Detection of γ-ray lines from interstellar 60Fe by the high resolution spectrometer SPI
Knödlseder, J.; Schanne, S.; Diehl, R.; Jean, P.; Lichti, G. G.; Weidenspointner, G.; Roques, J. -P.; Harris, M. J.; Cisana, E.
France, Italy, Germany
Abstract
It is believed that core-collapse supernovae (CCSN), occurring at a rate ~once per century, have seeded the interstellar medium with long-lived radioisotopes such as 60Fe (half-life 1.5 Myr), which can be detected by the γ-rays emitted when they β-decay. Here we report the detection of the 60Fe decay lines at 1173 keV and 1333 keV with fluxes 3.7 ± 1.1 × 10-5~γ~cm-2~s-1 per line, in spectra taken by the SPI spectrometer on board INTEGRAL during its first year. The same analysis applied to the 1809 keV line of 26Al yielded a line flux ratio 60Fe/26Al = 0.11 ± 0.03. This supports the hypothesis that there is an extra source of 26Al in addition to CCSN.