CERN Accelerating science

Article
Report number	arXiv:2201.03980
Title	The International Pulsar Timing Array second data release: Search for an isotropic Gravitational Wave Background
Author(s)	Antoniadis, J. (FORTH, Heraklion ; Bonn, Max Planck Inst., Radioastron. ; Argelander Inst. Astron.) ; Arzoumanian, Z. (NASA, Goddard) ; Babak, S. (APC, Paris) ; Bailes, M. (Swinburne U. Tech., Hawthorn ; ARC, CoEPP, Australia) ; Nielsen, A.-S. Bak (Bonn, Max Planck Inst., Radioastron. ; Bielefeld U.) ; Baker, P.T. (Widener U.) ; Bassa, C.G. (ASTRON, Dwingeloo) ; Becsy, B. (Montana State U.) ; Berthereau, A. (LPC2E, Orleans ; Station Radioastronomy, Nancay) ; Bonetti, M. (Milan Bicocca U. ; INFN, Milan Bicocca) ; Brazier, A. (Cornell U.) ; Brook, P.R. (West Virginia U.) ; Burgay, M. (Cagliari Observ.) ; Burke-Spolaor, S. (West Virginia U. ; Canadian Inst. Advanced Res.) ; Caballero, R.N. (Chicago U., KICP) ; Casey-Clyde, J.A. (Connecticut U.) ; Chalumeau, A. (APC, Paris) ; Champion, D.J. (Bonn, Max Planck Inst., Radioastron.) ; Charisi, M. (Vanderbilt U.) ; Chatterjee, S. (Cornell U.) ; Chen, S. (LPC2E, Orleans ; Station Radioastronomy, Nancay) ; Cognard, I. (LPC2E, Orleans ; Station Radioastronomy, Nancay) ; Cordes, J.M. (Cornell U.) ; Cornish, N.J. (Montana State U.) ; Crawford, F. (Franklin - Marshall Coll.) ; Cromartie, H.T. (Cornell U. ; NASA, Marshall) ; Crowter, K. (British Columbia U.) ; Dai, S. (Western Sydney U., Penrith) ; DeCesar, M.E. (George Mason U.) ; Demorest, P.B. (NRAO, Socorro) ; Desvignes, G. (Bonn, Max Planck Inst., Radioastron. ; LESIA, Meudon) ; Dolch, T. (Hillsdale Coll. ; Eureka Sci.) ; Drachler, B. (Rochester Inst. Tech.) ; Falxa, M. (APC, Paris) ; Ferrara, E.C. (Maryland U. ; NASA, Goddard) ; Fiore, W. (West Virginia U.) ; Fonseca, E. (West Virginia U.) ; Gair, J.R. (Potsdam, Max Planck Inst.) ; Garver-Daniels, N. (West Virginia U.) ; Goncharov, B. (GSSI, Aquila ; Gran Sasso) ; Good, D.C. (British Columbia U.) ; Graikou, E. (Bonn, Max Planck Inst., Radioastron.) ; Guillemot, L. (LPC2E, Orleans ; Station Radioastronomy, Nancay) ; Guo, Y.J. (Bonn, Max Planck Inst., Radioastron.) ; Hazboun, J.S. (Washington U., Seattle) ; Hobbs, G. (Australia, CSIRO, Epping) ; Hu, H. (Bonn, Max Planck Inst., Radioastron.) ; Islo, K. (Wisconsin U., Milwaukee) ; Janssen, G.H. (ASTRON, Dwingeloo ; Nijmegen U., IMAPP) ; Jennings, R.J. (Cornell U.) ; Johnson, A.D. (Wisconsin U., Milwaukee) ; Jones, M.L. (Wisconsin U., Milwaukee) ; Kaiser, A.R. (West Virginia U.) ; Kaplan, D.L. (Wisconsin U., Milwaukee) ; Karuppusamy, R. (Bonn, Max Planck Inst., Radioastron.) ; Keith, M.J. (Jodrell Bank) ; Kelley, L.Z. (Northwestern U. (main)) ; Kerr, M. (Naval Research Lab, Wash., D.C.) ; Key, J.S. (Washington U., Seattle) ; Kramer, M. (Bonn, Max Planck Inst., Radioastron. ; Jodrell Bank) ; Lam, M.T. (Rochester Inst. Tech.) ; Lamb, W.G. (Vanderbilt U.) ; Lazio, T.J.W. (Caltech, JPL) ; Lee, K.J. (Peking U., Beijing, KIAA ; NAOC, Beijing ; Bonn, Max Planck Inst., Radioastron.) ; Lentati, L. (Cambridge U.) ; Liu, K. (Bonn, Max Planck Inst., Radioastron.) ; Luo, J. (Toronto U., Astron. Dept.) ; Lynch, R.S. (NRAO, Green Bank) ; Lyne, A.G. (Jodrell Bank) ; Madison, D.R. (U. Pacific, Stockton) ; Main, R.A. (Bonn, Max Planck Inst., Radioastron.) ; Manchester, R.N. (Australia, CSIRO, Epping) ; McEwen, A. (Wisconsin U., Madison) ; McKee, J.W. (Canadian Inst. Theor. Astrophys.) ; McLaughlin, M.A. (West Virginia U.) ; Mickaliger, M.B. (Jodrell Bank) ; Mingarelli, C.M.F. (Flatiron Inst., New York ; Connecticut U.) ; Ng, C. (U. Toronto, Dunlap Inst. Astron. Astrophys.) ; Nice, D.J. (Lafayette Coll.) ; Oslowski, S. (Lab. Astrophysics, Jena) ; Parthasarathy, A. (Bonn, Max Planck Inst., Radioastron.) ; Pennucci, T.T. (Eotvos U.) ; Perera, B.B.P. (Arecibo Observ.) ; Perrodin, D. (Cagliari Observ.) ; Petiteau, A. (APC, Paris) ; Pol, N.S. (Vanderbilt U.) ; Porayko, N.K. (Bonn, Max Planck Inst., Radioastron.) ; Possenti, A. (Cagliari Observ. ; Cagliari U.) ; Ransom, S.M. (NRAO, Charlottesville) ; Ray, P.S. (Naval Research Lab, Wash., D.C.) ; Reardon, D.J. (Swinburne U. Tech., Hawthorn ; ARC, CoEPP, Australia) ; Russell, C.J. (Australia, CSIRO, Melbourne) ; Samajdar, A. (Milan Bicocca U.) ; Sampson, L.M. (Northwestern U.) ; Sanidas, S. (Jodrell Bank) ; Sarkissian, J.M. (Australia, CSIRO, Epping) ; Schmitz, K. (CERN) ; Schult, L. (Vanderbilt U.) ; Sesana, A. (Milan Bicocca U. ; INFN, Milan Bicocca) ; Shaifullah, G. (Milan Bicocca U. ; INFN, Milan Bicocca) ; Shannon, R.M. (Swinburne U. Tech., Hawthorn ; ACQAO, Acton) ; Shapiro-Albert, B.J. (West Virginia U.) ; Siemens, X. (Oregon State U. ; Wisconsin U., Milwaukee) ; Simon, J. (Caltech, JPL ; U. Colorado, Boulder) ; Smith, T.L. (Swarthmore Coll.) ; Speri, L. (Potsdam, Max Planck Inst.) ; Spiewak, R. (Jodrell Bank ; Swinburne U. Tech., Hawthorn ; ACQAO, Acton) ; Stairs, I.H. (British Columbia U.) ; Stappers, B.W. (Jodrell Bank) ; Stinebring, D.R. (Oberlin Coll.) ; Swiggum, J.K. (Lafayette Coll.) ; Taylor, S.R. (Vanderbilt U.) ; Theureau, G. (LPC2E, Orleans ; Station Radioastronomy, Nancay) ; Tiburzi, C. (ASTRON, Dwingeloo) ; Vallisneri, M. (Caltech, JPL ; Caltech, Pasadena (main)) ; van der Wateren, E. (ASTRON, Dwingeloo ; Nijmegen U., IMAPP) ; Vecchio, A. (Birmingham U.) ; Verbiest, J.P.W. (Bielefeld U. ; Bonn, Max Planck Inst., Radioastron.) ; Vigeland, S.J. (Wisconsin U., Milwaukee) ; Wahl, H. (West Virginia U.) ; Wang, J.B. (Xinjiang Astron. Obs., Urumqi) ; Wang, J. (Bielefeld U.) ; Wang, L. (NAOC, Beijing) ; Witt, C.A. (West Virginia U.) ; Zhang, S. (Purple Mountain Observ.) ; Zhu, X.J. (Beijing Normal U.)
Publication	2022-01-27
Imprint	2022-01-11
Number of pages	15
Note	17 pages, 12 figures, accepted in MNRAS
In:	Mon. Not. R. Astron. Soc. 510 (2022) 4873
DOI	10.1093/mnras/stab3418 (publication)
Subject category	astro-ph.IM ; Astrophysics and Astronomy ; astro-ph.HE ; Astrophysics and Astronomy
Abstract	We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North America, Europe, and Australia. In our reference search for a power law strain spectrum of the form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence for a spectrally-similar low-frequency stochastic process of amplitude $A = 3.8^{+6.3}_{-2.5}\times10^{-15}$ and spectral index $\alpha = -0.5 \pm 0.5$, where the uncertainties represent 95% credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of $\alpha = -2/3$, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is $A = 2.8^{+1.2}_{-0.8}\times10^{-15}$. Nonetheless, no significant evidence of the Hellings-Downs correlations that would indicate a gravitational-wave origin was found. We also analyzed the constituent data from the individual pulsar timing arrays in a consistent way, and clearly demonstrate that the combined international data set is more sensitive. Furthermore, we demonstrate that this combined data set produces comparable constraints to recent single-array data sets which have more data than the constituent parts of the combination. Future international data releases will deliver increased sensitivity to gravitational wave radiation, and significantly increase the detection probability.
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