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The second data release from the European Pulsar Timing Array: III. Search for gravitational wave signals Chen

Antoniadis, J and Arumugam, P and Arumugam, S and Babak, S and Bagchi, M and Bak Nielsen, A-S and Bassa, CG and Bathula, A and Berthereau, A and Bonetti, M and Bortolas, E and Brook, PR and Burgay, M and Caballero, RN and Chalumeau, A and Champion, DJ and Chanlaridis, S and Chen, S and Cognard, I and Dandapat, S and Deb, D and Desai, S and Desvignes, G and Dhanda-Batra, N and Dwivedi, C and Falxa, M and Ferdman, RD and Franchini, A and Gair, JR and Goncharov, B and Gopakumar, A and Graikou, E and Griebmeier, J-M and Guillemot, L and Guo, YJ and Gupta, Y and Hisano, S and Hu, H and Iraci, F and Izquierdo-Villalba, D and Jang, J and Jawor, J and Janssen, GH and Jessner, A and Joshi, BC and Kareem, F and Karuppusamy, R and Keane, EF and Keith, MJ and Kharbanda, D and Kikunaga, T and Kolhe, N and Kramer, M and Krishnakumar, MA and Lackeos, K and Lee, KJ and Liu, K and Liu, Y and Lyne, AG and McKee, JW and Maan, Y and Main, RA and Mickaliger, MB and Niţu, IC and Nobleson, K and Paladi, AK and Parthasarathy, A and Perera, BBP and Perrodin, D and Petiteau, A and Porayko, NK and Possenti, A and Prabu, T and Quelquejay Leclere, H and Rana, P and Samajdar, A and Sanidas, SA and Sesana, A and Shaifullah, G and Singha, J and Speri, L and Spiewak, R and Srivastava, A and Stappers, BW and Surnis, M and Susarla, SC and Susobhanan, A and Takahashi, K and Tarafdar, P and Theureau, G and Tiburzi, C and Van Der Wateren, E and Vecchio, A and Venkatraman Krishnan, V and Verbiest, JPW and Wang, J and Wang, L and Wu, Z (2023) The second data release from the European Pulsar Timing Array: III. Search for gravitational wave signals Chen. In: Astronomy and Astrophysics, 678 .

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Official URL: https://doi.org/10.1051/0004-6361/202346844


We present the results of the search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using the second data release of the European Pulsar Timing Array (EPTA) for 25 millisecond pulsars and a combination with the first data release of the Indian Pulsar Timing Array (InPTA). A robust GWB detection is conditioned upon resolving the Hellings-Downs angular pattern in the pairwise cross-correlation of the pulsar timing residuals. Additionally, the GWB is expected to yield the same (common) spectrum of temporal correlations across pulsars, which is used as a null hypothesis in the GWB search. Such a common-spectrum process has already been observed in pulsar timing data. We analysed (i) the full 24.7-year EPTA data set, (ii) its 10.3-year subset based on modern observing systems, (iii) the combination of the full data set with the first data release of the InPTA for ten commonly timed millisecond pulsars, and (iv) the combination of the 10.3-year subset with the InPTA data. These combinations allowed us to probe the contributions of instrumental noise and interstellar propagation effects. With the full data set, we find marginal evidence for a GWB, with a Bayes factor of four and a false alarm probability of 4. With the 10.3-year subset, we report evidence for a GWB, with a Bayes factor of 60 and a false alarm probability of about 0.1 (3significance). The addition of the InPTA data yields results that are broadly consistent with the EPTA-only data sets, with the benefit of better noise modelling. Analyses were performed with different data processing pipelines to test the consistency of the results from independent software packages. The latest EPTA data from new generation observing systems show non-negligible evidence for the GWB. At the same time, the inferred spectrum is rather uncertain and in mild tension with the common signal measured in the full data set. However, if the spectral index is fixed at 13/3, the two data sets give a similar amplitude of (2.5 ± 0.7) - 1015 at a reference frequency of 1 yr-1. Further investigation of these issues is required for reliable astrophysical interpretations of this signal. By continuing our detection efforts as part of the International Pulsar Timing Array (IPTA), we expect to be able to improve the measurement of spatial correlations and better characterise this signal in the coming years. © 2023 EDP Sciences. All rights reserved.

Item Type: Journal Article
Publication: Astronomy and Astrophysics
Publisher: EDP Sciences
Additional Information: The copyright for this article belongs to Author.
Keywords: Data handling; Errors; Gravitational effects; Pulsars; Set theory; Signal detection; Software testing; Statistical tests; Stochastic systems, Bayes factor; Data release; Data set; False alarm probability; Gravitational-waves; Methods. Data analysis; Millisecond pulsars; Observing systems; Pulsars: general; Spectra's, Gravity waves
Department/Centre: Others
Date Deposited: 28 Feb 2024 13:15
Last Modified: 28 Feb 2024 13:15
URI: https://eprints.iisc.ac.in/id/eprint/83696

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