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A B S T R A C TWe make new non-local thermodynamic equilibrium calculations to deduce the abundances of neon from visible-region echelle spectra of selected Ne i lines in seven normal stars and 20 HgMn stars. We find that the best strong blend-free Ne line that can be used at the lower end of the effective temperature T eff range is l6402, although several other potentially useful Ne i lines are found in the red region of the spectra of these stars. The mean neon abundance in the normal stars log A 8X10 is in excellent agreement with the standard abundance of neon (8.08). However, in HgMn stars neon is almost universally underabundant, ranging from marginal deficits of 0.1±0.3 dex to underabundances of an order of magnitude or more. In many cases, the lines are so weak that only upper limits can be established. The most extreme example found is y Her with an underabundance of at least 1.5 dex. These underabundances are qualitatively expected from radiative acceleration calculations, which show that Ne has a very small radiative acceleration in the photosphere, and that it is expected to undergo gravitational settling if the mixing processes are sufficiently weak and there is no strong stellar wind. According to theoretical predictions, the low Ne abundances place an important constraint on the intensity of such stellar winds, which must be less than 10 214 M ( yr 21 if they are non-turbulent.

A B S T R A C TWe use exact curve-of-growth analysis and spectral synthesis to deduce the abundance of Mn from high signal-to-noise ratio visible-region echelle spectra of selected Mn i and Mn ii lines in 24 HgMn stars. The results are compared with the Mn abundances derived from UV resonance lines by Smith & Dworetsky. We ®nd excellent agreement for several unblended Mn lines and con®rm the temperature dependence of the Mn abundance found by Smith & Dworetsky. The Mn ii lines at ll4206 and 4326 are much stronger than one would predict from the mean Mn abundances. The lack of agreement is greatest for stars with the strongest Mn ii lines. Using ad hoc multicomponent ®ts to the pro®les of sharp-lined stars, we show that most of the discrepancies can be explained by hyper®ne structure that desaturates the lines, with full widths of the order of 0.06±0.09 A Ê .

Elemental abundances from recent spectrum-synthesis analyses of the ultraviolet spectra of normal and HgMn-type late-B stars are examined for inter-correlations and for correlations with stellar parameters by use of standard statistical techniques. A few marginally significant correlations are apparent in the normal-star sample. In the HgMn sample, significant correlations with Teff are identified for Mn, Cu, and Ga. Strong inter-correlations are also identified in this sample for the abundances of two triads of elements (Mg-Al-Cr and Mn-Cu-Ga). Trivariate correlation analysis is used to demonstrate that these element-element inter-correlations are statistically independent of both Teff and log g. The correlated behaviour of these characteristically anomalous elements casts new light on the apparent heterogeneity of the HgMn class of peculiar stars, and may have important implications for the diffusion model which has been advocated as an explanation of the HgMn phenomenon.