Colloquium: Dynamic Pulsar Timing Array data combinations

© Rutger van Haasteren

Pulsar Timing Array (PTA) projects have published the first signs of a stochastic background of gravitational waves. Combined data from all PTAs are expected to yield much larger detection significance. However, combining data from all PTAs has historically been a time-consuming task, and the current International PTA (IPTA) data combination project is a multi-year endeavor with involvement of more than 100 scientists. In this presentation I present a different approach, where we can avoid the data combination step while still maintaining the same sensitivity to gravitational waves. I also show that currently used uninformative priors for the noise parameters are not appropriate, because they cause bias in inferred gravitational wave parameters. Instead a Hierarchical Bayesian Model (HBM) should be used. All currently published PTA GW results will have to be revisited with Hierarchical Models.