Software for a new era of precision pulsar timing

The Parkes Pulsar Timing Array project aims to detect the signatures of gravitational waves in pulsar timing residuals. This requires that pulse arrival times at the Observatory be measured with a random uncertainty of 100 nanoseconds or less. Systematic effects should ideally be kept below one nanosecond. This is an extremely difficult challenge for both observing systems and for data analysis programs.

We have developed TEMPO2, a new pulsar timing package that computes all relevant timing corrections to an accuracy of one nanosecond or better. TEMPO2 is also compliant with the IAU 2000 resolutions on time systems and hence uses up-to-date precession-nutation and polar-motion models, the International Celestial Reference System and Barycentric Coordinate Time. It includes new algorithms to calculate, for example, delays due to the general relativisitic time dilation (Shapiro delay) as a pulse passes the giant planets, second-order Solar Shapiro delay and various atmospheric effects.

The TEMPO2 package includes various analysis and visualisation tools. These include computing and displaying periodograms of the timing residuals, correlating the residuals between different pulsars and graphing the various correction terms computed by TEMPO2. It is also relatively straightforward to develop new "plug-ins" for TEMPO2. Astronomers around the world are already adding features such as a multi-resolution CLEAN deconvolution algorithm and periodicity searches. The TEMPO2 software can be obtained from the webpage www.atnf.csiro.au/research/pulsar/tempo2.

We are currently writing three papers that should be submitted shortly. The first contains an overview of the TEMPO2 software and discusses the differences between this software and earlier pulsar timing packages. The second paper contains full details of the timing model and the third describes the use of TEMPO2 for fitting timing solutions to data for multiple pulsars simultaneously and for investigating correlations in the timing data for different pulsars.

TEMPO2 will supersede all existing pulsar timing packages and provide the accuracy needed for pulsar timing into and beyond the SKA era. It will be an essential part of our effort to make what may be the first direct detection of gravity waves.

George Hobbs, Russell Edwards and Richard Manchester
((George.Hobbs@csiro.au, Russell.Edwards@csiro.au and Dick.Manchester@csiro.au)