Science from Pulsar Timing Array Projects

Draft version. The aim of this document will be to describe to non pulsar astronomers the science obtainable from the PPTA and related projects

1.0 Introduction

The Parkes pulsar timing array (PPTA) has three main aims. The first is to make a direct detection of a background of gravitational waves from coalescing supermassive binary black hole systems. The second is to improve the solar system ephemeris and the third the look for irregularities in the terrestrial time standards. In order to achieve this goals, observations are made using the Parkes radio telescope of 20 millisecond radio pulsars at regular intervals (typically every ~2 weeks). The data sets that now span ~2.5 years are already producing interesting scientific results on topics as varied as the Solar corona, the mass of Jupiter and turbulence in the interstellar medium as well as placing stringent limits on the existence of any gravitational wave background. The purpose here is to document the scientific results being obtained by the PPTA (and other related timing array projects) in a way that is understandable to non-pulsar astronomers.

2.0 Terrestrial time standards

3.0 The solar system

3.1 Planetary masses

3.2 The solar corona

4.0 The interstellar medium

5.0 Gravitational waves

5.1 Individual black hole binary systems

5.1.1 3C66B

5.1.2 Sag A*

5.2 Burst sources

5.3 Stochastic gravitational wave backgrounds

5.3.1 Background from coalescing supermassive binary black holes

5.3.2 Background from the inflationary era

5.3.3 Background from cosmic strings

5.4 Other gravitational wave detectors