4 years ago

Secular Instabilities of Keplerian Stellar Discs around a Massive Black Hole.

S. Sridhar, Karamveer Kaur, Mher Kazandjian, Jihad Touma

We present idealized models of razor--thin, axisymmetric, Keplerian stellar discs around a massive black hole, and study non-axisymmetric secular instabilities in the absence of either counter-rotation or loss cones. These discs are prograde mono-energetic waterbags, whose phase space distribution functions are constant for orbits within a range of eccentricities (e) and zero outside this range. Waterbags which include circular orbits (polarcaps) have one stable linear edge-mode for each azimuthal wavenumber m. The m=1 mode always has positive pattern speed and, for polarcaps consisting of orbits with e < 0.9428, only the m=1 mode has positive pattern speed. Waterbags excluding circular orbits (bands) have two linear edge-modes for each m, which can be stable or unstable. We derive analytical expressions for the instability condition, pattern speeds, growth rates and normal mode structure. Narrow bands are unstable to modes with a wide range in m. Numerical simulations confirm linear theory and follow the non-linear evolution of instabilities. Long-time integration suggests that instabilities of different m grow, interact non-linearly and relax collisionlessly to a coarse-grained equilibrium with a wide range of e.

Publisher URL: http://arxiv.org/abs/1710.11340

DOI: arXiv:1710.11340v1

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.