Constraining gravitational wave propagation using pulsar timing array correlations

Abstract

Pulsar timing arrays (PTA) are a promising probe to the cosmologically novel nanohertz gravitational wave (GW) regime through the stochastic GW background. In this work, we consider subluminal GW modes as a possible source of correlations in a PTA, utilizing the public code PTAfast and the 12.5 years correlations data by NANOGrav, which we hypothesize are sourced by GWs. Our results show no evidence in support of tensor- or vector-induced GW correlations in the data, and that vector correlations are disfavored. This places an upper bound to the graviton mass, $m_{\mathrm{g}}\lesssim 10^{-22}$ eV, characteristic of the PTA GW energy scale.

6 pages + refs, 3 figures, v2: discussion improved, to appear in PRD Letters, our codes https://github.com/reggiebernardo/PTAfast/tree/main

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