Title: Astrophysics with the NANOGrav Pulsar Timing Array
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration is working towards the detection and study of low-frequency gravitational waves (GWs) using an array of rapidly rotating, highly stable radio pulsars distributed across the galaxy. Each pulsar emits a radio beam that passes our line of sight and is observed as regular, pulsed emission. We measure the times of arrival of pulses and compare with a model that includes: the rotational motion of the pulsar, orbital motions, and interstellar propagation delays; random timing noise from pulsars themselves and from the interstellar medium; and a correlated GW signal. Therefore, pulsar timing array observations provide a rich data set to look at a wide variety of multi-messenger astrophysical phenomena. I will highlight areas of work being done by the NANOGrav collaboration, including the astrophysical constraints we have placed so far on the dynamics of supermassive black hole binaries at the centers of merging galaxies. I will briefly highlights the synergistic science obtained while we work to build our detector, such as the detection of the most massive neutron star known to date and the observation of an interstellar plasma lens along the line of sight toward one of our most precise pulsars.