Galactic hum

Abstract

A number of earth's tremor spectral peaks show a persistent narrow bandwidth incompatible with any geophysical or instrumental origin. These peaks, located at frequencies lower than a few mHz, are in principle consistent with the earth strain waves induced by monochromatic gravitational waves. Exploring this hypothesis under the current cosmological constraints yields that the tremor peaks below 2 mHz are in apparently significant coincidence with the theoretical emission of two binary systems each consisting of a small main sequence star with mass $\sim 10^{-1} M_{\odot}$, captured by Sgr A* in a close orbit.