Radio follow-up of gravitational wave events

Tara Murphy (University of Sydney)

January 20, 2020

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Abstract: August 17th 2017 was a breakthrough for astrophysics. For the first time gravitational waves were detected from a binary neutron star merger (GW170817), and in the subsequent hours, days and weeks, an unprecedented electromagnetic follow-up campaign resulted in detections across all wavebands from gamma-rays through to radio. This event has led to new results on a wide range of topics: from heavy element production in the Universe, to independent measurements of the Hubble Constant, to the origin of short gamma-ray bursts. After 16 days of intensive monitoring, radio emission was detected by the Jansky Very Large Array (JVLA), and confirmed by our team with the Australia Telescope Compact Array. This was the first radio emission to be associated with gravitational wave events, and unambiguously associated with a binary neutron star merger. The radio emission we expected to see was a late-time afterglow, detectable months to years after the event as the shock travels out into the interstellar medium. However, what we detected was an entirely different phenomenon, most likely a cocoon of ejecta material breaking out from the explosion and interacting with the interstellar medium. With only one event observed, we currently have no way of knowing whether this is atypical, or the first of a new, intriguing, class of transient radio source. I will present our latest results from radio monitoring of GW170817 and our plans and recent results from radio follow-up of gravitational wave events in LIGO O3 and beyond.