We present further evidence that the magnetic chemically peculiar stars ( CP2 ) of the upper main sequence already occur at very early stages of the stellar evolution , significantly before they reach 30 % of their life-time on the main sequence .
This result is especially important for models dealing with dynamo theories , angular momentum loss during the pre- as well as main sequence and evolutionary calculations for CP2 stars .
Results from the literature either derived for objects in the Hyades and the UMa cluster or from the Hipparcos mission contradict each other .
A way out of this dilemma is to investigate young open clusters with known ages and accurate distances ( error < 10 % ) , including CP2 members .
Up to now , four open clusters fulfill these requirements : IC 2391 , IC 2602 , NGC 2451 A and NGC 2516 .
In total , 13 CP2 stars can be found within these clusters .
We have used the measurements and calibrations of the Geneva 7-color photometric system to derive effective temperatures and luminosities .
Taking into account the overall metallicity of the individual clusters , isochrones and evolutionary tracks were used to estimate ages and masses for the individual objects .
The derived ages ( between 10 and 140 Myr ) are well in line with those of the corresponding clusters and further strengthen the membership of the investigated CP2 stars .