The magnetic chemically peculiar ( mCP ) stars of the upper main sequence exhibit strong , globally organized magnetic fields that are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability .
Therefore , mCP stars are perfectly suited for a direct measurement of the rotational period without the need for any additional calibrations .
We have investigated the rotational properties of mCP stars based on an unprecedentedly large sample consisting of more than 500 objects with known rotational periods .
Using precise parallaxes from the Hipparcos and Gaia satellite missions , well-established photometric calibrations and state-of-the-art evolutionary models , we have determined the location of our sample stars in the Hertzsprung-Russell diagram and derived astrophysical parameters such as stellar masses , effective temperature , radii , inclinations and critical rotational velocities .
We have confirmed the conservation of angular momentum during the main sequence evolution ; no signs of additional magnetic braking were found .
The inclination angles of the rotational axes are randomly distributed , although an apparent excess of fast rotators with comparable inclination angles has been observed .
We have found a rotation rate of \upsilon / \upsilon _ { crit } \geq 0.5 for several stars , whose characteristics can not be explained by current models .
For the first time , we have derived the relationship between mass and rotation rate of mCP stars , and provide an analysis that links mass and rotation with magnetic field strength .
Our sample is unique and offers crucial input for forthcoming evolutionary models that include the effects of magnetic fields for upper main sequence stars .