------------------------------------------------------------------------
 imbhgc_gcn.tex MNRAS, 384, 323-330, 2008
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%http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2966.2007.12699.x
%astro-ph/0711.1326

\documentclass[usenatbib]{mn2e}

\begin{document}

\title{Tracing intermediate-mass black holes in the Galactic Centre}

\author[U. L\"ockmann and H. Baumgardt]
{
   U. L\"ockmann$^{1}$\thanks{e-mail: uloeck@astro.uni-bonn.de (UL); 
holger@astro.uni-bonn.de (HB)},
   H. Baumgardt$^{1}$\footnotemark[1]\\
   %
   $^{1}$Argelander Institute for Astronomy, University of Bonn, Auf dem 
H\"ugel 71, 53121 Bonn,
   Germany\\
}

\label{firstpage}

\begin{abstract}
We have developed a new method for post-Newtonian, high-precision 
integration of stellar systems
containing a super-massive black hole (SMBH),
splitting the forces on a particle between a dominant central force and 
perturbations.
We used this method to perform fully collisional $N$-body simulations of
inspiralling intermediate-mass black holes (IMBHs)
in the centre of the Milky Way.
We considered stellar cusps of different power-law indices
and analysed the effects of IMBHs of different masses, all starting from 
circular orbits at an
initial distance of 0.1\,pc.

Our simulations show how IMBHs deplete the central cusp of stars,
leaving behind a flatter cusp with slope consistent with what has 
recently been observed.
If an additional IMBH spirals into such a flat cusp, it can take 50\,Myr 
or longer to merge with the central SMBH,
thus allowing for direct observation in the near future.
The final merger of the two black holes involves gravitational wave 
radiation which may be observable with planned gravitational wave detectors.

Furthermore, our simulations reveal detailed properties of the 
hyper-velocity stars (HVSs)
created, and how generations of HVSs can be used to trace IMBHs in the 
Galactic centre.
We find that significant rotation of HVSs (which would be evidence for 
an IMBH) can only be expected
among very fast stars ($v > 1000$\,km/s).
Also, the probability of creating a hyper-velocity binary star is found 
to be very small.

\end{abstract}



\begin{keywords}
Galaxy: centre -- methods: $N$-body simulations -- black hole physics -- 
stellar dynamics
\end{keywords}


\end{document}