X-ray counterpart of the shortest activity cycle found to date

Activity cycles are commonly found among late type stars through thechromospheric CaII emission. Their coronal counterpart, however, remains elusivein most cases, despite of the clear cycle observed in the solar corona, spanningas much as 1.7 dex in Lx. The recent discovery of a CaII cycle in HR 810 of just1.6 yr, the shortest to date, offers a unique opportunity to test the existenceof an Xray counterpart of the cycle within one or at most two XMMNewtonobserving periods. The star offers also two more attractives: with an age ofonly 500 Myr and spectral type G0V it represents a young solar analog, and aplanet of 1.9 Mj orbits the star at 0.9 a.u. We intend to make 8 snapshotsduring AO10, for a total of 40 ks, to cover 60% of the cycle starting near its lowest level of activity. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]