Detection of Gravitational Waves with Pulsar Timing

Richard N Manchester
(Australia Telescope National Facility, CSIRO)


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Millisecond pulsars have extremely stable periods and small perturbations in the observed periods due to gravitational waves (GW) passing over the Earth and the pulsar can in principle be detected. Observations of just a few pulsars can only ever put a limit on the strength of GW in the Galaxy, but a positive detection can be made with observations of many pulsars spread across the celestial sphere, a so-called “Pulsar Timing Array” (PTA). PTAs are sensitive to GW with frequencies in the nanoHertz range and hence are complementary to ground- and space-based laser-interferometer systems. The Parkes Pulsar Timing Array (PPTA) project has been timing 20 millisecond pulsars for about four years with steadily improving technology and similar PTA systems are under development in North America (NANOGrav) and Europe (EPTA). These PTAs should detect predicted levels of the stochastic GW background from binary super-massive black holes in the cores of distant galaxies in 5 – 10 years. Failure to detect this GW background will have a significant impact on merger models for the growth of galaxies and their central black holes and on models for cosmic-string formation in the early Universe.