Detection of intrinsic variability in the eclipsing massive main sequence O+B binary HD 165246

We present the analysis of 29.77 days of K2 space photometry of the well-detached massive 4.6 d O+B binary HD 165246 (V=7.8) obtained during Campaign 9b. This analysis reveals intrinsic variability in the residual lightcurve after subtraction of the binary model, in the frequency range [0,10] $d^{-1}$. This makes HD 165246 only the second O+B eclipsing binary with asteroseismic potential. While some of the frequencies are connected with the rotation of the primary, others are interpreted as due to oscillations with periodicities of order days. The frequency resolution of the current dataset does not allow to distinguish between frequencies due to standing coherent oscillation modes or travelling waves. Further time-resolved high-precision spectroscopy covering several binary orbits will reveal whether HD 165246 is a Rosetta stone for synergistic binary and seismic modelling of an O-type star.