Presentation #109.02 in the session “Multi-Messenger Astrophysics (Session)”.
TIGERISS is an Ultra-Heavy Galactic Cosmic Ray (UHGCR) detector being proposed to the NASA Astrophysics Pioneers program capable of measuring the abundance relative to 26Fe of every element from 5B to 82Pb. It is an evolution of the TIGER and SuperTIGER long duration balloon instruments incorporating detector improvements out of the Heavy-Nuclei Explorer SMEX. TIGERISS will have a greatly improved capability to definitively identify UHGCR nuclei that has been demonstrated in component accelerator tests at CERN, including silicon strip detectors in place of scintillators. The geometry factor for TIGERISS is estimated to be from 1.1 to 1.7 m2 sr depending on the ISS attachment point, compared to 0.6 m2 sr for TIGER. Within one-year TIGERISS would observe statistics through 56Ba comparable to the current SuperTIGER data set. TIGERISS results will be cleaner, not requiring corrections for atmospheric interactions and scintillator saturation effects, and preliminary measurements to higher charges will test models for cosmic-ray origins and acceleration.
Multi messenger observations of a LIGO gravitational wave event have established neutron-star mergers (NSM) as one of the sites of r-process nucleosynthesis. TIGERISS will measure UHGCR nuclei resulting from s-process neutron-capture nucleosynthesis, as well as r-process in supernovae (SN) and NSM. SuperTIGER UHGCR measurements through 40Zr support a model of CR origins in OB Associations with preferential acceleration of refractory elements more likely found in dust grains than volatiles superposed on Z dependence from grain sputtering injection in SN shocks. More recent SuperTIGER results from 41Nb to 56Ba are inconsistent with the current model and require a difference in the acceleration mechanism and/or an additional r-process source. TIGERISS will probe the relative contribution of r-process elements to the cosmic rays from 28Ni to 82Pb and search for signatures of different sources.