The International Pulsar Timing Array second data release: Search for an isotropic gravitational wave background. Issue 4 (19th January 2022)

• Record Type: Journal Article
• Authors: Antoniadis, J; Arzoumanian, Z; Babak, S; Bailes, M; Bak Nielsen, A-S; Baker, P T; Bassa, C G; Bécsy, B; Berthereau, A; Bonetti, M; Brazier, A; Brook, P R; Burgay, M; Burke-Spolaor, S; Caballero, R N; Casey-Clyde, J A; Chalumeau, A; Champion, D J; Charisi, M; Chatterjee, S; Chen, S; Cognard, I; Cordes, J M; Cornish, N J; Crawford, F; Cromartie, H T; Crowter, K; Dai, S; DeCesar, M E; Demorest, P B; Desvignes, G; Dolch, T; Drachler, B; Falxa, M; Ferrara, E C; Fiore, W; Fonseca, E; Gair, J R; Garver-Daniels, N; Goncharov, B; Good, D C; Graikou, E; Guillemot, L; Guo, Y J; Hazboun, J S; Hobbs, G; Hu, H; Islo, K; Janssen, G H; Jennings, R J; Johnson, A D; Jones, M L; Kaiser, A R; Kaplan, D L; Karuppusamy, R; Keith, M J; Kelley, L Z; Kerr, M; Key, J S; Kramer, M; Lam, M T; Lamb, W G; Lazio, T J W; Lee, K J; Lentati, L; Liu, K; Luo, J; Lynch, R S; Lyne, A G; Madison, D R; Main, R A; Manchester, R N; McEwen, A; McKee, J W; McLaughlin, M A; Mickaliger, M B; Mingarelli, C M F; Ng, C; Nice, D J; Osłowski, S; Parthasarathy, A; Pennucci, T T; Perera, B B P; Perrodin, D; Petiteau, A; Pol, N S; Porayko, N K; Possenti, A; Ransom, S M; Ray, P S; Reardon, D J; Russell, C J; Samajdar, A; Sampson, L M; Sanidas, S; Sarkissian, J M; Schmitz, K; Schult, L; Sesana, A; Shaifullah, G; Shannon, R M; Shapiro-Albert, B J; Siemens, X; Simon, J; Smith, T L; Speri, L; Spiewak, R; Stairs, I H; Stappers, B W; Stinebring, D R; Swiggum, J K; Taylor, S R; Theureau, G; Tiburzi, C; Vallisneri, M; van der Wateren, E; Vecchio, A; Verbiest, J P W; Vigeland, S J; Wahl, H; Wang, J B; Wang, J; Wang, L; Witt, C A; Zhang, S; Zhu, X J;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 510:Issue 4(2022)
• Page Start: 4873
• Page End: 4887
• Publication Date: 2022-01-19
• Subjects: gravitational waves -- methods: data analysis -- pulsars: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab3418
• Languages: English
• ISSNs: 0035-8711

Abstract

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 $A = 3.8^{+6.3}_{-2.5}\times 10^{-15}$ and spectral index α = −0.5 ± 0.5, where the uncertainties represent 95 per cent credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of α = −2/3, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is $A = 2.8^{+1.2}_{-0.8}\times 10^{-15}$ . None the less, no significant evidence of the Hellings–Downs correlations that would indicate a gravitational-wave origin was found. We also analysed 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.