Non-Gaussian Statistics of Nanohertz Stochastic Gravitational Waves

Xue, Xiao; Dai, Liang; Pan, Zhen

Preprint

PUBDB-2024-05893

Non-Gaussian Statistics of Nanohertz Stochastic Gravitational Waves

Xue, X. (Corresponding author)Extern*DESY* ; Pan, Z. ; Dai, L.

2024

[10.3204/PUBDB-2024-05893]

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Please use a persistent id in citations: doi:10.3204/PUBDB-2024-05893

Report No.: DESY-24-137; arXiv:2409.19516

Abstract: Recent detection of nHz stochastic gravitational wave background (SGWB) by multiple pulsar timing arrays (PTAs) has stimulated intensive discussions about its physical origin. In principle, either supermassive black hole binaries (SMBHBs) or processes in the early universe may be the sources. One key difference between the two lies in the statistics of the SGWB frequency power spectrum. In particular, the often assumed Gaussian random SGWB does not accurately describe the distribution of the collective SMBHB emission. In this work, we present a semi-analytical framework for calculating the non-Gaussian statistics of SGWB power expected from SMBHBs. We find that (a) wave interference between individual SMBHBs with indistinguishable observed frequencies and (b) the Poisson fluctuation of the source numbers, together shape the non-Gaussian statistics. Implementing the non-Gaussian statistics developed in this work, we investigate the sensitivity of current and future PTA datasets in distinguishing the origin of the SGWB through non-Gaussian information. Additionally, we find an interesting approximation of the non-Gaussian statistics, which has implications for accurately and practically treating non-Gaussianity in PTA Bayesian analyses.

Keyword(s): gravitational radiation, stochastic ; black hole, binary ; gravitational radiation, background ; statistics ; non-Gaussianity ; power spectrum ; fluctuation ; sensitivity ; interference ; Poisson ; Bayesian ; pulsar ; collective