The European Pulsar Timing Array
Published June 29, 2023 | Version 2.0
Dataset Open

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

Creators

  • 1. Institute of Astrophysics, FORTH, N. Plastira 100, 70013, Heraklion, Greece
  • 2. Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, India
  • 3. Department of Electrical Engineering, IIT Hyderabad, Kandi, Telangana 502284, India
  • 4. Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France
  • 5. The Institute of Mathematical Sciences, C. I. T. Campus, Taramani, Chennai 600113, India
  • 6. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
  • 7. ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
  • 8. Department of Physical Sciences, Indian Institute of Science Education and Research, Mohali, Punjab 140306, India
  • 9. Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, Université d'Orléans / CNRS, 45071 Orléans Cedex 02, France
  • 10. Dipartimento di Fisica "G. Occhialini", Universitá degli Studi di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy
  • 11. Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 992TT, UK
  • 12. INAF - Osservatorio Astronomico di Cagliari, via della Scienza 5, 09047 Selargius (CA), Italy
  • 13. Hellenic Open University, School of Science and Technology, 26335 Patras, Greece
  • 14. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, P. R. China
  • 15. Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Navy Nagar, Colaba, Mumbai 400005, India
  • 16. Department of Physics, IIT Hyderabad, Kandi, Telangana 502284, India
  • 17. Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India
  • 18. Department of Earth and Space Sciences, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala 695547,India
  • 19. School of Physics, Faculty of Science, University of East Anglia, Norwich NR4 7TJ, UK
  • 20. Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, 14476 Potsdam, Germany
  • 21. Gran Sasso Science Institute (GSSI), I-67100 L'Aquila, Italy
  • 22. National Centre for Radio Astrophysics, Pune University Campus, Pune 411007, India
  • 23. Kumamoto University, Graduate School of Science and Technology, Kumamoto, 860-8555, Japan
  • 24. Department of Physical Sciences,Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
  • 25. School of Physics, Trinity College Dublin, College Green, Dublin 2, D02 PN40, Ireland
  • 26. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
  • 27. Department of Physics, St. Xavier's College (Autonomous), Mumbai 400001, India
  • 28. Department of Astronomy,School of Physics, Peking University, Beijing 100871, P. R. China
  • 29. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, P. R. China
  • 30. E.A. Milne Centre for Astrophysics, University of Hull, Cottingham Road, Kingston-upon-Hull, HU6 7RX, UK
  • 31. Department of Physics, BITS Pilani Hyderabad Campus, Hyderabad 500078, Telangana, India
  • 32. Joint Astronomy Programme, Indian Institute of Science, Bengaluru, Karnataka, 560012, India
  • 33. Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USA
  • 34. IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
  • 35. Raman Research Institute India, Bengaluru, Karnataka, 560080, India
  • 36. Institut für Physik und Astronomie, Universität Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany
  • 37. Department of Physics, IISER Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462066, Madhya Pradesh, India
  • 38. Ollscoil na Gaillimhe — University of Galway, University Road, Galway, H91 TK33, Ireland
  • 39. Center for Gravitation, Cosmology, and Astrophysics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
  • 40. Division of Natural Science, Faculty of Advanced Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
  • 41. Florida Space Institute, University of Central Florida, 12354 Research Parkway, Partnership 1 Building, Suite 214, Orlando, 32826-0650, FL, USA
  • 42. Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany

Description

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% (≳ 3σ significance). 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) × 10−15 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.

Notes

Data for EPTA DR2 paper 3.

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Additional details

Related works

Is derived from
10.1051/0004-6361/202346841 (DOI)
10.5281/zenodo.8164425 (DOI)
Is source of
10.1051/0004-6361/202346844 (DOI)
Is supplemented by
10.5281/zenodo.8025019 (DOI)
Requires
10.1051/0004-6361/202346842 (DOI)