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Pair creation supernovae (PCSN) are thought to be produced from very massivelow metallicity stars. The spectacularly bright SN 2006gy does show signaturesexpected from PCSNe. Here, we investigate the metallicity threshold below whichPCSN can form and estimate their occurrence rate. We perform stellar evolutioncalculations for stars of 150$\mso$ and 250$\mso$ of low metallicity(Z$_{\odot}$/5 and Z$_{\odot}$/20), and analyze their mass loss rates. We findthat the bifurcation between quasi-chemically homogeneous evolution for fastrotation and conventional evolution for slower rotation, which has been foundearlier for massive low metallicity stars, persists in the mass rangeconsidered here. Consequently, there are two separate PCSN progenitor types:(I) Fast rotators produce PCSNe from very massive Wolf-Rayet stars, and (II)Slower rotators that generate PCSNe in hydrogen-rich massive yellowhypergiants. We find that hydrogen-rich PCSNe could occur at metallicities ashigh as Z$_{\odot}$/3, which -- assuming standard IMFs are still valid toestimate their birth rates -- results in a rate of about one PCSN per 1000supernovae in the local universe, and one PCSN per 100 supernovae at a redshiftof $z=5$. PCSNe from WC-type Wolf-Rayet stars are restricted to much lowermetallicity.

Pair creation supernovae at low and high redshift