The Hunt for Nanohertz Gravitational Waves by Dr. Xavier Siemens
Supermassive black hole binaries, and possibly other sources, generate gravitational waves in the nanohertz part of the spectrum. For over a decade and a half the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank Telescope, until recently the Arecibo Observatory, and the Very Large Array to observe millisecond pulsars. Our goal is to directly detect nanohertz gravitational waves, which cause small correlated perturbations to the times of arrival of radio pulses from millisecond pulsars. We currently monitor over 70 millisecond pulsars with sub-microsecond precision and weekly to monthly cadences. I will present an overview of our work and summarize the results of our most recent searches for gravitational-waves.