Pulsars

As a rapidly spinning young neutron star (a "pulsar") slows down, it deposits its enormous reservoir of rotational energy into its environment via a relativistic wind, producing an observable pulsar wind nebula (PWN). PWNe are a rich source of information. Most fundamentally, they provide a direct probe of the high-energy processes through which a neutron star's considerable reservoir of rotational energy is eventually deposited into its environment. In addition, because many PWNe are close enough to be spatially resolved, they provide an excellent laboratory for studying the process through which a rotating compact object couples to its environment, a theme now also emerging in modeling of gamma-ray bursts and their afterglows. Finally, the presence of a PWN unambiguously points to the presence of a central neutron star, even when the latter cannot be directly detected. PWNe are thus good signposts in the ongoing search for the youngest and most energetic neutron stars. Through a diverse X-ray, radio and optical program focused on using PWNe as probes of the interaction between pulsars and their environments, we hope to provide a detailed physical basis for understanding the processes through which pulsars accelerate relativistic particles and interact with their surroundings.