NEUTRINO-DRIVEN WINDS IN THE AFTERMATH OF A NEUTRON STAR MERGER: NUCLEOSYNTHESIS AND ELECTROMAGNETIC TRANSIENTS

Abstract

We present a comprehensive nucleosynthesis study of the neutrino-driven wind\nin the aftermath of a binary neutron star merger. Our focus is the initial\nremnant phase when a massive central neutron star is present. Using tracers\nfrom a recent hydrodynamical simulation, we determine total masses and\nintegrated abundances to characterize the composition of unbound matter. We\nfind that the nucleosynthetic yields depend sensitively on both the life time\nof the massive neutron star and the polar angle. Matter in excess of up to $9\n\\cdot 10^{-3} M_\\odot$ becomes unbound until $\\sim 200~{\\rm ms}$. Due to\nelectron fractions of $Y_{\\rm e} \\approx 0.2 - 0.4$ mainly nuclei with mass\nnumbers $A < 130$ are synthesized, complementing the yields from the earlier\ndynamic ejecta. Mixing scenarios with these two types of ejecta can explain the\nabundance pattern in r-process enriched metal-poor stars. Additionally, we\ncalculate heating rates for the decay of the freshly produced radioactive\nisotopes. The resulting light curve peaks in the blue band after about $4~{\\rm\nh}$. Furthermore, high opacities due to heavy r-process nuclei in the dynamic\nejecta lead to a second peak in the infrared after $3-4~{\\rm d}$.\n