Stochastic Background from Coalescences of NS-NS Binaries

Abstract

In this work, numerical simulations were used to investigate the gravitational stochastic background produced by coalescences occurring up to $z \sim 5$ of double neutron star systems. The cosmic coalescence rate was derived from Monte Carlo methods using the probability distributions for forming a massive binary and to occur a coalescence in a given redshift. A truly continuous background is produced by events located only beyond the critical redshift $z_* = 0.23$. Events occurring in the redshift interval $0.027<z<0.23$ give origin to a "popcorn" noise, while those arising closer than $z = 0.027$ produce a shot noise. The gravitational density parameter $Ω_{gw}$ for the continuous background reaches a maximum around 670 Hz with an amplitude of $1.1\times 10^{-9}$, while the "popcorn" noise has an amplitude about one order of magnitude higher and the maximum occurs around a frequency of 1.2 kHz. The signal is below the sensitivity of the first generation of detectors but could be detectable by the future generation of ground based interferometers. Correlating two coincident advanced-LIGO detectors or two EGO interferometers, the expected S/N ratio are respectively 0.5 and 10.