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Issue A&A
Volume 433, Number 3, April III 2005
Page(s) L49 - L52
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200500093



A&A 433, L49-L52 (2005)
DOI: 10.1051/0004-6361:200500093

Letter

Detection of $\mathsf{\gamma}$-ray lines from interstellar $\mathsf{^{60}}$Fe by the high resolution spectrometer SPI

M. J. Harris1, J. Knödlseder1, P. Jean1, E. Cisana2, R. Diehl3, G. G. Lichti3, J.-P. Roques1, S. Schanne4 and G. Weidenspointner1

1  Centre d'Étude Spatiale des Rayonnements, BP 4346, 31028 Toulouse Cedex 4, France
    e-mail: Mike.Harris@cesr.fr
2  IASF, via E. Bassini 15, 20133 Milano, Italy
3  Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany
4  DSM/DAPNIA/SAp, CEA Saclay, 91191 Gif-sur-Yvette, France

(Received 1 February 2005 / Accepted 23 February 2005 )

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 $\gamma$-rays emitted when they $\beta$-decay. Here we report the detection of the 60Fe decay lines at 1173 keV and 1333 keV with fluxes 3.7 $\pm$ 1.1 $\times$ $10^{-5}~\gamma~\hbox{cm}^{-2}~\hbox{s}^{-1}$ 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 $\pm$ 0.03. This supports the hypothesis that there is an extra source of 26Al in addition to CCSN.


Key words: ISM: abundances -- nucleosynthesis -- gamma-rays: observations




© ESO 2005

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