http://hdl.handle.net/20.500.12386/32530Aims: 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.STAMPAenArticle10.1051/0004-6361/201629776https://www.aanda.org/articles/aa/full_html/2016/11/aa29776-16/aa29776-16.html2016A&A...595L...6CFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems