Graduate Student Seminar with Wolfgang Zober on Galactic Cosmic Ray Astrophysics

In the past decade, recent multi messenger observations have established NS mergers as one of the sites of r-process nucleosynthesis. After this landmark discovery, the question has become, where is the primary site of r-process nucleosynthesis? Is it NS-NS mergers, supernovae and other core-collapse events, a mixture, or just some other process that contributes significantly to the heavy r-process budget of the universe. Our Galactic Cosmic Ray measurements up to 40Zr support a source acceleration model where supernovae in OB associations preferentially accelerate refractory elements that are more readily embedded in interstellar dust grains than volatiles. However, our preliminary measurements of the Z=41-56 range suggest the existence of an alternative GCR source or acceleration model for Z>40 elements. This talk will cover the use of CALET as a check on those measurements through Z=40 and how we aspire to go beyond Z=56 with the recently proposed TIGERISS mission, which, if selected, will be able to probe the relative contribution of r-process elements from 28Ni to 82Pb and aid in the search for signatures of different sources and further constrain sites of r-process nucleosynthesis.