Supernovae and gamma-ray bursts

Observational evidence indicates that the outflow of material in many, possibly even in all Supernovae, is not spherical. Here we review the evidence in Type Ic SNe associated with Gamma-Ray Bursts (GRB-SNe). These SNe are thought to originate in very massive stars. They are particularly suited to study the details of the collapse process because they are not enshrouded in a thick hydrogen envelope, exposing the inner carbon-oxygen core, near the site of collapse, and because of the link with GRBs. In the more massive stars (M approximate to 40M(circle dot)), observations may be interpreted to indicate that the SN explosion is driven by the mass inflow into the compact remnant, and that this remnant must be a Black Hole. This seems to be a necessary requirement for the SN also to generate a GRB. For less massive stars (M approximate to 20M(circle dot)), the remnant may be a neutron star and megnetic activity may be responsible for the energetic explosion and an X-ray Flash.