Speaker: Prof. Maria Charisi (Washington State University, USA)

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Title: Multi-messenger astrophysics with pulsar timing arrays

Abstract: A Pulsar Timing Array (PTA) is a galactic-scale detector that relies on precision timing of milli-second pulsars. Recently, all major PTA collaborations have found evidence of a low-frequency gravitational wave background. The most likely origin of this background is a population of supermassive black hole binaries (SMBHBs) formed in galaxy mergers. I will present the exciting recent results from the North American Nanohertz Observatory for Gravitational waves (NANOGrav) collaboration, and their meaning for SMBHB evolution. I will also describe the next major milestone, which is likely the detection of an individual resolved binary. These systems, which should stand above the background, are also expected to be bright sources of electromagnetic emission, and can be detected as quasars with periodic variability. I will summarize the status of current electromagnetic searches, challenges in their detection and prospects for the future with the Rubin Observatory. Finally, I will discuss recent work which combines electromagnetic and gravitational-wave data and aims to deliver the first multi-messenger detection of a SMBHB.