Are we there yet? Time to detection of nanohertz gravitational waves based on pulsar-timing array limits

Abstract

Decade-long timing observations of arrays of millisecond pulsars have placed highly constraining upper limits on the amplitude of the nanohertz gravitational-wave stochastic signal from the mergers of supermassive black-hole binaries ($\sim 10^{-15}$ strain at $f=1/\mathrm{yr}$). These limits suggest that binary merger rates have been overestimated, or that environmental influences from nuclear gas or stars accelerate orbital decay, reducing the gravitational-wave signal at the lowest, most sensitive frequencies. This prompts the question whether nanohertz gravitational waves are likely to be detected in the near future. In this letter, we answer this question quantitatively using simple statistical estimates, deriving the range of true signal amplitudes that are compatible with current upper limits, and computing expected detection probabilities as a function of observation time. We conclude that small arrays consisting of the pulsars with the least timing noise, which yield the tightest upper limits, have discouraging prospects of making a detection in the next two decades. By contrast, we find large arrays are crucial to detection because the quadrupolar spatial correlations induced by gravitational waves can be well sampled by many pulsar pairs. Indeed, timing programs which monitor a large and expanding set of pulsars have an $\sim 80\%$ probability of detecting gravitational waves within the next ten years, under assumptions on merger rates and environmental influences ranging from optimistic to conservative. Even in the extreme case where $90\%$ of binaries stall before merger and environmental coupling effects diminish low-frequency gravitational-wave power, detection is delayed by at most a few years.

7 pages, 3 figures, 1 table. Published in ApJ Letters

References in corpus (13)

• Observation of Gravitational Waves from a Binary Black Hole Merger
• European Pulsar Timing Array Limits On An Isotropic Stochastic Gravitational-Wave Background
• The stochastic gravitational-wave background from massive black hole binary systems: implications for observations with Pulsar Timing Arrays
• Gravitational waves from binary supermassive black holes missing in pulsar observations
• Expected properties of the first gravitational wave signal detected with pulsar timing arrays
• The NANOGrav Nine-year Data Set: Observations, Arrival Time Measurements, and Analysis of 37 Millisecond Pulsars
• On measuring the gravitational-wave background using Pulsar Timing Arrays
• Mapping gravitational-wave backgrounds using methods from CMB analysis: Application to pulsar timing arrays
• Time-domain Implementation of the Optimal Cross-Correlation Statistic for Stochastic Gravitational-Wave Background Searches in Pulsar Timing Data
• LEAP: the large European array for pulsars
• Binary super-massive black hole environments diminish the gravitational-wave signal in the pulsar timing band
• Constraining the Solution to the Last Parsec Problem with Pulsar Timing
• Testing general relativity with gravitational waves: a reality check

Cited by in corpus (83)

• Search for an isotropic gravitational-wave background with the Parkes Pulsar Timing Array
• Black holes, gravitational waves and fundamental physics: a roadmap
• The NANOGrav 11-year Data Set: High-precision timing of 45 Millisecond Pulsars
• Detection methods for stochastic gravitational-wave backgrounds: a unified treatment
• The NANOGrav 11-year Data Set: Pulsar-timing Constraints On The Stochastic Gravitational-wave Background
• The International Pulsar Timing Array: Second data release
• The Astrophysics of Nanohertz Gravitational Waves
• Selection bias in dynamically-measured super-massive black hole samples: its consequences and the quest for the most fundamental relation
• Massive Black Hole Binary Mergers in Dynamical Galactic Environments
• PINT: A Modern Software Package for Pulsar Timing
• The Local Nanohertz Gravitational-Wave Landscape From Supermassive Black Hole Binaries
• The Gravitational Wave Background from Massive Black Hole Binaries in Illustris: spectral features and time to detection with pulsar timing arrays
• The NANOGrav 12.5 yr Data Set: Observations and Narrowband Timing of 47 Millisecond Pulsars
• Astrophysics Milestones For Pulsar Timing Array Gravitational Wave Detection
• Single Sources in the Low-Frequency Gravitational Wave Sky: properties and time to detection by pulsar timing arrays
• The NANOGrav 12.5-year Data Set: Wideband Timing of 47 Millisecond Pulsars
• Identifying and mitigating noise sources in precision pulsar timing data sets
• Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem
• From Bright Binaries To Bumpy Backgrounds: Mapping Realistic Gravitational Wave Skies With Pulsar-Timing Arrays
• Constraining astrophysical observables of Galaxy and Supermassive Black Hole Binary Mergers using Pulsar Timing Arrays
• Realistic sensitivity curves for pulsar timing arrays
• Post-Newtonian evolution of massive black hole triplets in galactic nuclei -- III. A robust lower limit to the nHz stochastic background of gravitational waves
• All correlations must die: Assessing the significance of a stochastic gravitational-wave background in pulsar-timing arrays
• Selection bias in dynamically-measured super-massive black hole samples: consequences for pulsar timing arrays
• Constraining Sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. III. Candidates from Continued Radial Velocity Tests
• Non-tensorial Gravitational Wave Background in NANOGrav 12.5-Year Data Set
• Searching for continuous Gravitational Waves in the second data release of the International Pulsar Timing Array
• Constraints On The Dynamical Environments Of Supermassive Black-hole Binaries Using Pulsar-timing Arrays
• Efficient computation of the gravitational wave spectrum emitted by eccentric massive black hole binaries in stellar environments
• 3FGL Demographics Outside the Galactic Plane using Supervised Machine Learning: Pulsar and Dark Matter Subhalo Interpretations
• The NANOGrav 12.5-year data set: Search for Non-Einsteinian Polarization Modes in theGravitational-Wave Background
• Discovery of a close-separation binary quasar at the heart of a z~0.2 merging galaxy and its implications for low-frequency gravitational waves
• Gravitational wave research using pulsar timing arrays
• Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction
• Studying the solar system with the International Pulsar Timing Array
• Search for Stochastic Gravitational-Wave Background from Massive Gravity in the NANOGrav 12.5-Year Data Set
• Mapping Incoherent Gravitational Wave Backgrounds
• Common-spectrum process versus cross-correlation for gravitational-wave searches using pulsar timing arrays
• Cross-correlation of the astrophysical gravitational-wave background with galaxy clustering
• The nightmare scenario: measuring the stochastic gravitational-wave background from stalling massive black-hole binaries with pulsar-timing arrays
• The NANOGrav 11-Year Data Set: Evolution of Gravitational Wave Background Statistics
• Fisher formalism for anisotropic gravitational-wave background searches with pulsar timing arrays
• The effect of differential accretion on the Gravitational Wave Background and the present day MBH Binary population
• Evaluating the prevalence of spurious correlations in pulsar timing array datasets
• Insights into searches for anisotropies in the nanohertz gravitational-wave background
• Toward the unambiguous identification of supermassive binary black holes through Bayesian inference
• The NANOGrav 11yr Data Set: Limits on Supermassive Black Hole Binaries in Galaxies within 500Mpc
• Gravitational Wave Detection with Photometric Surveys
• Constraining the Stochastic Gravitational Wave Background with Photometric Surveys
• Robust Estimation of Scattering in Pulsar Timing Analysis
• No tension between assembly models of supermassive black hole binaries and pulsar observations
• The minimum and maximum gravitational-wave background from supermassive binary black holes
• Sensitivity of present and future detectors across the black-hole binary gravitational wave spectrum
• Multi-messenger Approaches to Supermassive Black Hole Binary Detection and Parameter Estimation: Implications for Nanohertz Gravitational Wave Searches with Pulsar Timing Arrays
• Probing supermassive black hole mergers and stalling with pulsar timing arrays
• Radio Scattering Horizons for Galactic and Extragalactic Transients
• Constraining the Graviton Mass with the NANOGrav 15-Year Data Set
• Detectability of Gravitational Waves from High-Redshift Binaries
• Considerations for the Observability of Kinematically Offset Binary AGN
• Ephemeris Errors and the Gravitational Wave Signal: Harmonic Mode Coupling in Pulsar Timing Array Searches
• Optimizing Pulsar Timing Arrays Observations for Detection and Characterization of Low-Frequency Gravitational Wave Sources
• 21st Century Statistical and Computational Challenges in Astrophysics
• Searching for Gravitational Waves with Strongly Lensed Repeating Fast Radio Bursts
• Supermassive Black Hole Binary Environments: Effects on the Scaling Laws and Time to Detection for the Stochastic Background
• An estimate of the stochastic gravitational wave background from the MassiveBlackII simulation
• A Radio Relic and a Search for the Central Black Hole in the Abell 2261 Brightest Cluster Galaxy
• Toward robust detections of nanohertz gravitational waves
• Review of Pulsar Timing Array for Gravitational Wave Research
• Using Gravitational Wave Parallax to Measure the Hubble Parameter with Pulsar Timing Arrays
• Multimessenger Approaches to Supermassive Black Hole Binary Detection and Parameter Estimation II: Optimal Strategies for a Pulsar Timing Array
• Proving the short-wavelength approximation in Pulsar Timing Array gravitational-wave background searches
• 2MASX J00423991+3017515: An offset active galactic nucleus in an interacting system
• Gravitational Wave Statistics for Pulsar Timing Arrays: Examining Bias from Using a Finite Number of Pulsars
• Reducing instrumental errors in Parkes Pulsar Timing Array data
• Astrophysics with the Laser Interferometer Space Antenna
• Impact of the observation frequency coverage on the significance of a gravitational wave background detection in PTA data
• Detailed study of detection method for ultra-low-frequency gravitational waves with pulsar spin-down rate statistics
• Unravelling the formation of the first supermassive black holes with the SKA pulsar timing array
• Precision Timing of PSR J0437-4715 with the IAR Observatory and Implications for Low-Frequency Gravitational Wave Source Sensitivity
• Applying clock comparison methods to pulsar timing observations
• Controlling Outlier Contamination In Multimessenger Time-domain Searches For Supermasssive Binary Black Holes
• On-the-Fly Mapping of New Pulsars
• Spatial Correlation between Pulsars from Interfering Gravitational-Wave Sources in Massive Gravity