An Update on the NANOGrav search for Gravitational Waves from SMBHBs

Dan Stinebring (Oberlin College)

August 29, 2019

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Abstract: Now that we are firmly in the era of gravitational wave (GW) detection, it is important to continue to detect sources across as wide a range of the GW spectrum as possible. Pulsar timing arrays are sensitive to gravitational waves with periods of a few weeks to ten years or more, the so-called nanohertz portion of the GW spectrum. The main sources in this part of the spectrum are expected to be supermassive black hole binaries (SMBHBs) with orbital separations less than a parsec. NANOGrav is the US-Canadian pulsar timing array collaboration. I will review the limits that NANOGrav has set on various GW signals in the nanohertz range, highlighting the rapidly increasing tension between those limits and predictions of galaxy mergers at redshifts of 1 or less. I will mention the role that CITA plays in pioneering efforts to understand scattering in the interstellar medium, work that is helping us to mitigate the effects of time-variable scattering delays in our pulsar timing data.