INTEGRAL Picture Of the Month
May 2005

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INTEGRAL SPI observes the gamma-ray lines of interstellar 60Fe

The SPI instrument on board INTEGRAL has observed the 60Fe lines (at 1173 and 1333 keV) from the inner galaxy. The picture shows the combined 60Fe signal from the two lines. The line flux is 3.7 ± 1.1 x 10^5 cm^{-2} s^{-1} per line. The origin of the iron line is believed to be core-collapse supernovae which seed the interstellar medium with isotopes such as 60Fe. From other SPI measurements of the 26Al line the ratio 60Fe/26Al = 0.11 ±0.03 is derived, which is substantially smaller than predictions (0.40) for massive stars. This ratio supports the idea that there is an extra source of 26Al in addition to the core-collapse supernovae.

The results above are described in detail in a paper by Harris et al. ( A&A Letters, 2005, 433, 49)

Credits: M.J. Harris (CESR Toulouse) et al.
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