Pulsar Timing Arrays CHIME in on Gravitational Waves

The success of gravitational wave observations of stellar mass black hole mergers and neutron star mergers has proven that observational gravitational wave astronomy has an important part to play in coming years. However, ground-based laser interferometers can access only a limited portion of the gravitational wave spectrum. Low-frequency gravitational waves, such as those from supermassive black hole binaries, require different observational strategies.

One such strategy is high-precision pulsar timing arrays (PTAs). PTAs observe sets of millisecond pulsars, generating high-precision, long-term timing solutions. Gravitational wave signals from supermassive black hole binaries will appear in these timing solutions as correlated timing fluctuations with a unique angular signature. Unlike signals from stellar mass compact binary coalescences, these gravitational wave signals will be visible on approximately decade timescales; they are expected to appear gradually and grow over time.

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is one such PTA, primarily using data from the Green Bank Telescope and the Arecibo Observatory. The most recent NANOGrav results strongly suggest a stochastic common-spectrum process, which may prove to be an early indicator of a gravitational wave signal.

In this talk, I will provide an introduction to pulsar timing arrays, discuss the recent NANOGrav results, and look forward to the emerging contributions of CHIME/Pulsar in pulsar timing array science.