Stellar compositions from narrow-band photometry

Using narrow-band spectrophotometric indices interpreted with synthetic spectra computed from model atmospheres, barium abundances have been measured for 200 stars with uncertainties of about 0.3 in [Ba/H]. The results suggest that there is a continuous distribution of [Ba/Fe] from the Ba II stars to barium poor stars and that the latter, at least, reflect a variation of [Ba/Fe] in the interstellar medium which may be correlated with [Fe/H]. Several possible new Ba II stars have been found and the frequency of Ba II stars amongst G and K giants appears to lie between 1 and 4 per cent. Only one of the candidate Ba II stars appears to have strong CN and CH absorption and the candidates cover a wide range in luminosity. Masses between 0.5 ℳ⊙ and 50 ℳ⊙ were derived for Ba II stars which also have spectroscopic gravities or [Pe] derived in other analyses. Most Ba II stars appear to have young disk kinematics. It is confirmed that the peculiar colours of many Ba II stars are caused by excess blanketing due to CN, CH and C2.