Physics of Tidal Disruptions

Johns Hopkins University, Baltimore MD

Investigators

Abstract

For about fifteen years, astrophysicists have known that galaxies generally house supermassive black holes (BHs) at their centers. Although usually detected only through their gravity, there is another method to reveal otherwise unobservable BHs: stellar tidal disruptions, which are the destruction of a star that happens to pass extremely close to such a BH. The exciting and innovative techniques already developed to tackle this situation will be extended and improved and will have significant impact across many fields that require numerical calculations. Over roughly the last decade, dozens of these Tidal Disruption Events have now been discovered from the luminous flare each one produces. This characteristic flare gradually decays over a span of weeks to months. Unfortunately, the old theory has trouble explaining the new data, and its assumptions must be questioned. Recent work has opened new ways of thinking about these events, but progress has been hampered by the extreme computational demands of conventional numerical simulation methods. The present team has built a new simulation infrastructure that overcomes these obstacles, and permits high-quality calculations incorporating full general relativity and three-dimensional magnetohydrodynamics. This tool enables three new avenues of research: (1) understanding the nature of both the accretion flow onto the black hole and the ejection of unbound debris after the star is torn apart; (2) exploring how black hole spin may shape the accretion flow and possibly support relativistic jets; and (3) providing quantitative predictions of the light curves and spectra produced. Societal benefits come from training a young scientist in the broadly applicable techniques of large-scale numerical simulation, expanding modern instructional methods in undergraduate physics education, and developing the innovative computing methodology for future public release.