Vol. 544
In section 1. Letters

On the nature and detectability of Type Ib/c supernova progenitors

The progenitors of type Ibc supernovae have proven extremely difficult to detect. This difficulty has classically been attributed to the stars exploding as type Ibc supernovae being very low-mass optically faint He-rich stars produced in close binaries. This paper presents an interesting/attractive alternative explanation by demonstrating that the massive He-cores predicted by single massive-star models evolve into a very hot region of the Hertzsprung-Russell diagram (HRD) immediately before exploding. The visual-band bolometric corrections in this region of the HRD are high enough for the cores to have only faint optical emission in spite of the high total luminosity.