Eric Coughlin from the University of California, Berkeley, will be the featured speaker at an upcoming Department of Physics and Astronomy colloquium. His talk is titled, "Stars Destroyed by Binary Supermassive Black Holes: A Numerical and Statistical Study."
When a star gets too close to a supermassive black hole — a gravitational behemoth that resides at the center of nearly every galaxy — the tidal force of the black hole overwhelms the self-gravity of the star. The star is subsequently tidally shredded and stretched into a stream of debris that, at later times, returns to the black hole, forms an accretion disk, and temporarily lights up the galactic center. These "tidal disruption events"' are unique probes of the centers of galaxies, giving us the opportunity to discern properties of quiescent black holes that are otherwise difficult to constrain observationally. Coughlin will describe recent work that investigates how a binary companion to the disrupting black hole alters both the tidal disruption process and the subsequent evolution of the tidally-disrupted debris. In particular, he will show that a supermassive black hole binary generates chaotic, three-body interactions that affect the pre-disruption orbit of the star, thereby providing a small enhancement to the tidal disruption rate. The post-disruption hydrodynamics of the disrupted debris are also modified considerably by the presence of the binary companion, leading to complex accretion morphologies and rates that vary over a range of spatial and temporal scales. These results have implications for current and upcoming wide-field surveys, which are predicted to discover hundreds to thousands of tidal disruption events over the next decade.