Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: Inferences in the stochastic gravitational-wave background search

By S. Chen, R. N. Caballero, Y. J. Guo, A. Chalumeau, K.Liu, G. Shaifullah, K. Lee, Stanislav Babak, G. Desvignes, A. Parthasarathy and 42 more. 2021

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We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 years. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power-law with $A = 5.13_{-2.73}^{+4.20} \times 10^{-15}$ and $\gamma = 3.78_{-0.59}^{+0.69}$ (95\% credible regions). Fixing the spectral index to $\gamma=13/3$ as expected from the GWB by circular, inspiralling supermassive black-hole binaries results in an amplitude of $A =2.95_{-0.72}^{+0.89} \times 10^{-15}$. We implement three different models, BAYESEPHEM, LINIMOSS and EPHEMGP, to address possible Solar-system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/241a73765b4dea9a374a506375bdfee348d300cc

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Citations in the corpus

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.”
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar Timing Array (2023, methodology): “Inference and PTA likelihood We use Bayesian inference1 to search for and characterize noise and signals in our data set, following previous PTA analyses (Arzoumanian et al. 2020; Goncharov et al. 2021a; Chen et al. 2021; Antoniadis et al. 2022).”
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background (2023, methodology): “Subsequent independent analyses by the PPTA and EPTA collaborations reported results consistent with ours (Goncharov et al. 2021a; Chen et al. 2021), as did the search of a combined data set (Antoniadis et al. 2022)—a syzygy of tantalizing discoveries that portend the rise of low-frequency GW…”
The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background (2023, background): “…of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. the Parkes Pulsar Timing Array (PPTA; Goncharov et al. 2021), the European Pulsar Timing Array (Chen et al. 2021), and the International Pulsar Timing Array (IPTA; Antoniadis et al. 2022).”
The NANOGrav 15 yr Data Set: Observations and Timing of 68 Millisecond Pulsars (2023, background): “Other PTA collaborations include the European PTA (EPTA; Chen et al. 2021), the Parkes PTA (PPTA; Reardon et al. 2021), and the Indian PTA (InPTA; Tarafdar et al. 2022).”