Future Prospects for Spectral Characterisation of the Gravitational Wave Background with Pulsar Timing Arrays

Pulsar Timing Arrays may soon detect a nanohertz-frequency gravitational wave background, which is likely dominated by gravitational waves from a population of supermassive black holes binaries. However, the spectrum of the background may encode the dynamics and demographics of the binary population, as well as sub-dominant signatures of gravitational waves from the early universe. In this talk, we present studies of parameter estimation and model selection of the gravitational-wave background over numbers of pulsar and frequencies using rapid and accurate refitting techniques, and show initial investigations into distinguishing a cosmological signal from an astrophysical background.