Paper: astro-ph/0507133
Date: Wed, 6 Jul 2005 17:35:52 GMT (12kb)

Title: Binary Encounters With Supermassive Black Holes: Zero-Eccentricity LISA
Events

Authors: M. Coleman Miller (Univ. of Maryland), Marc Freitag (Northwestern),
Douglas P. Hamilton (Univ. of Maryland), and Vanessa M. Lauburg (Univ. of
Maryland)
Comments: 12 pages, submitted to ApJ Letters
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Current simulations of the rate at which stellar-mass compact objects merge
with supermassive black holes (called extreme mass ratio inspirals, or EMRIs)
focus on two-body capture by emission of gravitational radiation. The
gravitational wave signal of such events will likely involve a significant
eccentricity in the sensitivity range of the Laser Interferometer Space Antenna
(LISA). We show that tidal separation of stellar-mass compact object binaries
by supermassive black holes will instead produce events whose eccentricity is
nearly zero in the LISA band. Compared to two-body capture events, tidal
separations have a high cross section and result in orbits that have a large
pericenter and small apocenter. Therefore, the rate of interactions per binary
is high and the resulting inspirals are relatively unaffected by subsequent
perturbations by other stars. Depending on the fraction of compact objects that
are in binaries within a few parsecs of the center, the rate of
low-eccentricity LISA events could be comparable to or larger than the rate of
high-eccentricity events. This relative rate depends strongly on properties of
compact binaries that are difficult to characterize using other observational
techniques. Therefore, LISA observations of the eccentricity distribution will
provide information, integrated over the galaxies with observed EMRIs, about
compact binaries in galactic nuclei.

\\ ( http://arXiv.org/abs/astro-ph/0507133 , 12kb)