StarTrack predictions of the stochastic gravitational-wave background from compact binary mergers. (arXiv:2008.04890v2 [astro-ph.CO] UPDATED)

<a href="http://arxiv.org/find/astro-ph/1/au:+Perigois_C/0/1/0/all/0/1">C. Périgois</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Belczynski_C/0/1/0/all/0/1">C. Belczynski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bulik_T/0/1/0/all/0/1">T. Bulik</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Regimbau_T/0/1/0/all/0/1">T. Regimbau</a>

We model the gravitational-wave background created by double compact objects

from isolated binary evolution across cosmic time using the

textbf{textit{StarTrack}} binary population code. We include Population I/II

stars as well as metal-free Population III stars. Merging and non-merging

double compact object binaries are taken into account. In order to model the

low frequency signal in the band of the space antenna LISA, we account for the

evolution of the redshift and the eccentricity. We find an energy density of

$Omega_{GW} sim 7.5 times 10^{-10}$ at the reference frequency of 25 Hz for

population I/II only, making the background detectable after $sim$5.5 years of

observation with the current generation of ground based detectors, such as

LIGO, Virgo and Kagra, operating at design sensitivity. Adding the contribution

from population III increases the energy density to $Omega_{GW} sim 1.4

times 10^{-8}$, and also modifies the shape of the spectrum which starts

deviating from the usual power law $Omega_{GW}(f) sim f^{2/3}$ after $sim

10$ Hz. The contribution from the population of non merging binaries, on the

other hand, is negligible, being orders of magnitude below. Finally, we observe

that the eccentricity has no impact in the frequency band of LISA or ground

based detectors.

We model the gravitational-wave background created by double compact objects

from isolated binary evolution across cosmic time using the

textbf{textit{StarTrack}} binary population code. We include Population I/II

stars as well as metal-free Population III stars. Merging and non-merging

double compact object binaries are taken into account. In order to model the

low frequency signal in the band of the space antenna LISA, we account for the

evolution of the redshift and the eccentricity. We find an energy density of

$Omega_{GW} sim 7.5 times 10^{-10}$ at the reference frequency of 25 Hz for

population I/II only, making the background detectable after $sim$5.5 years of

observation with the current generation of ground based detectors, such as

LIGO, Virgo and Kagra, operating at design sensitivity. Adding the contribution

from population III increases the energy density to $Omega_{GW} sim 1.4

times 10^{-8}$, and also modifies the shape of the spectrum which starts

deviating from the usual power law $Omega_{GW}(f) sim f^{2/3}$ after $sim

10$ Hz. The contribution from the population of non merging binaries, on the

other hand, is negligible, being orders of magnitude below. Finally, we observe

that the eccentricity has no impact in the frequency band of LISA or ground

based detectors.

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