# Constraining gravitational wave propagation using pulsar timing array correlations

## TL;DR

This paper uses pulsar timing array data to test for subluminal gravitational wave modes, constraining the graviton mass and finding no evidence for certain GW correlation types.

## Contribution

It introduces a method to constrain graviton mass using PTA correlations and applies it to real data, providing new upper bounds.

## Key findings

- No evidence for tensor- or vector-induced GW correlations.
- Vector correlations are disfavored by the data.
- Upper bound on graviton mass is approximately 10^{-22} eV.

## 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, $m_{\rm g} \lesssim 10^{-22}$ eV, characteristic of the PTA GW energy scale.