Deep Mixing in Slowly-rotating B Dwarfs: the Possible Role Played by Magnetic Fields

Evolutionary models for massive stars which take into account rotational mixing effects do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. We present a detailed and fully homogeneous non-LTE abundance analysis of a sample of largely unevolved B stars which points to the existence of a population of intrinsically slowly-rotating, yet nitrogen-rich objects contrary to theoretical expectations. These observations are discussed in relation to the boron content and the (weak) magnetic field detected in some targets.