AA manuscript no.

Landstreet & Mathys (2000) have discovered that almost all the magnetic Ap stars having rotation periods longer than about one month have their magnetic and rotation axes fairly closely aligned, in contrast to the more common magnetic Ap stars of shorter period, in which the two axes are usually inclined to one another at a large angle. Furthermore, as shown earlier by Mathys et al. (1997) and by Hubrig et al. (2000), these most slowly rotating magnetic Ap stars have also magnetic fields several times larger than are typical for shorter period magnetic Ap stars, and generally have masses below 3 M