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).
Astronomy and Astrophysics
- Pub Date:
- October 2016
- stars: Population II;
- stars: abundances;
- binaries: spectroscopic;
- Galaxy: abundances;
- Galaxy: formation;
- Galaxy: halo;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- Accepted for publication in A&