⁴⁰Ca(α,γ)⁴⁴Ti and the production of ⁴⁴Ti in supernovae

The nuclide Ti-44 is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based gamma-ray telescopes. The main production of Ti-44 takes place in the alpha-rich freeze-out phase deep inside the supernova. The key reactions governing the Ti-44 abundance have been identified in an earlier sensitivity study. Using the recoil mass spectrometer DRAGON at the TRIUMF-ISAC facility in Vancouver, Canada, we measured the main production reaction Ca-40(alpha,gamma)Ti-44, resulting in an increased reaction rate compared to the rate derived from previous prompt gamma-ray studies, which is commonly used in supernova models. The uncertainty of the Ti-44 production is now dominated by the rate of reactions with short-lived nuclides around Ti-44, namely V-45(p,gamma)Cr-46, Ti-44(alpha, p)V-47 and Ti-44(alpha,gamma)Cr-48. The sensitivity of these reactions on the Ti-44 production has been revisited.