Based on observations collected at the European Southern Observatory, Chile (ESO N $^{\circ}$ 074.B-0455(A)) and at the Centro Astronómico Hispano Alemán at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía.

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Table 1 and Figs. 16-19 are only available in electronic form at http://www.aanda.org

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... observations

We expect our approach to be valid at slightly hotter temperatures, at least in main sequence stars where the stellar wind does not influence the photospheric layers strongly.

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... IV

In particular on the oscillator strengths of the Fe IV transitions involved. A reduction of the gf-values may alleviate the discrepancy between the He I singlet and triplet line strengths, seen, for example, in the OSTAR2002 grid.

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...2006)

As a further test we have calculated synthetic spectra for the (35 000, 4.5) and (32 500, 3.75) models on the basis of unified, line-blanketed non-LTE model atmospheres (FASTWIND, Puls et al. 2005). Excellent agreement with our ADS results is found for both the He I singlet and triplet lines. Note that FASTWIND also uses an approximate treatment of line blocking.

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... spectra

Our own tests indicate that both the ADS calculations and FASTWIND provide high-quality fits to observation of the He I singlet and triplet spectra in the parameter space of interest here.

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