Systematic errors in searches for nanohertz gravitational waves

Abstract

A number of pulsar timing arrays have recently reported preliminary evidence for the existence of a nanohertz frequency gravitational-wave background. These analyses rely on detailed noise analyses, which are inherently complex due to the many astrophysical and instrumental factors that contribute to the pulsar noise budget. We investigate whether realistic systematic errors, stemming from misspecified noise models that fail to capture salient features of the pulsar timing noise, could bias the evidence for gravitational waves. We consider two plausible forms of misspecification: small unmodeled jumps and unmodeled chromatic noise. Using simulated data, we calculate the distribution of the commonly used optimal statistic with no signal present and using plausibly misspecified noise models. By comparing the optimal statistic distribution with the distribution created using ``quasi-resampling'' techniques (such as sky scrambles and phase shifts), we endeavor to determine the extent to which plausible misspecification might lead to a false positive. The results are reassuring: we find that quasi-resampling techniques tend to underestimate the significance of pure-noise datasets. We conclude that recent reported evidence for a nanohertz gravitational-wave background is likely robust to the most obvious sources of systematic errors; if anything, the significance of the signal is potentially underestimated.

8 pages, 10 figures

References in corpus (11)

• The International Pulsar Timing Array second data release: Search for an isotropic Gravitational Wave Background
• On the evidence for a common-spectrum process in the search for the nanohertz gravitational-wave background with the Parkes Pulsar Timing Array
• Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: Inferences in the stochastic gravitational-wave background search
• Assessing the Role of Spin Noise in the Precision Timing of Millisecond Pulsars
• TEMPO2, a new pulsar timing package. III: Gravitational wave simulation
• Identifying and mitigating noise sources in precision pulsar timing data sets
• A pulsar-based timescale from the International Pulsar Timing Array
• Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array
• The disturbance of a millisecond pulsar magnetosphere
• Evaluating the prevalence of spurious correlations in pulsar timing array datasets
• Systematic errors in estimation of gravitational-wave candidate significance

Cited by in corpus (6)

• Charting the Nanohertz Gravitational Wave Sky with Pulsar Timing Arrays
• Choosing suitable noise models for nanohertz gravitational-wave astrophysics
• The NANOGrav 15 yr data set: Posterior predictive checks for gravitational-wave detection with pulsar timing arrays
• Finite Populations & Finite Time: The Non-Gaussianity of a Gravitational Wave Background
• Accurate pulsar timing array residual variances and correlation of the stochastic gravitational wave background
• The NANOGrav 15 yr Data Set: Customized Chromatic Noise Models