The eccentricity distribution of compact binaries
  The current gravitational wave detectors have reached their operational
sensitivity and are nearing detection of compact object binaries. In the coming
years, we expect that the Advanced LIGO/VIRGO will start taking data. At the
same time, there are plans for third generation ground-based detectors such as
the Einstein Telescope, and space detectors such as DECIGO. We discuss the
eccentricity distribution of inspiral compact object binaries during they
inspiral phase. We analyze the expected distributions of eccentricities at
three frequencies that are characteristic of three future detectors: Advanced
LIGO/VIRGO (30 Hz), Einstein Telescope (3 Hz), and DECIGO (0.3 Hz). We use the
StarTrack binary population code to investigate the properties of the
population of compact binaries in formation. We evolve their orbits until the
point that they enter a given detector sensitivity window and analyze the
eccentricity distribution at that time. We find that the eccentricities of
BH-BH and BH-NS binaries are quite small when entering the Advanced LIGO/VIRGO
detector window for all considered models of binary evolution. Even in the case
of the DECIGO detector, the typical eccentricities of BH-BH binaries are below
10^{-4}, and the BH-NS eccentricities are smaller than 10^{-3}. Some fraction
of NS-NS binaries may have significant eccentricities. Within the range of
considered models, we found that a fraction of between 0.2% and 2% NS-NS
binaries will have an eccentricity above 0.01 for the Advanced LIGO/VIRGO
detectors. For the ET detector, this fraction is between 0.4% and 4%, and for
the DECIGO detector it lies between 2% and 27%.
