Heavy-element abundances in the classical barium star HR 774

Abstract

Low-noise high-resolution Digicon and Reticon spectra of HR 774 are analyzed to determine abundances for all accessible heavy elements in the visual and near-infrared. The authors find evidence of departures from LTE as large as 0.5 dex affecting the low-excitation neutral lines of heavy elements in HR 774 and the standard star (β Gem). These severe effects cancel in a comparison of HR 774 with β Gem. Abundances of 19 heavy elements (Z ≥ 37) are determined and used to derive s-process overabundances. The predicted s-process abundances fit the derived s-process abundances remarkably well. The pattern of s-process abundances is consistent with the <SUP>13</SUP>C(α, n)<SUP>16</SUP>O reaction as the neutron source and excludes the <SUP>22</SUP>Ne(α, n)<SUP>25</SUP>Mg reaction.