Quantitative near infra-red spectroscopy of massive stars

Interest in near infra-red spectroscopy of massive stars has increased dramatically over the last decades, as it offers the possibility to analyze stars embedded in dusty star forming regions and near the Galactic center. We present an analysis of both high resolution optical and, separately, high resolution VLT/CRIRES near-IR spectra in the J, H, K and L-band of nearby dwarf O-type stars. Applying a genetic fitting algorithm approach using state-of-the-art FASTWIND non-LTE atmospheres, we present a comparison of the stellar and wind properties as derived from these two spectral regimes. In this approach we retrieve the effective temperature to within a sub-type and the surface gravity to within 0.2 dex, but find a discrepancy in the mass-loss rates of 0.2 up to 1.0 dex. We find that He II 1012 nm and Brackett-α lines do not yield consistent mass-loss estimates, the former producing much lower values than Hα, while Brackett-α and Hα are consistent.