2013A&A...558A..36C

The aim of this study is a detailed abundance analysis of the newly discovered r-rich star HE 1405-0822, which has [Fe/H]=-2.40. This star shows enhancements of both r- and s-elements, [Ba/Fe]=+1.95 and [Eu/Fe]=1.54, for which reason it is called r+s star. Stellar parameters and element abundances were determined by analyzing high-quality VLT/UVES spectra. We used FeI line excitation equilibria to derive the effective temperature. The surface gravity was calculated from the FeI/FeII and TiI/TiII equilibria. We determined accurate abundances for 39 elements, including 19 neutron-capture elements. HE 1405-0822 is a red giant. Its strong enhancements of C, N, and s-elements are the consequence of enrichment by a former AGB companion with an initial mass of less than 3M_☉. The heavy n-capture element abundances (including Eu, Yb, and Hf) seen in HE 1405-0822 do not agree with the r-process pattern seen in strongly r-process-enhanced stars. We discuss possible enrichment scenarios for this star. The enhanced α elements can be explained as the result of enrichment by supernovae of type II. Na and Mg may have partly been synthesized in a former AGB companion, when the primary ²²Ne acted as a neutron poison in the ¹³C-pocket.