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 com
pare 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 high iron abundance 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 to constrain the coalescence timescale in the NSM scenario to about 0.1 to 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 the NSM rate, the merger rate in the horizon of the gravitational wave detectors advanced Virgo/ad LIGO, as well as the expected rate of electromagnetic counterparts to mergers (kilonovae) in large near-infrared surveys.
Primordial or Big Bang nucleosynthesis (BBN) is one of the three strong evidences for the Big- Bang model together with the expansion of the Universe and the Cosmic Microwave Background radiation. In this study, we improve the standard BBN calculatio
ns taking into account new nuclear physics analyses and we enlarge the nuclear network until Sodium. This is, in particular, important to evaluate the primitive value of CNO mass fraction that could affect Population III stellar evolution. For the first time we list the complete network of more than 400 reactions with references to the origin of the rates, including approx 270 reaction rates calculated using the TALYS code. Together with the cosmological light elements, we calculate the primordial Beryllium, Boron, Carbon, Nitrogen and Oxygen nuclei. We performed a sensitivity study to identify the important reactions for CNO, 9Be and Boron nucleosynthesis. We reevaluated those important reaction rates using experimental data and/or theoretical evaluations. The results are compared with precedent calculations: a primordial Beryllium abundance increase by a factor of 4 compared to its previous evaluation, but we note a stability for B/H and for the CNO/H abundance ratio that remains close to its previous value of 0.7 times 10-15. On the other hand, the extension of the nuclear network has not changed the 7Li value, so its abundance is still 3-4 times greater than its observed spectroscopic value.
