A spectroscopic investigation of the young open cluster IC 1805

We present the main results of a spectroscopic campaign devoted to the O-type stars in the young open cluster IC 1805. This study aims at the investigation of the multiplicity and the line profile variability of its brightest massive members. We present new results concerning the line profile variability of He II 4686 and H-beta for HD 15570 and HD 15629. For these two stars, our radial velocity analysis does not reveal any variations compatible with a binary motion. We also significantly improve the orbital parameters of the long period binary HD 15558. For this latter system, we present for the first time evidence for the detection of the secondary, leading to spectral types of O5.5 and O7 respectively for the two components