David Champion (Australia Telescope National Facility)

The Discovery of an Eccentric Millisecond Pulsar in the Galactic Plane - David Champion Colloquium

ATNF Marsfield Lecture Theatre

Abstract

The evolution of binary systems is governed by their orbital properties and the stellar density of the local environment. Studies of neutron stars in binary star systems offer unique insights into both these issues. In an Arecibo survey of the Galactic disk, we have found PSR J1903+0327, a pulsar with a 2.15-ms rotation period, in a 95-day orbit around a massive companion. Observations in the infra-red suggests that the companion may be a main-sequence star. Theories requiring an origin in the Galactic disk cannot account for the extraordinarily high orbital eccentricity observed (0.44) or a main-sequence companion of a pulsar that has spin properties suggesting a prolonged accretion history. Alternative formation scenarios involve recycling a neutron star in a globular cluster then ejecting it into the Galactic disk, or membership in a hierarchical triple system. Radio timing suggests that the pulsar mass is 1.81 ± 0.09 Msun, an unusually high value.