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

Abstract

We investigate radioactivity from the decay sequence of 44Ti in young supernova remnants (SNRs), Cassiopeia A (Cas A) and SN 1987A. It is shown by a linear analysis that ionization of 44Ti, a pure electron capture decay isotope, affects the radioactivity contradistinctively in these two SNRs: Ionization of 44Ti 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 44Ti mass of (0.82-2.3) X 10^{-4} M_solar from our Monte-Carlo simulations. The resulting fluxes of gamma and hard X-rays emerged from the 44Ti decay are given for the current and future experiments.