44Ti radioactivity in young supernova remnants:: Cas A and SN 1987A

We investigate radioactivity from the decay sequence of Ti-44 in young supernova remnants (SNRs), Cassiopeia A (Cas A) and SN 1987A. It is shown by a linear analysis that ionization of Ti-44, a pure electron capture decay isotope, affects the radioactivity contradistinctively in these two SNRs: Ionization of Ti-44 to H-like and He-like states enhances its present radioactivity in Cas A, while such high-ionization decreases its radioactivity in SN 1987A. We briefly discuss the enhancement factor of the present radioactivity of Cas A considering microscopic (atomic/nuclear) physics combined with a hydrodynamical SNR evolution model. For SN 1987A, we have obtained the initial Ti-44 mass of (0.82-2.3)x10(-4) M-circle dot from our Monte-Carlo simulations. The resulting fluxes of gamma and hard X-rays emerged from the Ti-44 decay are given for the current and future experiments. (C) 2003 Elsevier B.V. All rights reserved.