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Center for Nonlinear Studies |
Galactic nuclei are the most extreme stellar environments in the Universe. With orbital velocities in the hundreds or thousands of kilometers per second, stars and compact remnants inside the influence radii of supermassive black holes (SMBHs) easily reach densities numbering in the millions per cubic parsec. In these environments, frequent close encounters between different combinations of stars and compact objects produce powerful electromagnetic and gravitational wave (GW) transients. One notable such transient is a tidal disruption event (TDE), a luminous accretion-powered flare produced when an unlucky star is torn apart by a SMBH. Several dozen strong candidate TDEs have been observed so far, and after overviewing the basic theory of these events, I will focus on (i) open questions concerning TDE physics and (ii) ways in which general relativity is imprinted into TDE observables. In the second part of my talk, I will discuss the dynamical production of LIGO-band black hole mergers in galactic nuclei. Several theoretical mechanisms have been proposed to assemble stellar mass black holes into tight binaries, but I will pay special attention to the novel "AGN channel," in which black holes embedded in large-scale accretion disks are rapidly driven to merge via hydrodynamic torques.
Host: Roseanne Cheng