What are Pulsars?

A pulsar is a rapidly rotating neutron star. A neutron star is one of the end points of the life of a massive star, after it explodes in a supernova explosion. A neutron star which retains a strong magnetic field produces pulses of radiation along that field. This magnetic field is not aligned with the rotation axis of the the neutron star. We observe these pulses of radiation whenever the magnetic pole is visible. The pulses come at the same rate as the rotation of the neutron star, and, thus, appear periodic. Neutron stars for which we see such pulses are called "pulsars".

How does X-ray astronomy fit in?

Pulsars were first discovered through their emission at radio wavelengths. But pulsars also emit x-ray and gamma ray radiation. It starts with electrons which are accelerated near the magnetic poles of the neutron star. These electrons travel outward from the neutron star, until they reach the point at which they would be forced to travel faster than the speed of light to still co-rotate with the star. At this radius, the electrons must stop, and they release some of their energy in the form of X-rays and gamma-rays. From studying this high energy radiation, we can learn about the strength of the magnetic field, the inner structure of the pulsar, the region surrounding the pulsar, and in some systems the mass of the neutron star.

Crab Nebula reference page

Further Pulsar Resources and References