We report the detection of both the 67.9 and 78.4 \mathrm { keV } ^ { 44 } { } Sc \gamma -ray lines in Cassiopeia A with the INTEGRAL IBIS/ISGRI instrument .
Besides the robustness provided by spectro-imaging observations , the main improvements compared to previous measurements are a clear separation of the two ^ { 44 } { } Sc lines together with an improved significance of the detection of the hard X-ray continuum up to 100 \mathrm { keV } .
These allow us to refine the determination of the ^ { 44 } { } Ti yield and to constrain the nature of the nonthermal continuum emission .
By combining COMPTEL , BeppoSAX /PDS and ISGRI measurements , we find a line flux of ( 2.5 \pm 0.3 ) \times 10 ^ { -5 } cm ^ { -2 } s ^ { -1 } leading to a synthesized ^ { 44 } { } Ti mass of 1.6 ^ { +0.6 } _ { -0.3 } \times 10 ^ { -4 } M _ { \odot } .
This high value suggests that Cas A is peculiar in comparison to other young supernova remnants , from which so far no line emission from ^ { 44 } { } Ti decay has been unambiguously detected .