SuperTIGER instrument abundances of galactic cosmic rays for the charge interval 41 ⩽ Z ≤ 56

Abstract

We report preliminary elemental abundance results from the 55-day long-duration-balloon flight of SuperTIGER (Super Trans-Iron Galactic Element Recorder) during the 2012-2013 austral summer. SuperTIGER measured the relative abundances of Galactic cosmic-ray (GCR) nuclei with high statistical precision and well resolved individual element peaks from ₁₀Ne to ₄₀Zr. SuperTIGER also made exploratory measurements of the relative abundances up to ₅₆Ba. Although the statistics are low for elements heavier than ₄₀Zr, we present, for the first time, relative abundance measurements of charges Z = 41-56 with individual element resolution. GCR 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. In addition, injection into the GCR for both refractory and volatile elements appears to follow a charge dependence consistent with their grain sputtering cross sections. By extending the GCR measurement range past ₄₀Zr, we can begin to further constrain these models.

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