Figure 1.

Measured magnetic fields in a sample of Ap stars in which either no magnetic field had yet been detected or in which there had been an ambiguous or borderline detection. In this study, the detection limit is only a few gauss; every star in the sample is found to have a magnetic field much stronger than this. The dashed line represents the cut-off at 300 G. This result confirms convincingly that all Ap-type chemically peculiar stars have strong magnetic fields. By contrast, other A stars have never been found to have any magnetic field above a few gauss; there is a clear bimodality. From Aurière et al. [11].