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The Question

(Submitted August 06, 1996)

I am a PhD student at the Observatory in Torino (Italy).

I would like to ask you if is it possible to have high-energy gamma emissions (that's to say up to 30 MeV) from some kind of dissections of nuclei? I know about Carbon and Oxygen at about 5-6 MeV and I know about the decay energy emission (e.g. aluminum and iron and others) not up to 10 MeV. Can one use EGRET or other similar high-energy satellites (e.g. in the future AMS) to study stellar production of some kind of nuclei (excited for example by the passage of a shock wave)?

The Answer

Thanks for your question about gamma-ray lines and satellite capabilities to study production of these nuclei. We've consulted with Dr. David Thompson (of the EGRET team here at NASA/Goddard) about your questions.

The highest energy gamma-ray line of which we are aware is one at about 20 MeV resulting from an exited state of tritium. Tritium is so unstable, however, that it is unlikely to be significant in any astrophysical situation. There are a few other lines between 10 and 20 MeV, but the vast majority of deexcitation lines, and all those which have been considered likely astrophysical candidates, have energies below 10 MeV.

EGRET does have some energy measurement capability at 20 MeV, but not with adequate resolution to see a narrow line. The same is likely to be true of AMS or GLAST. A far more promising avenue for the study of astrophysical lines is INTEGRAL, which has the high resolution and high sensitivity in the energy range of greatest interest.

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