Half-Life of44Tias a Probe for Supernova Models

Recent measurements of galactic radioactivity with the Compton Gamma Ray Observatory reported ${}^{44}\mathrm{Ti}$ activity from the supernova remnant Cassiopeia A. The absolute amount of ${}^{44}\mathrm{Ti}$ provides a stringent test for current supernova models. The main uncertainty is presently the half-life of ${}^{44}\mathrm{Ti}$. We report a new measurement of the half-life of ${}^{44}\mathrm{Ti}$ applying a novel technique using a mixed radioactive ion beam containing ${}^{44}\mathrm{Ti}$ as well as ${}^{22}\mathrm{Na}$ ions. This method allows the reliable determination of the half-life of ${}^{44}\mathrm{Ti}$ with high accuracy, $t_{1/2}=(60.3\pm 1.3)\mathrm{yr}$. The ${}^{44}\mathrm{Ti}$ abundance determined for Cassiopeia A with this half-life agrees with theoretical predictions within the observational uncertainties.