Probing the metastability of a protoneutron star with hyperons in a core-collapse supernova

The role of Λ hyperons is investigated in the dynamical collapse of a nonrotating massive star to a black hole using a one-dimensional general-relativistic (gr1d) code. The dynamical formation and evolution of a protoneutron star (PNS) to a black hole is followed using various progenitor models, adopting a hyperonic equation of state (EoS) generated by Shen et al. [Shen, Toki, Oyamatsu, and Sumiyoshi, Astrophys. J., Suppl. Ser. 197, 20 (2011)]. The results are compared with those of a nuclear EoS by Shen et al. [Shen, Toki, Oyamatsu, and Sumiyoshi, Nucl. Phys. A 637, 435 (1998)] to understand the role of Λ hyperons in the core-collapse supernova. The neutrino signals that may be used as a probe for core collapse is also discussed. Further, an exotic EoS may support a cold neutron star with a maximum mass much lower than that of a PNS. In this regard, the metastability of a PNS in the presence of Λ hyperons is studied in the long-time evolution of the progenitors, relevant to supernova SN1987A.