Quasi-periodic Modulations following Nuclear Outbursts from Galaxies

Extreme Mass Ratio Inspirals (EMRIs) are binaries containing a massive black hole (≳a few hundred 1000 solar masses, Msol) and an orbiting smaller object (0.1-100 Msol). They are expected to be one of the primary sources of gravitational waves with space-based gravitational wave detectors that will start operating in the next decade. The identification of electromagnetic counterparts of these gravitational wave emitters would transform our understanding of supermassive black hole growth, probe dark energy and put fundamental constraints on gravity. I will present the discoveries of quasi periodic modulations from extragalactic nuclear outbursts. These signals could result from EMRIs formed during stellar tidal disruptions events (TDEs). Consequently, they could potentially be a new channel to study EMRIs as the next generation optical sky surveys are expected to discover hundreds to thousands of TDEs.