A search for the signature of microquasars in the cosmic ray iron spectrum measured by TIGER

Abstract

In a recent paper Heinz and Sunyaev suggest that relativistic jets observed in microquasars might result in narrow features in the energy spectra of heavy cosmic rays with ≈1 to ≈10 GeV/nuc. They further argue that such features might be observable if there has been one or more microquasars nearby within the last few million years. We report preliminary results of a search for evidence of such features using data from a 32-day balloon flight of the Trans-Iron Galactic Element Recorder (TIGER). Although this flight took place near solar maximum, calculations of the broadening effects of solar modulation indicate that a narrow feature of sufficient intensity should still be observable. An energy spectrum for iron with high statistical significance has been derived from ≈100,000 Fe events in the energy range from about 2.5 to 10 GeV/nuc. Although our preliminary results do not reveal any obvious features, we will discuss the possibility of observing such features with TIGER and other instruments.