UBVJHK synthetic photometry of Galactic O stars

Aims. The development of powerful infrared observational techniques enables the study of very extincted objects and young embedded star-forming regions. This is especially interesting in the context of massive stars that form and spend a non negligible fraction of their life still enshrouded in their parental molecular cloud. Spectrophotometric calibrations are thus necessary to constrain the physical properties of heavily extincted objects. Methods. Here, we derive UBVJHK magnitudes and bolometric corrections from a grid of atmosphere models for O stars. Bessel passbands are used. Bolometric corrections (BC) are derived as a function of T-eff and are subsequently used to derive BC-spectral type (ST) and absolute magnitudes-ST relations. Results. Infrared magnitudes and, for the first time, bolometric corrections are given for the full range of spectral types and luminosity classes. Infrared colors are essentially constant, and (H-K)(0) is 0.05 mag bluer than previously proposed. Optical calibrations are also provided and are similar to previous work, except for (B - V)(0) which is found to be at minimum - 0.28 for standard O stars, slightly higher (0.04 mag) than commonly accepted. Conclusions. We present a consistent set of photometric calibrations of optical and infrared magnitudes and bolometric corrections for Galactic O stars as a function of T-eff and spectral type based on non-LTE atmosphere models including winds and line-blanketing.