Pulsar timing array (PTA) collaborations in North America, Australia, and Europe, have been
exploiting the exquisite timing precision of millisecond pulsars over decades of observations …

Multi-messenger astrophysics, a long-anticipated extension to traditional multiwavelength
astronomy, has emerged over the past decade as a distinct discipline providing unique and …

Evidence for a low-frequency stochastic gravitational-wave background has recently been
reported based on analyses of pulsar timing array data. The most likely source of such a …

Observations indicate that nearly all galaxies contain supermassive black holes at their
centers. When galaxies merge, their component black holes form SMBH binaries (SMBHBs) …

Supermassive black hole binary systems form in galaxy mergers and reside in galactic
nuclei with large and poorly constrained concentrations of gas and stars. These systems …

Abstract We search NANOGrav's 12.5 yr data set for evidence of a gravitational-wave
background (GWB) with all the spatial correlations allowed by general metric theories of …

We calculate the properties, occurrence rates and detection prospects of individually
resolvable 'single sources' in the low-frequency gravitational wave (GW) spectrum. Our …

Pulsar timing array collaborations, such as the North American Nanohertz Observatory for
Gravitational Waves (NANOGrav), are seeking to detect nanohertz gravitational waves …

Supermassive black hole binaries (SMBHBs) should form frequently in galactic nuclei as a
result of galaxy mergers. At subparsec separations, binaries become strong sources of low …

The recent discovery of gravitational waves from merging black holes has generated interest
in primordial black holes as a possible component of dark matter. In this paper, we show that …