Twenty Years of Searching for (and Finding) Globular Cluster Pulsars

Abstract

Globular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered twenty years ago, at least 138 have been identified - most of which are binary millisecond pulsars. Because of their origins involving stellar encounters, many of these systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the mass distribution of neutron stars, and the dynamics of globular clusters.