A new method for an objective, χ2-based spectroscopic analysis of early-type stars - First results from its application to single and binary B- and late O-type stars

Context. A precise quantitative spectral analysis, encompassing atmospheric parameter and chemical elemental abundance determination, is time-consuming due to its iterative nature and the multi-parameter space to be explored, especially when done by the naked eye. Aims. A robust automated fitting technique that is as trustworthy as traditional methods would allow for large samples of stars to be analyzed in a consistent manner in reasonable time. Methods. We present a semi-automated quantitative spectral analysis technique for early-type stars based on the concept of chi(2) minimization. The method's main features are as follows: far less subjectivity than the naked eye, correction for inaccurate continuum normalization, consideration of the whole useful spectral range, and simultaneous sampling of the entire multi-parameter space (effective temperature, surface gravity, microturbulence, macroturbulence, projected rotational velocity, radial velocity, and elemental abundances) to find the global best solution, which is also applicable to composite spectra. Results. The method is fast, robust, and reliable as seen from formal tests and from a comparison with previous analyses. Conclusions. Consistent quantitative spectral analyses of large samples of early-type stars can be performed quickly with very high accuracy.