G. Catanzaro, L. A. Balona
We analyze a high-resolution spectrum of the A3m star HD27411. We compare
abundances derived from ATLAS9 model atmospheres with those using the more
computationally-intensive ATLAS12 code. We found very little differences in the
abundances, suggesting that ATLAS9 can be used for moderate chemical
peculiarity. Our abundances agree well with the predictions of diffusion
theory, though for some elements it was necessary to calculate line profiles in
non-thermodynamic equilibrium to obtain agreement. We investigate the effective
temperatures and luminosities of Am/Fm stars using synthetic Stromgren indices
derived from calculated spectra with the atmospheric abundances of HD27411. We
find that the effective temperatures of Am/Fm stars derived from Stromgren
photometry are reliable, but the luminosities are probably too low. Caution is
required when deriving the reddening of these stars owing to line blanketing
effects. A comparison of the relative proportions of pulsating and
non-pulsating Am stars with delta Scuti stars shows quite clearly that there is
no significant decrease of helium in the driving zone, contrary to current
models of diffusion.
View original:
http://arxiv.org/abs/1112.3147
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