MONOS. I. Spectral classifications

We also use lucky images obtained with AstraLux. We present homogeneous spectral classifications for 92 O-type spectroscopic multiple systems and ten optical companions, many of them original.We discuss the visual multiplicity of each system with the support of AstraLux images and additional sources. For eleven O-type objects and for six B-type objects we present their first GOSSS spectral classifications.

For two known eclipsing binaries we detect double absorption lines (SB2) or a single moving line (SB1) for the first time, to which we add a third system already reported by us recently. For two previous SB1 systems we detect their SB2 nature for the first time and give their first separate spectral classifications, something we also do for a third object just recently identified as a SB2. We also detect nine new astrometric companions and provide updated information on several others.

We emphasize the results for two stars: for {sigma} Ori AaAbB we provide spectral classifications for the three components with a single observation for the first time thanks to a lucky spectroscopy observation obtained close to the Aa,Ab periastron and for {theta}^1^ Ori CaCb we add it to the class of Galactic Of?p stars, raising the number of its members to six. Our sample of O-type spectroscopic binaries contains more triple- or higher-order systems than double systems.