Average spectrum of HD 140283 (370-1040nm)

Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. The detection of europium proves that the neutron-capture elements in this star are originate in the r-process, and not in the s-process, as recently claimed in the literature.

Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines 4129{AA} and 4205{AA}, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81000 and a S/N ratio of 800 at 4100{AA}.