The hard X-ray emission and44Ti emission of Cas A Original Research Article

We present an analysis of the BeppoSAX high X-ray energy spectrum of the supernova remnant Cassiopeia A with an observation time of 83 103 s. We measure a flux upper limit of 4.1 10−5 ph cm−2 s−1 (99.7% confidence) of the nuclear decay lines of44Ti at 68 keV and 78 keV that is lower and inconsistent with the flux of an accompanying line at 1157 keV measured by CGROʹs Comptel. However, if the underlying X-ray continuum is lower, because the spectrum is steepening, the actual44Ti may be higher and consistent with the Comptel result, although the measured flux of (2.9±1.0) 10−5 ph cm−2 s−1 under this assumption is still lower than the flux measured by Comptel.