We report the detection of the ^ { 44 } Sc nuclear decay lines at 67.9 keV and 78.4 keV associated with the nuclear decay of ^ { 44 } Ti in Cassiopeia A .
The line emission was observed by the PDS instrument on board BeppoSAX , which recently observed the supernova remnant for over 500 ks .
The detection of the line emission with a flux of ( 2.1 \pm 0.7 ) 10 ^ { -5 } { ph / cm ^ { 2 } / s } in each line ( 90 % confidence ) is at the 5 \sigma significance level , if we can assume that the 12-300 keV continuum is adequately represented by a single power law .
However , as the nature of the continuum is not clear we investigate various other possibilities .
A more conservative estimate of the line flux is made by assuming that a power law continuum is at least a good approximation to the continuum emission for a narrower 30-100 keV energy range .
With this limitation the measured line flux is ( 1.9 \pm 0.9 ) 10 ^ { -5 } { ph / cm ^ { 2 } / s } , with the detection still at the 3.4 \sigma significance level .
We suggest that together with the CGRO-COMPTEL measurement of the ^ { 44 } Ca line at 1157 keV of ( 3.3 \pm 0.6 ) 10 ^ { -5 } { ph / cm ^ { 2 } / s } a flux for all three lines of ( 2.5 \pm 1.0 ) 10 ^ { -5 } { ph / cm ^ { 2 } / s } for Cas A can be adopted .
This implies an initial ^ { 44 } Ti mass of ( 0.8 - 2.5 ) 10 ^ { -4 } M _ { \sun } .