The cosmic evolution of the neutron star merger ( NSM ) rate can be deduced from the observed cosmic star formation rate .
This allows to estimate the rate expected in the horizon of the gravitational wave detectors advanced Virgo and ad LIGO and to compare those rates with independent predictions .
In this context , the rapid neutron-capture process , or r-process , can be used as a constraint assuming NSM is the main astrophysical site for this nucleosynthetic process .
We compute the early cosmic evolution of a typical r-process element , Europium .
Eu yields from NSM are taken from recent nucleosynthesis calculations .
The same approach allows to compute the cosmic rate of Core Collapse SuperNovae ( CCSN ) and the associated evolution of Eu .

We find that the bulk of Eu observations at { [ Fe / H ] } > -2.5 can be rather well fitted by either CCSN or NSM scenarios .
However , at lower metallicity , the early Eu cosmic evolution favors NSM as the main astrophysical site for the r-process .
A comparison between our calculations and spectroscopic observations at very low metallicities allows us to constrain the coalescence timescale in the NSM scenario to \sim 0.1–0.2 Gyr .
These values are in agreement with the coalescence timescales of some observed binary pulsars .
Finally , the cosmic evolution of Eu is used to put constraints on i ) the NSM rate , ii ) the merger rate in the horizon of the gravitational wave detectors advanced Virgo/ad LIGO , as well as iii ) the expected rate of electromagnetic counterparts to mergers ( ” kilonovae ” ) in large near-infrared surveys .