Radioactivity of the Key Isotope 44Ti in SN 1987A

We investigate radioactivity from the decay sequence of ⁴⁴Ti in a young supernova remnant SN 1987A. We perform Monte-Carlo simulations of degradation of the nuclear lines to explain a late-time bolometric luminosity which is estimated from optical and near-infrared observation at 3600 days after the explosion. Assuming the distance to LMC in between 45.5 and 52.1 kpc, we have obtained the initial ⁴⁴Ti mass of (0.82 - 2.3) × 10^-4Msolar within the current uncertainty of the physical quantities. The resulting fluxes of γ- and hard X-rays emerged from the ⁴⁴Ti decay are estimated and compared with the line sensitivity of the INTEGRAL/SPI on board and that of NeXT X-ray satellite planned to be launched in 2010. The effect of ⁴⁴Ti ionization on the estimated fluxes is briefly remarked.