The second data release from the European Pulsar Timing Array

🤖 Plain-English Summary

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). Further investigation of these issues is required for reliable astrophysical interpretations of this signal.

🔑 Key Findings

• 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.

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