Constraining the gravitational wave energy density of the Universe in the Range 0.1 Hz to 1 Hz using the Apollo Seismic Array

Abstract

In this paper, we describe an analysis of Apollo era lunar seismic data that places an upper limit on an isotropic stochastic gravitational-wave background integrated over a year in the frequency range 0.1\,Hz -- 1\,Hz. We find that because the Moon's ambient noise background is much quieter than that of the Earth, significant improvements over an Earth based analysis were made. We find an upper limit of $\Omega_{\rm GW}<1.2\times 10^{5}$, which is three orders of magnitude smaller than a similar analysis of a global network of broadband seismometers on Earth and the best limits in this band to date. We also discuss the benefits of a potential Earth-Moon correlation search and compute the time-dependent overlap reduction function required for such an analysis. For this search, we find an upper limit an order of magnitude larger than the Moon-Moon search.