Scientific Seminars

How to Cook Pancakes with Massive Black Holes

Shiho Kobayashi
Astrophysics Research Institute, Liverpool John Moores University

2009-12-10    15.00    Merate - POE

I discuss two classes of extreme events reflecting the tidal disruption process around massive black holes. 1) Stars orbiting closely enough to a massive black hole could be tidally compressed into a transient pancake-shape configuration. Using hydrodynamical simulations, I show the formation of a strong shock within the stellar matter, and discuss its implications to X-ray and gravitational wave astronomy. 2) The leading models for the formation of hyper-velocity stars is the breakup of a binary as it approaches the massive black hole in the Galactic Center. The large mass ratio between the black hole and binary stars allows us to formulate the problem in the restricted parabolic three-body approximation. I show that the formulation and the behavior of the derived equations could be understood in the context of the stellar pancake mechanism. Contrary to previous claims, we show that, upon binary disruption, a lighter star in a binary does not remain preferentially bound to the black hole. In fact, it is ejected exactly in 50% of the cases. We provide the probability distribution for disruption of binaries and for the ejection energies.