GRB and supernovae in the light of Swift

Some long gamma-ray bursts are connected with supernovae, such as GRB060218 with SN2006aj, recently discovered by Swift. In such GRB/SN, the prompt thermal and non-thermal, and the afterglow X-ray emission, as well as the early (t<1d) optical-UV emission, can all be explained by a model in which a radiation-mediated shock propagates through a compact progenitor star into a dense wind. The thermal X-rays would signal the shock break-out through the wind, and the non-thermal X-ray and γ-rays may be due, at least partly, to bulk Comptonization in the semi-relativistic SN ejecta. In fall-back collapsar scenarios, X-ray precursors may be associated with an initial proto-neutron star, followed by a subsequent black hole leading to the main burst.