We make new Non-LTE calculations to deduce abundances of neon from visible-region échelle spectra of selected Ne i lines in 7 normal stars and 20 HgMn stars .
We find that the best strong blend-free Ne line which can be used at the lower end of the T _ { \mathrm { eff } } range is \lambda 6402 , 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 = 8.10 ) 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 \upsilon 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 is expected to undergo gravitational settling if mixing processes are sufficiently weak , and there is no strong stellar wind .
According to the theoretical predictions of Landstreet et al .
( 42 ) , the low Ne abundances place an important constraint on the intensity of such stellar winds , which must be less than 10 ^ { -14 } M _ { \sun } yr ^ { -1 } if they are non-turbulent .