Millisecond Pulsars: A New Population of Gamma Ray Sources?

Abstract

Pulsars have a pride of place in gamma ray astronomy. This is as it should be! For, after all, the Crab and Vela pulsars are the best studied gamma ray sources. These observations, in turn, have sparked renewed activity in trying to understand how pulsars work. The early attempts concentrated on the generation of the coherent radio radiation through which they were first detected. The energy in this radiation is, however, an extremely small fraction of the rotational energy loss of the pulsar most of which is believed to be carried away by an ultrarelativistic electron-positron wind with a frozen-in magnetic field. But there is no consensus as yet regarding HOW these particles are accelerated, or WHERE the accelerator is located. This is where the importance of the detailed gamma ray observations of pulsars lies. There are reasons to think that the electron-positron pair production and their acceleration, and the observed gamma ray emission may be from the same region, or nearby regions of the magnetosphere. Thus, in an indirect way, the pulsed gamma rays are telling us something about the location of the particle accelerator.