Ori OB1 CP stars magnetic fields. V.

We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2Myr, and the age of subgroup 1a is in the order of 10Myr.

The average root-mean-square magnetic field <Be> (all) for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.