Polarimetry of millisecond pulsars

The mean polarization profiles of several fast pulsars were measured. Observations of pulsar PSR 1937 + 21 are similar to previously published results, except that a shallower position angle was found to swing across the pulse at low frequency; for the first time, the occurrence of orthogonal mode switching at all frequencies is explicitly demonstrated. Contrary to previous reports, it is shown that PSR 1953 + 29 is substantially linearly polarized in its first and third components. In addition, the first polarization measurements of the recently discovered millisecond pulsar PSR 1957 + 20 are presented. No evidence is found that the polarization properties of these recycled pulsars differ from those of their slower counterparts. Available data on the spectral development of millisecond pulsar profiles is also reviewed. It is emphasized that millisecond pulsars severely test phenomenological models such as the one proposed by Rankin (1983, 1990). 27 refs