Properties of Pulsars

The correlation of various observed properties of pulsars is discussed with reference to the subdivision of pulsars into three groups on the basis of their mean pulse profile and subpulse phase modulation. Type S pulsars have simple pulse profiles, Type C pulsars have complex pulse shapes with more than one intense component, and Type D pulsars are characterized by drifting-subpulse behavior. It is shown that Type D pulsars are weakly polarized, in contrast to Type C pulsars which generally have a high degree of linear polarization. Type S pulsars have short periods, but may have large or small percentage polarization. For Types C and D the fractional pulse width is large, but for Type S pulsars it appears to be inversely related to the maximum rate of change of position angle through the pulse. The quantity PP,t, which is thought to be proportional to the square of the magnetic-dipole moment, is shown to cover a wide range, with Type C pulsars having large values and Type D pulsars small values. The apparent lack of dependence of Pp* on period implies that the dipole moment is not a function of the pulsar age. The correlations observed suggest that young and short-period pulsars are generally Type S. Then as their period increases, those pulsars with large values of PP*0 evolve to become Type C pulsars, whereas those with small PP values become Type D.