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The Astrophysical Journal


The American Astronomical Society


Cas A, the youngest known supernova remnant in the Galaxy and a strong radio and Xray source, was observed by OSSE July 16 - August 6, 1992. Its close distance (¸ 3 kpc) and its young age (¸ 300 yrs) make Cas A the best candidate among known supernova remnants for detecting 44 Ti fl-ray lines. We find no evidence of emission at 67.9 keV, 78.4 keV, or 1.157 MeV, the three strongest 44 Ti decay lines. From simultaneous fits to the three lines our 99% confidence upper limit to the flux in each line is 5.5Theta10 Gamma5 fl cm Gamma2 s Gamma1 . We also report upper limits for the 4.44 MeV 12 C nuclear deexcitation line, which could be produced by interactions of accelerated particles in the supernova remnant, and for the hard X-ray continuum.


Additional author: M.P. Ulmer, Northwestern University