Stefano

The final fate of massive stars is not well explored and depending on the stellar mass may have very much different outputs, ranging from very energetic explosions (e.g. GRB-SNe) to direct collapse on black-holes with very weak or not explosion at all (Heger, Woosley, & Baraffe, 2005).
Here I present the case of SN 1996al. I describe the physical properties of this luminous supernova in the framework of a very weak explosion (kinetic energy of sim 1.6 times 10^{50}$ erg), where the bolometric luminosity is sustained by the conversion of the kinetic energy into radiation thanks to the interaction between a low mass ($sim 1.15$ M$_{odot}$, 87% of which is Helium, the remaining is Hydrogen) symmetric ejecta with an highly asymmetric circum-stellar material. The detection of H$_{alpha}$~emission in pre-explosion archive images suggests that the progenitor of SN 1996al was most likely a massive star ($sim25$ M$_{odot} ZAMS) that had lost a large fraction of its hydrogen envelope before explosion, and was hence embedded in a H-rich cocoon. The low-mass ejecta and modest kinetic energy of the explosion are then explained with massive fallback of material into the compact remnant, a $7-8,M_{odot}$ black hole. Finally, I will try to place this particularly interesting SN in the framework of the SNIIn zoo.