On the origin of He 0107-5240, the most iron-deficient star presently known

We show that the "puzzling" chemical composition observed in the extremely metal-poor star HE 0107 - 5240 may be naturally explained by the concurrent pollution of at least two supernovae. In the simplest possible model, a supernova of quite low mass (similar to 15 M-.) underwent a " normal" explosion and ejected similar to0.06 M-.. of while Ni-56 a second one was massive enough (similar to35 M-.) to experience a strong fallback that locked in a compact remnant all the carbon-oxygen core. In a more general scenario, the pristine gas clouds were polluted by one or more supernovae of relatively low mass (less than similar to25 M-.). The successive explosion of a quite massive star experiencing an extended fallback would have largely raised the abundances of the light elements in its close neighborhood.