tau Boo.s magnetic polarity switch in X-rays - continued monitoring

tau Boo is the first star other than the Sun which has been observed to have aglobal magnetic field with switching polarity. In contrast to the Sun, tau Boo.smagnetic cycle has a duration of only two years. In the previous AO, we wereawarded four EPIC pointings of 8 ks each to monitor tau Boo.s activity inXrays, backing up our observations with optical measurements of thechromospheric activity as well as Zeeman Doppler Imaging. We propose to continuemonitoring the star during this AO with XMMNewton for a total of 32 ks as wellas with Chandra for a total of 10 ks to gain more insight into the stellaractivity cycle by comparing Xray luminosities and coronal temperatures derivedfrom the CCD spectra to the chromospheric activity profile and the magnetic field configuration of tau Boo. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]