We investigate the gravitational wave ( GW ) signal generated by a population of double neutron-star binaries ( DNS ) with eccentric orbits caused by kicks during supernova collapse and binary evolution .
The DNS population of a standard Milky-Way type galaxy has been studied as a function of star formation history , initial mass function ( IMF ) and metallicity and of the binary-star common-envelope ejection process .
The model provides birth rates , merger rates and total numbers of DNS as a function of time .
The GW signal produced by this population has been computed and expressed in terms of a hypothetical space GW detector ( eLISA ) by calculating the number of discrete GW signals at different confidence levels , where ‘ signal ’ refers to detectable GW strain in a given frequency-resolution element .
In terms of the parameter space explored , the number of DNS-originating GW signals is greatest in regions of recent star formation , and is significantly increased if metallicity is reduced from 0.02 to 0.001 , consistent with .
Increasing the IMF power-law index ( from –2.5 to –1.5 ) increases the number of GW signals by a large factor .
This number is also much higher for models where the common-envelope ejection is treated using the \alpha - mechanism ( energy conservation ) than when using the \gamma - mechanism ( angular-momentum conservation ) .
We have estimated the total number of detectable DNS GW signals from the Galaxy by combining contributions from thin disc , thick disc , bulge and halo .
The most probable numbers for an eLISA-type experiment are 0 - 1600 signals per year at S/N \geqslant 1 , 0 - 900 signals per year at S/N \geqslant 3 , and 0 - 570 at S/N \geqslant 5 , coming from about 0 - 65 , 0 - 60 and 0 - 50 resolved DNS respectively .