Physics Colloquium: Mysterious quasi-periodic signals from centers of external galaxies

The Department of Physics is pleased to welcome Dr. Dheeraj “DJ” Pasham for an in-person colloquium presentation. DJ is a research scientist at MIT’s Kavli Institute for Astrophysics and Space Research. DJ is primarily an observer and uses multi-wavelength data (X-ray, optical, UV and Radio) to address many of the open questions about tidal disruption flares.

Abstract:

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 various flavors of quasi-periodic modulations that we have identified using multiwavelength studies of several classes of cosmic transients including stellar tidal distribution events, quasi-periodic eruptions from nuclei of external galaxies, and outbursts from active galactic nuclei. I will present the case of these quasi-periodic modulations as manifestations of EMRIs and will highlight the prospects they hold for the coming decade. I will also discuss–equally exciting–alternatives to explain the range of observed properties of these mysterious signals.

This is an in-person colloquium. If you are interested in attending virtually, please contact phyadmin@syr.edu for the Zoom link.