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The detection of pulsational frequencies in stellar photometry is required asinput for asteroseismological modelling. The second short run (SRa02) of theCoRoT mission has provided photometric data of unprecedented quality andtime-coverage for a number of O-type stars. We analyse the CoRoT datacorresponding to three hot O-type stars, describing the properties of theirlight curves and we search for pulsational frequencies, which we then compareto theoretical model predictions. We determine the amplitude spectrum of thedata, using the Lomb-Scargle and a multifrequency HMM-like technique.Frequencies are extracted by prewhitening, and their significance is evaluatedunder the assumption that the light curve is dominated by red noise. We searchfor harmonics, linear combinations and regular spacings among thesefrequencies. We use simulations with the same time sampling as the data as apowerful tool to judge the significance of our results. From the theoreticalpoint of view, we use the MAD non-adiabatic pulsation code to determine theexpected frequencies of excited modes. A substantial number of frequencies islisted, but none can be convincingly identified as being connected topulsations. The amplitude spectrum is dominated by red noise. Theoreticalmodelling shows that all three O-type stars can have excited modes but therelation between the theoretical frequencies and the observed spectrum is notobvious. The dominant red noise component in the hot O-type stars studied hereclearly points to a different origin than the pulsations seen in cooler Ostars. The physical cause of this red noise is unclear, but we speculate on thepossibility of sub-surface convection, granulation, or stellar windinhomogeneities being responsible.

Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150 and HD 46966