The Gravitational-Wave Discovery Space of Pulsar Timing Arrays

Abstract

Recent years have seen a burgeoning interest in using pulsar timing arrays (PTAs) as gravitational-wave (GW) detectors. To date, that interest has focused mainly on three particularly promising source types: supermassive--black-hole binaries, cosmic strings, and the stochastic background from early-Universe phase transitions. In this paper, by contrast, our aim is to investigate the PTA potential for discovering unanticipated sources. We derive significant constraints on the available discovery space based solely on energetic and statistical considerations: we show that a PTA detection of GWs at frequencies above ~3.e-5 Hz would either be an extraordinary coincidence or violate "cherished beliefs;" we show that for PTAs GW memory can be more detectable than direct GWs, and that, as we consider events at ever higher redshift, the memory effect increasingly dominates an event's total signal-to-noise ratio. The paper includes also a simple analysis of the effects of pulsar red noise in PTA searches, and a demonstration that the effects of periodic GWs in the 10^-8 -- 10^-4.5 Hz band would not be degenerate with small errors in standard pulsar parameters (except in a few narrow bands).

12 pages, 1 figure, submitted to PRD

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• Realistic sensitivity curves for pulsar timing arrays
• NANOGrav Constraints on Gravitational Wave Bursts with Memory
• Detection and localization of single-source gravitational waves with pulsar timing arrays
• Can we observe the QCD phase transition-generated gravitational waves through pulsar timing arrays?
• The NANOGrav 11-Year Data Set: Limits on Gravitational Wave Memory
• Versatile Directional Searches for Gravitational Waves with Pulsar Timing Arrays
• Pulsar Timing Perturbations from Galactic Gravitational Wave Bursts with Memory
• Search for ultralight scalar dark matter with NANOGrav pulsar timing arrays
• Extending the frequency reach of pulsar timing array based gravitational wave search without high cadence observations
• Single-Source Gravitational Wave Limits from the J1713+0747 24-hr Global Campaign
• Implementation of an efficient Bayesian search for gravitational wave bursts with memory in pulsar timing array data