Optical and Infrared Observations of Radioactive Elements in Supernovae
  At late phases the powering of supernova light curves is often provided by the decay of radioactive elements synthesized in the explosions. This is unambiguously revealed when the light curve decline follows the half life time of the decaying elements, and the bolometric luminosity then directly provides the mass of ejected radioactive material. I will focus on the best observed element, Nickel-56, and demonstrate that different supernovae eject different amounts of this element. SN 1994W ejected very small amounts of nickel, possibly caused by black hole formation. SN 1998bw may instead have ejected more Nickel-56 than any other supernova to date.   I will also discuss our ISO non-detection of [Fe II] 26 micron in SN 1987A, which can be used to estimate an upper limit on the mass of ejected radioactive Titanium-44. 
Jesper Sollerman