Editors: Pau Amaro-Seoane & Bernard Schutz
The last GW Note is a Special Issues on eLISA/NGO

## Fast coalescence of massive black hole binaries from mergers of galactic nuclei: implications for low-frequency gravitational-wave astrophysics

arXiv:1102.4855

by Preto, Miguel and Berentzen, Ingo and Berczik, Peter and Spurzem, Rainer
6 pages, 4 figures, 1 table. Submitted to ApJL

We investigate a purely stellar dynamical solution to the Final Parsec Problem. Galactic nuclei resulting from major mergers are not spherical, but show some degree of triaxiality. With $latex N$-body simulations, we show that massive black hole binaries (MBHB) hosted by them will continuously interact with stars on centrophilic orbits and will thus inspiral—in much less than a Hubble time—down to separations at which gravitational wave (GW) emission is strong enough to drive them to coalescence. Such coalescences will be important sources of GWs for future space-borne detectors such as the {\it Laser Interferometer Space Antenna} (LISA). Based on our results, we expect that LISA will see between $latex \sim 10$ to $latex \sim {\rm few} \times 10^2$ such events every year, depending on the particular MBH seed model as obtained in recent studies of merger trees of galaxy and MBH co-evolution. Orbital eccentricities in the LISA band will be clearly distinguishable from zero with $latex e \gtrsim 0.001-0.01$.

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