By performing general relativistic hydrodynamics simulations with an
    approximate neutrino-radiation transfer, the properties of ejecta in dynamical
    and post-merger phases are investigated for the cases in which the remnant
    massive neutron star collapses into a black hole in $\lesssim 20$ ms after the
    onset of the merger. The dynamical mass ejection is investigated in
    three-dimensional simulations. The post-merger mass ejection is investigated in
    two-dimensional axisymmetric simulations with viscosity using the
    three-dimensional post-merger systems as the initial conditions. We show that
    the typical neutron-richness of the dynamical ejecta is higher for the merger
    of more asymmetric binaries; hence, heavier $r$-process nuclei are dominantly
    synthesized. The post-merger ejecta are shown to have only a mild
    neutron-richness, which results in the production of lighter $r$-process
    nuclei, irrespective of binary mass ratios. Because of the larger disk mass,
    the post-merger ejecta mass is larger for more asymmetric binary mergers. Thus,
    the post-merger ejecta can compensate for the underproduced lighter $r$-process
    nuclei for asymmetric merger cases. As a result, by summing up both ejecta
    components, the solar residual $r$-process pattern is reproduced within the
    average deviation of a factor of three, irrespective of the binary mass ratio.
    Our result also indicates that the (about a factor of a few) light-to-heavy
    abundance scatter observed in $r$-process-enhanced stars can be attributed to
    variation in the binary mass ratio and total mass. Implications of our results
    associated with the mass distribution of compact neutron star binaries and the
    magnetar scenario of short gamma-ray bursts are discussed.

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