Gravitational Wave Searches with Pulsar Timing Arrays. I: Cancellation of Clock and Ephemeris Noises

TL;DR

This paper introduces a novel data processing method for pulsar timing arrays that cancels clock and ephemeris noises, significantly improving the sensitivity to gravitational waves and enhancing stochastic background detection.

Contribution

The paper presents a new technique to cancel dominant correlated noises in pulsar timing data, boosting gravitational wave detection sensitivity and stochastic background search capabilities.

Findings

Sensitivity to single-source gravitational waves increased by over an order of magnitude.

Optimal SNR for stochastic background detection improved by more than tenfold.

Proposed noise cancellation method outperforms direct data processing approaches.

Abstract

We propose a data processing technique to cancel monopole and dipole noise sources (such as clock and ephemeris noises respectively) in pulsar timing array searches for gravitational radiation. These noises are the dominant sources of correlated timing fluctuations in the lower-part ($ \approx 10^{-9} - 10^{-8}$ Hz) of the gravitational wave band accessible by pulsar timing experiments. After deriving the expressions that reconstruct these noises from the timing data, we estimate the gravitational wave sensitivity of our proposed processing technique to single-source signals to be at least one order of magnitude higher than that achievable by directly processing the timing data from an equal-size array. Since arrays can generate pairs of clock and ephemeris-free timing combinations that are no longer affected by correlated noises, we implement with them the cross-correlation statistic to search for an isotropic stochastic gravitational wave background. We find the resulting optimal signal-to-noise ratio to be more than one order of magnitude larger than that obtainable by correlating pairs of timing data from arrays of equal size.