Beryllium abundances in Hg-Mn stars

The Hg-Mn stars show anomalous line strengths of many chemical elements including Be. The Be II resonance doublet has been observed at 3130, 3131 A at 6.7 A/mm in 43 Hg-Mn stars and 10 normal stars in the same temperature range with the coude spectrograph of the 2.24 m University of Hawaii telescope at Mauna Kea. Measured equivalent widths of the two lines and/or the blend of the doublet have been compared with the predictions from (1) LTE model atmospheres and (2) non-LTE line formation in non-LTE model atmospheres. Overabundances of factors of 20-20,000 relative to solar have been found for 75 percent of the Hg-Mn stars. The 25 percent with little or no Be are typically among the cooler Hg-Mn stars, but for the stars with Be excesses, there is only marginal evidence for a correlation of the size of the overabundance and temperature. It is suggested that diffusion driven by radiation pressure is responsible for the observed Be abundance anomalies.