Origin of the heavy elements in HD 140283: measurement of europium abundance

Context. HD140283 is a nearby (V = 7:7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have\ud been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances\ud from weak lines.\ud Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the\ud s-process, as recently claimed in the literature.\ud Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code\ud Turbospectrum, we measured the europium lines at 4129 Å and 4205 Å, taking into account the hyperfine structure of the transitions.\ud The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving\ud power of 81 000 and a S/N ratio of 800 at 4100 Å.\ud Results. We were able to determine the abundance A(Eu) = \u100000�����2:35 0:07 dex, compatible with the value predicted for the europium\ud from the r-process. The abundance ratio [Eu/Ba] = +0:58 0:15 dex agrees with the trend observed in metal-poor stars and is also\ud compatible with a strong r-process contribution to the origin of the neutron-capture elements in HD140283.CAPESCNPqFAPES