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

Chen, S., Caballero, R. N., Guo, Y. J., Chalumeau, A., Liu, K., Shaifullah, G., Lee, K. J., Babak, S., Desvignes, G., Parthasarathy, A., Hu, H., van der Wateren, E., Antoniadis, J., Bak Nielsen, A. S., Bassa, C. G., Berthereau, A., Burgay, M., Champion, D. J., Cognard, I., Falxa, M., Ferdman, R. D. ORCID:, Freire, P. C. C., Gair, J. R., Graikou, E., Guillemot, L., Jang, J., Janssen, G. H., Karuppusamy, R., Keith, M. J., Kramer, M., Liu, X. J., Lyne, A. G., Main, R. A., Mckee, J. W., Mickaliger, M. B., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, A., Sanidas, S. A., Sesana, A., Speri, L., Stappers, B. W., Theureau, G., Tiburzi, C., Vecchio, A., Verbiest, J. P. W., Wang, J., Wang, L. and Xu, H. (2021) Common-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background search. Monthly Notices of the Royal Astronomical Society, 508 (4). pp. 4970-4993. ISSN 0035-8711

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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 yr. 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, ENTERPRISE, and TEMPONEST+FORTYTWO, 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 × 10-15 and γ = 3.78-0.59 +0.69 (95 per cent credible regions). Fixing the spectral index to γ= 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 × 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.

Item Type: Article
Uncontrolled Keywords: gravitational waves,methods: data analysis,pulsars: general,astrophysics - high energy astrophysical phenomena,astrophysics - cosmology and nongalactic astrophysics,astronomy and astrophysics,space and planetary science ,/dk/atira/pure/subjectarea/asjc/3100/3103
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Depositing User: LivePure Connector
Date Deposited: 27 Jul 2023 10:30
Last Modified: 27 Jul 2023 11:30
DOI: 10.1093/mnras/stab2833

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