alpha Persei
Carina nebula
Carina nebula
Eta Car nebula
Hyades
IC1805
M 34
M 55, omega cen, M 22, NGC 3201, ...
NGC 2264
NGC 6231
NGC6231
NGC6383
Pleiades
Praesepe
Several stellar clusters
sigma Orionis
WR 142
Stellar ClustersStellar clusters provide homogeneous samples of stars with approximately the same age and chemical composition but different masses, temperatures, rotation rates and magnetic activity. By observing stars in different clusters it is thus possible to investigate the dependence of coronal X-ray emission upon rotation and age and to test models of stellar magnetic activity and internal dynamo action. Previous X-ray missions (especially EINSTEIN and ROSAT) have allowed a first glimpse at the activity-rotation-age relationship in cluster stars and have shown that, on average, coronal activity in late-type stars decreases as a star gets older and rotates more slowly. The details of this relationship, however, are far from being understood thus limiting our ability to model the mechanisms of magnetic field generation and dynamo activity in stars. XMM-Newton can provide crucial data on this issue by going much deeper in sensitivity than previous satellites and providing spectral data for the brighter cluster members. |