Searching for Gravitational Waves from Cosmological Phase Transitions with the NANOGrav 12.5-Year Dataset

We search for a first-order phase transition gravitational wave signal in 45 pulsars from the NANOGrav 12.5-year dataset. We find that the data can be modeled in terms of a strong first order phase transition taking place at temperatures below the electroweak scale. However, we do not observe any strong preference for a phase-transition interpretation of the signal over the standard astrophysical interpretation in terms of supermassive black hole mergers; but we expect to gain additional discriminating power with future datasets, improving the signal to noise ratio and extending the sensitivity window to lower frequencies. An interesting open question is how well gravitational wave observatories could separate such signals.

Automated summary

The study explores a potential first-order phase transition gravitational wave signal, possibly occurring at temperatures below the electroweak scale, in 45 pulsars from the NANOGrav dataset. However, there is no strong preference for this phase-transition interpretation over the standard astrophysical explanation of supermassive black hole mergers. Future datasets are expected to improve discriminating power, enhance signal-to-noise ratio, and extend sensitivity to lower frequencies, offering a chance to better distinguish such signals.