Insights into the Galactic Cosmic-ray Source from the TIGER Experiment

• Main Authors: Streitmatter, R. E., Barbier, L. M., Mitchell, J. W., Israel, M. H., deNolfo, G. A., Lodders, K., Christian, E. R., Link, Jason T., Geier, S., Rauch, B. F., Mewaldt,R. A., Waddington, C. J., Scott, L. M., Wiedenbeck, M. E., Schindler, S. M., Cummings, J. R., Stone, E. C., Binns, W. R.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2009
• Subjects: Astrophysics; Antarctic; Antarc*; Cris
• Online Access: http://hdl.handle.net/2060/20090033101

We report results from 50 days of data accumulated in two Antarctic flights of the Trans-Iron Galactic Element Recorder (TIGER). With a detector system composed of scintillators, Cherenkov detectors, and scintillating optical fibers, TIGER has a geometrical acceptance of 1.7 sq m sr and a charge resolution of 0.23 cu at Iron. TIGER has obtained abundance measurements of some of the rare galactic cosmic rays heavier than iron, including Zn, Ga, Ge, Se, and Sr, as well as the more abundant lighter elements (down to Si). The heavy elements have long been recognized as important probes of the nature of the galactic cosmic-ray source and accelerator. After accounting for fragmentation of cosmic-ray nuclei as they propagate through the Galaxy and the atmosphere above the detector system, the TIGER source abundances are consistent with a source that is a mixture of about 20% ejecta from massive stars and 80% interstellar medium with solar system composition. This result supports a model of cosmic-ray origin in OB associations previously inferred from ACE-CRIS data of more abundant lighter elements. These TIGER data also support a cosmic-ray acceleration model in which elements present in interstellar grains are accelerated preferentially compared with those found in interstellar gas.