Host: Dr. Matthew Liska

Title: Quasi-periodic Eruptions

Abstract: Quasi-Periodic Eruptions (QPEs) are a newly discovered type of recurring X-ray transient originating from supermassive black holes (SMBHs) in nearby, low-mass galaxy nuclei. They are thought to be the first observed counterparts to extreme mass-ratio inspirals (EMRIs), a long-anticipated gravitational wave source class detectable by future space-based interferometers (e.g. LISA). About a dozen QPEs are known, and in an unexpected twist, several of them have emerged from the nascent accretion disks formed by Tidal Disruption Events (TDEs). I will give an overview of the surprising discoveries, observational properties, and theoretical progress in QPEs since their discovery six years ago, including constraints on their emission mechanisms, prospects for probing EMRI orbital dynamics using QPE timings, and estimates of the QPE rate and their implication for EMRI formation. I will also briefly discuss ongoing work regarding the X-ray variability properties of TDEs as probes of their turbulent accretion flows, and electromagnetic study of evolutionary processes in ultracompact binary LISA sources, putting QPEs in the broader context of time-domain and multi-messenger astronomy.