Ultra-Heavy Galactic Cosmic Ray Abundances from the SuperTIGER Instrument: evidence for an OB association origin of GCR

We report Galactic Cosmic Ray (GCR) abundances of elements from $_{26}$Fe to $_{40}$Zr measured by the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument during 55 days of exposure on a long-duration balloon flight over Antarctica. SuperTIGER measures charge (Z) and energy (E) using a combination of three scintillator and two Cherenkov detectors, and employs a scintillating fiber hodoscope for event trajectory determination. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. We also derived GCR source abundances, which support a model of cosmic-ray origin in which the source material consists of a mixture of 19$^{+11}_{-6}$\% material from massive stars and $\sim$81\% normal interstellar medium (ISM) material with solar system abundances. The results also show a preferential acceleration, ordered by atomic mass (A), of refractory elements over volatile elements by a factor of $\sim$4. Both the refractory and volatile elements show a mass-dependent enhancement with similar mass dependence.