Limits to the Cas A ${}^{44}$Ti Line Flux and Constraints on the Ejecta Energy and the Compact Source

R. E. Rothschild, R. E. Lingenfelter

Two long observations of Cas A supernova remnant were made by the \emph{Rossi X-ray Timing Explorer} in 1996 and 1997 to search for hard X-ray line emission at 67.9 and 78.4 keV fr…