In this contribution we discuss the ^ { 44 } { } Ti nucleosynthesis \gamma -ray lines and their visibility with SIMBOL-X from simulations based on its expected sensitivity and spectro-imaging capabilities .
The ^ { 44 } { } Ti radioactive nucleus can provide invaluable information on the details of supernova explosions .
Its lifetime of \sim 85 yrs makes it the best indicator of the youth of these stellar explosions through its three \gamma -ray lines at 67.9 , 78.4 \mathrm { keV } and 1.157 \mathrm { MeV } .
We focus on the youngest Galactic supernova remnants , namely : Cassiopeia A , for which the location and Doppler-velocity estimates of the ^ { 44 } { } Ti-emitting regions in the remnant would offer for the first time a unique view of nucleosynthesis processes which occurred in the innermost layers of the supernova ; SN 1987A , in the Large Magellanic Cloud , whose progenitor is known , and for which the expected measurement of these lines would greatly constrain the stellar evolution models ; Tycho and Kepler SNRs for which ^ { 44 } { } Ti lines have never been detected so far .
The issue of the ” young , missing and hidden ” supernova remnants in the Galaxy will also be addressed using SIMBOL-X observations at the position of the ^ { 44 } { } Ti excesses that wide-field instruments like those onboard INTEGRAL and SWIFT /BAT should be able to reveal .