Comparing Recent Pulsar Timing Array Results on the Nanohertz Stochastic Gravitational-wave Background
Gabriella Agazie, John Antoniadis, Akash Anumarlapudi, Anne M. Archibald, P. Arumugam, S. Arumugam, Z. Arzoumanian, Jacob Askew, S. Babak, Manjari Bagchi, M. Bailes, A.-S. Bak Nielsen, P. T. Baker, C. Bassa, Adarsh Bathula, B. Bécsy, A. Berthereau, N. D. R. Bhat, Laura Blecha, Matteo Bonetti, Elisa Bortolas, Adam Brazier, Paul R. Brook, M. Burgay, Sarah Burke-Spolaor, Rand Burnette, R. N. Caballero, A D Cameron, Robin Case, A. Chalumeau, D. J. Champion, S. Chanlaridis, Maria Charisi, Shami Chatterjee, Katerina Chatziioannou, B. D. Cheeseboro, Siyuan Chen, Zu-Cheng Chen, I. Cognard, Tyler Cohen, W. A. Coles, J. M. Cordes, Neil J. Cornish, F. Crawford, H. Thankful Cromartie, Kathryn Crowter, M. Curyło, Curt Cutler, Shi Dai, Subhajit Dandapat, Debabrata Deb, Megan E. DeCesar, Dallas DeGan, Paul B. Demorest, Hong Deng, S. Desai, G. Desvignes, Lankeswar Dey, N. Dhanda-Batra, Valentina Di Marco, Timothy Dolch, B. Drachler, C. Dwivedi, Justin A. Ellis, M. Falxa, Yi Feng, R. D. Ferdman, E. C. Ferrara, William Fiore, Emmanuel Fonseca, Alessia Franchini, Gabriel E. Freedman, J. R. Gair, N. Garver-Daniels, Peter A. Gentile, Kyle A. Gersbach, Joseph Glaser, Deborah C. Good, B. Goncharov, A. Gopakumar, E. Graikou, J.‐M. Grießmeier, L. Guillemot, Kayhan Gültekin, Y. J. Guo, Yashwant Gupta, Kathrin Grunthal, Jeffrey S. Hazboun, Shinnosuke Hisano, G. Hobbs, Sophie Hourihane, H. Hu, F. Iraci, Kristina Islo, David Izquierdo–Villalba, J. Jang, J. Jawor, G. H. Janssen, Ross J. Jennings, A. Jessner
Abstract
Abstract The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1 σ . The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we “extended” each PTA’s data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the Hellings–Downs correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA’s Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA.