http://arxiv.org/abs/1903.03117
Most of the stars are believed to be born in binaries or higher-multiplicity systems. The implications of the presence of a binary population in galactic nuclei have been under scrutiny only recently. Observations suggest that our Galactic Centre harbours at least a few binaries and a candidate binary S-star (S0-27). In this paper, we study the fate stellar binaries orbiting a supermassive black hole (SMBH) in its vicinity by means of $N$-body simulations, including tidal forces and Post-Newtonian terms. We focus on the Lidov-Kozai (LK) effect induced by the SMBH on massive binaries, which would lead to the formation of compact objects that later can merge via gravitational wave emission. We investigate how the properties of the merging binaries change with varying the SMBH mass, the slope of the initial mass function, the distributions of the binary orbital parameters and the efficiency in energy dissipation in dissipative tides. We find that the fraction of merging massive binary stars is in the range $\sim 5\%$–$20\%$ regardless of the details of the initial distributions of masses and orbital elements. For a Milky Way-like nucleus, we find a typical rate of $\Gamma\approx 1.4\times 10^{-7}$ yr$^{-1}$. The merger products of massive binaries can be rejuvenated blue-straggler stars, more massive than each of their original progenitors, and G2-like objects. Binary systems that survive the LK cycles can be source of X-rays and gravitational waves, observable with present and upcoming instruments.
G. Fragione
Mon, 11 Mar 19
38/78
Comments: 10 pages, 7 figures, 1 table
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