A recent unambiguous detection of X-ray rotational modulation of the supersaturated star VXR45 ( P = 0.223 days ) has shown that its corona has discrete dark and bright X-ray regions .
We suggest that due to the rapid rotation , the X-ray emitting corona has been centrifugally stripped away , creating open field regions that are dark in X-rays .
This leads naturally both to a significant rotational modulation in X-rays but also to the lower X-ray luminosity of supersaturated stars compared to those rotating more slowly .
To demonstrate the effect , we take as an example a more slowly rotating star for which surface magnetograms are available .
We extrapolate the potential coronal magnetic field based on these magnetograms and determine for a hydrostatic , isothermal atmosphere the structure of the density and of the optically-thin X-ray emission .
We show that if the rotation rate of this star were increased , the magnitude of the X-ray luminosity would decrease while its rotational modulation would increase in a way that is consistent with the recent observations of VXR45 .