2014MNRAS.438.3119Y

We investigate the possibility of a superluminous Type Ic core-collapse supernovae (SNe) producing a large amount of 56Ni. Very massive stars with a main-sequence mass larger than 100M_☉ and a metallicity 0.001 < Z ≲ 0.004 are expected to explode as superluminous Type Ic SNe. Stars with ∼ 110-150M_☉ and Z ≲ 0.001 would explode as Type Ic pulsational pair-instability SNe if the whole H and He layer has been lost by the mass-loss during pulsational pair instability. We evaluate the total ejecta mass and the yields of 56Ni, O and Si in core-collapse SNe evolved from very massive stars. We adopt 43.1 and 61.1M_☉ WO stars with Z = 0.004 as SN progenitors expected to explode as Type Ic core-collapse SNe. These progenitors have masses of 110 and 250M_☉ at the zero-age main sequence. Spherical explosions with an explosion energy larger than 2x10⁵²erg produce more than 3.5M_☉56Ni, enough to reproduce the light curve of SN 2007bi. Asphericity of the explosion affects the total ejecta mass as well as the yields of 56Ni, O and Si. Aspherical explosions of the 110 and 250M_☉ models reproduce the 56Ni yield of SN 2007bi. These explosions will also show large velocity dispersion. An aspherical core-collapse SN evolved from a very massive star is a possibility of the explosion of SN 2007bi.