Discovery and Characterization of Superefficiency in Pulsar Wind Nebulae

We numerically study the radiative properties of the reverberation phase of pulsar wind nebulae. Reverberation brings a significant evolution in a short period of time. We show that even the Crab Nebula, associated with the more energetic pulsar of the sample that we consider, has a period in its future time evolution where the X-ray luminosity will exceed the spin-down power at the time. In fact, all of the nebulae in our sample are expected to have a period of radio, X-ray, and GeV superefficiency, and most will also have a period of TeV superefficiency. We analyze and characterize these superefficient phases.