SIMBAD references

The chemical composition of the open cluster NGC 6611 and the Sharpless regions S 285 and S 289 have been analysed, and stellar parameters (effective temperature, gravity, microturbulence) and chemical abundances of 4 unevolved B-stars in NGC 6611, 2 B-stars in S 285, and 1 B-star in S 289 are given. Line blanketed LTE model atmospheres and NLTE line formation calculations were used for the abundance determination of C, N, O, Mg, Al, and Si; LTE line formation calculations were used for the abundance determination of Ne, S, and Fe. In agreement with results obtained from B-type stars in the solar neighbourhood and the young open cluster NGC 6231 presented in earlier papers, all elements except neon show an average underabundance of 0.1-0.4dex with respect to the solar value. Among the cluster stars abundance differences of 0.2-0.7dex may be observed. First results for the galactic metallicity gradient show an insignificant value for most observed elements, except for neon and sulfur, which is in contrast to results of analyses of HII regions by Shaver et al. (1983).