Isotopic composition of HG and Pt in 5 slowly rotating HgMn stars

Abstract

Theoretical models addressing the origin of peculiarities in the spectra of HgMn stars have not been sufficiently constrained so far by the available abundance data. Previous studies of Hg and Pt in samples of HgMn stars often relied on spectra of rather low resolution and low S/N ratio, so that only limited information could be derived from the centroid wavelength of unresolved isotopic blends. In this paper we present the results of a study of the isotopic compositions of Hg and Pt in 5 very slowly rotating HgMn stars. This work represents an improvement over previous studies due to the availability of very high spectral resolution (R = 118 000) and to the new information on wavelengths and atomic structure of Hg II and Pt II. Each of the observed stars has Hg overabundant by more than 5 dex compared with the solar abundance. The largest overabundance of Pt (4.59 dex) was found in the star HD 193452. No star shows terrestrial isotopic proportions. The most pronounced deviation from the terrestrial composition is found in the stars HD 141556 and HD 193452, which are the coolest ones in our sample. Based on observations obtained at the European Southern Observatory, La Silla, Chile (ESO programme No.~58.D-0654)