Jerome NovakB Peres; M Oertel30 min

Phase transition to hyperons in proto-neutron stars

Immediately after its birth, the hot proto-neutron star accretes matter from the progenitor massive star and may collapse to a black hole. This is an event where extremely high temperatures and densities are reached; it is then expected that additional particles to nucleons and electrons shall appear. Hyperons are among the first ones expected. We present numerical simulations of the collapse of massive stars to proto-neutron star and finally black holes, with an equation of state allowing for the presence of $\Lambda$ hyperons. A feature of this equation of state is that its cold and beta-equilibrium version allows for neutrons stars with almost two solar masses, marginally compatible with recent observations. Spherically symmetric simulations, under some conditions, show the effect of a phase transition to hyperonic matter before the appearance of the black hole. We show axisymmetric simulations, too, where this phase transition is smoothed, but where gravitational waves show clear imprint of the presence of hyperons.