Theoretical Physics Colloquium: Stellar Destruction near Supermassive Black Holes

27 Oct 2023
Seminars and colloquia
Lindemann Lecture Theatre
Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU

Itai Linial (Columbia)

Seminar series
Theoretical physics colloquia
Knowledge of physics?
Yes, knowledge of physics required
For more information contact


Centers of galaxies are fertile environments for a variety of dynamical processes, owing to the high density of stars and the presence of a central Supermassive Black Hole (SMBH). Fluctuations in the background potential resulting from two-body scatterings, as well as the dissipative nature of orbits in General Relativity through the emission of Gravitational Waves (GWs), shape the (quasi) steady-state distribution of orbits these systems settle to. I will introduce two main channels of stellar destruction caused by interaction with the central SMBH: Stars may be deflected onto a nearly radial trajectory where they are ripped apart by the SMBH’s tidal field, producing a luminous flare powered by the rapid fallback of stellar debris (known as Tidal Disruption Event, TDE), or alternatively, they may inspiral towards the SMBH on a nearly circular orbit until they begin to gradually shed their mass over many orbits (Extreme Mass Ratio Inspiral, EMRI). I will discuss the possible connection between these phenomena and a newly discovered class of repeating X-ray flares occurring in galactic nuclei, known as Quasi-Periodic Eruptions (QPEs). I will present a theoretical model for explaining the observations, involving a stellar EMRI interacting with the accretion flow produced by a recent TDE in the same galactic center. Finally, I will conclude by discussing the potential of QPEs and other repeating transients in galactic nuclei in testing our theoretical understanding of SMBHs and their environments - including measurements of their masses and spins, probing the nature of the accretion flow that forms around them, and constraining the dynamical processes that govern their engulfing stellar clusters.