GRBs and SNe

Andrew MacFadyen (IAS) gave a nice talk about collapsars—relativistic outflows from newly forming black holes punching through their massive stellar envelopes and appearing as gamma-ray bursts. He had some simulations which suggest that the relativistic jet can bore a hole through the envelope to make a channel for a clean (ie, not mass-loaded) jet. One piece of evidence for this general picture is the association of GRBs and SNe, which has gotten very good recently. In related news, he doubts that all massive stars go supernova, and thinks the supernova properties might depend strongly on metallicity and other factors. This is good news for those of us who are suspicious about using chemical abundances to trace formation histories.