ESA Science & Technology - SPI observations of the diffuse ⁶⁰Fe emission in the Galaxy

Publication date: 01 May 2007

Authors: Wang, W. et al.

Journal: to appear in A&A
arXiv:0704.3895v1 [astro-ph]
Year: 2007

Gamma-ray line emission from radioactive decay of ⁶⁰Fe provides constraints on nucleosynthesis in massive stars and supernovae. The spectrometer SPI on board INTEGRAL has accumulated nearly three years of data on gamma-ray emission from the Galactic plane. We have analyzed these data with suitable instrumental-background models and sky distributions to produce high-resolution spectra of Galactic emission. We detect the gamma-ray lines from ⁶⁰Fe decay at 1173 and 1333 keV, obtaining an improvement over our earlier measurement of both lines with now 4.9 sigma significance for the combination of the two lines. The average flux per line is (4.4 +- 0.9) x 10^-5 ph cm^-2 s^-1 rad^-1 for the inner Galaxy region. Deriving the Galactic ²⁶Al gamma-ray line flux with using the same set of observations and analysis method, we determine the flux ratio of ⁶⁰Fe/²⁶Al gamma-rays as 0.148 +- 0.06. The current theoretical predictions are still consistent with our result.