Radio Emission Properties of Pulsars

¹ Pulsar parameters used in this paper have been obtained from the ATNF Pulsar Catalogue, Version 1.29, http://www.atnf.csiro.au/research/pulsar/psrcat [44]. Pulsars are fascinating objects with a wide range of applications in physics and astronomy. Characterised observationally by a highly periodic pulse train with periodicities typically in the range a few milliseconds to several seconds, they are generally identified with highly magnetised and rapidly rotating neutron stars formed in supernova explosions. Rotation of the star causes beamed emission, probably emanating from open field lines associated with the magnetic poles, to sweep across the sky generating one observed pulse per rotation period. A total of 1,765 pulsars are now known and almost all of these lie within our Galaxy.¹ As Fig. 2.1 illustrates, pulsars come in two main classes, those with periods in the millisecond range and the so-called “normal” pulsars with periods of order 1 s. Most millisecond pulsars (MSPs) are binary, that is, in an orbit with another star, whereas only a few percent of normal pulsars are binary. MSPs, which comprise about 10% of the known population, are believed to be relatively old pulsars which have been spun up or “recycled” by accretion from a binary companion [3]. Because of exchange interactions occurring in their dense cores, globular clusters are a fertile breeding ground for MSPs [10] and about three-quarters of the known MSPs are associated with these clusters.