Collapse of rotating massive stars leading to black hole formation and energetic supernovae

Abstract

We explore a possible scenario of the explosion as a result of core collapses of rotating massive stars that leave a black hole by performing a radiation-viscous-hydrodynamics simulation in numerical relativity. We take moderately and rapidly rotating compact pre-collapse stellar models derived in stellar evolution calculations as the initial conditions. We find that the viscous heating in the disk formed around the central black hole powers an outflow. For rapidly rotating models, the explosion energy is $\gtrsim 3\times10^{51}$ erg, which is comparable to or larger than that of typical stripped-envelope supernovae, indicating that a fraction of such supernovae may be explosions powered by black-hole accretion disks. The explosion energy is still increasing at the end of the simulations with a rate of $>10^{50}$ erg/s, and thus, it may reach $\sim10^{52}$ erg. The nucleosynthesis calculation shows that the mass of $^{56}$Ni amounts to $\gtrsim 0.1M_\odot$, which, together with the high explosion energy, satisfies the required amount for broad-lined type Ic supernovae. The moderately rotating models predict small ejecta mass of order $0.1M_\odot$ and explosion energy of $\lesssim 10^{51}$ erg. Due to the small ejecta mass, these models may predict a short-timescale transient with the rise time 3$-$5 d. It can lead to a bright ($\sim10^{44}$ erg/s) transient like superluminous supernovae in the presence of dense massive circum-stellar medium. Irrespective of the models, the lowest value of the electron fraction of the ejecta is $\gtrsim 0.4$, and thus, the synthesis of heavy $r$-process elements is not found in our calculation.