The NANOGrav 12.5 yr Data Set: Search for an Isotropic Stochastic Gravitational-wave Background

By Z. Arzoumanian, P. Baker, Harsha Blumer, B. Bécsy, A. Brazier, P. Brook, S. Burke-Spolaor, S. Chatterjee, Siyuan Chen, Jim Cordes and 51 more. Astrophysical Journal Letters, 2020

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We search for an isotropic stochastic gravitational-wave background (GWB) in the 12.5 yr pulsar-timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. Our analysis finds strong evidence of a stochastic process, modeled as a power law, with common amplitude and spectral slope across pulsars. Under our fiducial model, the Bayesian posterior of the amplitude for an f −2/3 power-law spectrum, expressed as the characteristic GW strain, has median 1.92 × 10−15 and 5%–95% quantiles of 1.37–2.67 × 10−15 at a reference frequency of fyr=1yr−1; the Bayes factor in favor of the common-spectrum process versus independent red-noise processes in each pulsar exceeds 10,000. However, we find no statistically significant evidence that this process has quadrupolar spatial correlations, which we would consider necessary to claim a GWB detection consistent with general relativity. We find that the process has neither monopolar nor dipolar correlations, which may arise from, for example, reference clock or solar system ephemeris systematics, respectively. The amplitude posterior has significant support above previously reported upper limits; we explain this in terms of the Bayesian priors assumed for intrinsic pulsar red noise. We examine potential implications for the supermassive black hole binary population under the hypothesis that the signal is indeed astrophysical in nature.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/df091430d0b50a4be8371c1b0f8f3b5fb363dda2

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Citations in the corpus

Solar-mass primordial black holes explain NANOGrav hint of gravitational waves (2020, methodology): “The uniform prior on the red noise for each pulsar (adopted in the existing constraints) tends to pre-assign and overestimate the power in red noise components [30], and the reweighting of the samples of the previous data in accordance with the log-uniform prior indeed weaken the previous constraint”
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background (2023, methodology): “An observation following this behavior was reported in 2020 (Arzoumanian et al. 2020, henceforth NG12gwb) for the 12.5-year data set collected by the North American Nanohertz Observatory for Gravitational waves (NANOGrav, McLaughlin 2013; Ransom et al. 2019), and then confirmed (Goncharov et al.…”
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar Timing Array (2023, methodology): “This may be due to high-fluctuationfrequency processes present in the data set, such as unmodeled pulse-shape variations (Shannon et al. 2016; Arzoumanian et al. 2020; Goncharov et al. 2021b).”
Detecting high-frequency gravitational waves with microwave cavities (2021, background): “These include future ground-based [3–5] and space-based [6, 7] laser interferometers, atom interferometers [8–10], pulsar timing arrays [11, 12], and CMB observations [13, 14], as well as new types of astrophysical signatures [15].”
From NANOGrav to LIGO with metastable cosmic strings (2020, methodology): “This allows us to directly translate the one and two sigma confidence intervals given in [7] into the Ω gw−nt plane, as depicted by the orange shaded region in Fig.”
The NANOGrav 15 yr Data Set: Observations and Timing of 68 Millisecond Pulsars (2023, background): “NANOGrav’s most recent GW results for the NG12 data set can be found in Arzoumanian et al. (2020) for the stochastic GWB, Arzoumanian et al. (2021a) for non-Einsteinian polarization modes in the GWB, Arzoumanian et al. (2021b) for constraints on cosmological phase transitions, and Arzoumanian et…”
New physics from the polarized light of the cosmic microwave background (2022, methodology): “We can also measure GW-induced motion of astrophysical bodies such as pulsars 182,183 (rotating neutron stars emitting pulses of radio emission) and stars 184 within our Galaxy to detect GW of λ ≃ tens of light-years (10 − 9 Hz).”
The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background (2023, methodology): “The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5 yr data set showed evidence of a common-spectrum red-noise process consistent with a GWB (Arzoumanian et al. 2020).”
Searching for the Nano-Hertz Stochastic Gravitational Wave Background with the Chinese Pulsar Timing Array Data Release I (2023, methodology): “Our GWB amplitude seems to be compatible with that of the common red signal of other PTAs (Arzoumanian et al. 2020; Chen et al. 2021; Goncharov et al. 2021; Antoniadis et al. 2022), although the median of posterior distribution seems to be 0.4–0.5 dex higher.”