AN OPTICAL-REGION ELEMENTAL ABUNDANCE ANALYSIS OF THE CHEMICALLY PECULIAR HGMN STAR-(CHI)-LUPI

The optical spectrum of the chemically peculiar HgMn type binary star X Lupi has been analyzed to determine atmospheric parameters and elemental abundances. Echelle spectra were obtained with the 3.9 m Anglo-Australian telescope to exploit the extreme shape-lined nature of the spectrum. This study was undertaken in support of ultraviolet analyses currently underway that utilize echelle spectra obtained with the Hubble Space Telescope. For the B9.5 V primary star we obtain T-eff = 10650 K, log g = 3.9, and xi = 0 km s(-1), while for the A2 V secondary, T-eff = 9200 K, log g = 4.0, and xi = 2 km s(-1). Most of the elemental abundances are typical of HgMn stars with similar T-eff, showing an overall iron-peak elemental abundance distribution that is basically solar in nature with enhancement of the light elements Si P, and S, as well as all detected elements heavier than the iron group. Abundances for several elements have been determined for the first time in this star, including several of the rare-earths. The secondary star spectrum shows Am star characteristics. We also discuss the relative merits of the equivalent width and synthetic spectrum techniques in determining the elemental abundances, concluding that the synthetic spectrum technique is necessary for obtaining abundances with the utmost accuracy.