Optical and infrared observations of radioactive elements in supernovae

Abstract

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, ⁵⁶Ni, 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 ⁵⁶Ni than any other supernova to date. I will also discuss our ISO non-detection of [Fe II] 26 μm in SN 1987A, which can be used to estimate an upper limit on the mass of ejected radioactive ⁴⁴Ti.