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We present high-precision photometric light curves of five O-type starsobserved with the refurbished {\it Kepler\/} satellite during its Campaign 0.For one of the stars, we also assembled high-resolution ground-basedspectroscopy with the {\sc hermes} spectrograph attached to the 1.2-m Mercatortelescope. The stars EPIC202060097 (O9.5V) and EPIC202060098 (O7V) exhibitmonoperiodic variability due to rotational modulation with an amplitude of 5.6mmag and 9.3 mmag and a rotation period of 2.63 d and 5.03 d, respectively.EPIC202060091 (O9V) and EPIC202060093 (O9V:pe) reveal variability at lowfrequency but the cause is unclear. EPIC202060092 (O9V:p) is discovered to be aspectroscopic binary with at least one multiperiodic $\beta\,$Cep-type pulsatorwhose detected mode frequencies occur in the range $[0.11,6.99]$ d$^{-1}$ andhave amplitudes between 0.8 and 2.0 mmag. Its pulsation spectrum is shown to befully compatible with the ones predicted by core-hydrogen burning O-starmodels. Despite the short duration of some 33\,d and the limited data qualitywith a precision near 100 $\mu$mag of these first K2 data, the diversity ofpossible causes for O-star variability already revealed from campaigns ofsimilar duration by the MOST and CoRoT satellites is confirmed with {\itKepler}. We provide an overview of O-star space photometry and give argumentswhy future K2 monitoring during Campaigns 11 and 13 at short cadence,accompanied by time-resolved high-precision high-resolution spectroscopy opensup the possibility of in-depth O-star seismology.

Kepler's first view of O-star variability: K2 data of five O stars in Campaign 0 as a proof-of-concept for O-star asteroseismology