The Abundance of Zinc in Hg-Mn Stars

Abstract

The resonance line of singly ionized zinc (Zn II) at 2062.00 A is quantitatively analyzed, and the abundances of Zn in atmospheres of early-type stars have been determined for the first time. The line is analyzed in IUE spectra of six reference (normal) stars between spectral types B5 and A0 and of 23 Hg-Mn stars. The abundances of Zn in the reference stars coincide with the solar value within + or - 0.5 dex. Zn is overabundant in five Hg-Mn stars, while it is underabundant by at least 1.0 dex in 12 of them. The Hg-Mn stars Phi Her and Mu Lep show the strongest and the weakest Zn II lines, respectively, and the abundance of Zn in Phi Her is at least 100,000 times higher than that in Mu Lep. No clear dependence of the Zn abundance on the effective temperature is found. There also is no clear correlation between the degree of abundance anomaly of Zn and those of the two neighboring elements Cu and Ga. A definite nonsolar abundance pattern, excesses of both Cu and Ga over Zn, is found for six Hg-Mn stars.