Elemental and Isotopic Composition Measurements of Ultra-Heavy Galactic Cosmic Rays from SuperTIGER and ACE/CRIS
Abstract
We report on measurements of the elemental abundances of ultra-heavy cosmic rays (UHCR) by the SuperTIGER (Trans-Iron Galactic Element Recorder) and Advanced Composition Explorer (ACE) CRIS instruments, and isotopic abundances of UHCR from ACE/CRIS. The ST instrument flew on high-altitude balloons over Antarctica in 2012-2013 (55 day flight) and again in 2019-2020 (32 day flight). The CRIS instrument was launched in August 1997, and continues to collect data after 22 years in orbit. In the two flights of ST we collected $\sim$7000 nuclei with Z=30 or greater and on ACE/CRIS we collected $\sim$1100 nuclei with Z=30 or greater. The ST data have enabled us to measure elemental abundances for Z=26-56. The ACE/CRIS data has enabled us to measure the cosmic ray element abundances of Z=29-40 nuclei and isotopic abundances of Z=31-34 for the first time and to greatly improve earlier published measurements for Z=29-30. The energy ranges for ST and CRIS are >0.8GeV/nuc and $\sim$150-600 MeV/nuc respectively. In this paper we report elemental abundances for Z=29-40 from ST and CRIS and preliminary isotopic abundances for Z=29-34 from CRIS. For elemental abundances, we find that the ST and CRIS data are in generally good agreement for most elements and are consistent with the source material being a mix of normal interstellar medium material (with Solar System composition) with ejecta and wind outflow from massive stars. The source abundances of the refractory elements show an enhancement of $\sim$x4 relative to the volatiles and also a mass dependence. The isotopic composition of Z=29-33 nuclei is generally consistent with Solar System abundances. However, the Z=34 isotope distribution appears to differ significantly from that in the Solar System. This research is supported by NASA Grant Numbers 80NSSC18K0223 & NNX15AC15G.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1332B