The resonance lines of HG II in IUE spectra of chemically peculiar stars.

Abstract

High-dispersion IUE observations of the two resonance lines of Hg II, at 1650 and 1942 Å, are presented for two normal stars, ν Cap and π Cet; for the HgMn stars κ Cnc, μ Lep, 46 Dra, ι CrB, HR 4072, and χ Lup; and for the magnetic variable α²CVn. These peculiar stars have all been classified as Hg-rich on the basis of their strong 3984 Å features. The six HgMn stars all possess strong Hg II resonance lines, which confirms the reality of the Hg anomaly. The magnetic star α²CVn possesses moderately strong Hg II resonance lines. Quantitative spectrum syntheses of the 1942 Å line in these stars are described. Detailed curve-of-growth analyses of the 3984 Å feature in the HgMn stars, based on published equivalent widths, are also presented. It is shown that departures from LTE are ruled out as source of the Hg anomaly. The primordial abundance of Hg is discussed and possible explanations of the Hg anomaly are considered.