We study the black hole formation and the neutrino signal from thegravitational collapse of a non-rotating massive star of 40 Msun. Adopting twodifferent sets of realistic equation of state (EOS) of dense matter, we performthe numerical simulations of general relativistic neutrino-radiationhydrodynamics under the spherical symmetry. We make comparisons of the corebounce, the shock propagation, the evolution of nascent proto-neutron star andthe resulting re-collapse to black hole to reveal the influence of EOS. We alsoexplore the influence of EOS on the neutrino emission during the evolutiontoward the black hole formation. We find that the speed of contraction of thenascent proto-neutron star, whose mass increases fast due to the intenseaccretion, is different depending on the EOS and the resulting profiles ofdensity and temperature differ significantly. The black hole formation occursat 0.6-1.3 sec after bounce when the proto-neutron star exceeds its maximummass, which is crucially determined by the EOS. We find that the averageenergies of neutrinos increase after bounce because of rapid temperatureincrease, but at different speeds depending on the EOS. The duration ofneutrino emission up to the black hole formation is found different accordingto the different timing of re-collapse. These characteristics of neutrinosignatures are distinguishable from those for ordinary proto-neutron stars insuccessful core-collapse supernovae. We discuss that a future detection ofneutrinos from black-hole-forming collapse will contribute to reveal the blackhole formation and to constrain the EOS at high density and temperature.
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