P-Pdot diagram

A P-Pdot diagram is a graph plotting the rates of change of pulsars' rotation periods (Pdot, meaning a dot "." over a P, for period derivative) against their rotation periods (P). The two values characterize a pulsar's rotation evolution, and such a diagram allows comparison and classification of pulsars in this respect, revealing the characteristics and evolution of pulsars in general. Pulsars' periods generally grow at a slow rate, but can occasionally jump to a slightly shorter period (a glitch), presumably due to a significant rearrangement of some of its mass, which could be thought of as a "pulsar quake" or perhaps the collapse of a hill on its surface. They also can reduce their rotation period by gaining angular momentum through accretion from a binary companion. Such diagrams show a clear distinction between pulsars that have a companion versus lone pulsars: those with a companion both have a shorter period and don't slow their rotation as quickly, placing them in a separate, distinct portion of the diagram.