The magnetic fields of the AP stars

Abstract

A survey of longitudinal magnetic fields B(e) among bright northern and southern Ap stars is conducted. The photoelectric technique used involves circular Zeeman polarimetry in the wings of H-beta. It is found that the photoelectric B(e) curves tend to be more harmonic than the photographic B(e) curves. Magnetic fields are discovered in several rotating Ap stars. There is marginal evidence to suggest that the rapid rotators might have surface magnetic fields smaller than the slow rotators; however, some very rapid rotators (P equals 0.5 days) can clearly have B(e) extrema comparable to the extrema of slow rotators. Serious evidence is not found for irregular B(e) variations although irregular variations of the order of 200 gauss in some stars cannot be excluded. The astrophysical implications of the findings are briefly discussed.