The Beta Cephei star HD 180642: Full integration of CoRoT and ground data for mode identification

The B1.5 II-III star HD 180642 is the only known Beta Cephei star in CoRoT’s core programme. To complement the space data of this target, both ground-based photometric and spectroscopic data were collected, to which we added several archival observations. In this talk, we describe our results from a full integration of CoRoT and intensive ground-based observations. The star is a non-linear dominant radial mode pulsator for which low-amplitude modes are detected for the fi rst time. A few of the latter are observed in our ground-based datasets so that a mode identifi cation for them is possible. To this end state-of-the-art techniques are adapted to be applied to a star with a highly non-linear behaviour of the radial mode. Additionally, a careful interpretation of the CoRoT lightcurve helps to identify the wavenumbers. Besides this outcome, the Van Hoof effect for the dominant mode is investigated and the stellar parameters and chemical abundances are determined. All this information is to be used as additional constraints to the CoRoT pulsation frequencies, for asteroseismic modelling of this Beta Cephei star. Additional abstracts cover the lightcurve modelling of this pulsator (Degroote et al.) as well as seismic modelling (Thoul et al.).