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Astron. Astrophys. 338, L75-L78 (1998)

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Letter to the Editor

Diffuse galactic gamma rays, cosmic-ray nucleons and antiprotons

I.V. Moskalenko 1, 2, A.W. Strong 1 and O. Reimer 1

1 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
2 Institute for Nuclear Physics, M.V. Lomonosov Moscow State University, 119 899 Moscow, Russia

Received 31 July 1998 / Accepted 1 September 1998

Abstract

The excess of continuum [FORMULA]-ray emission from the Galaxy above 1 GeV is an unsolved puzzle. It may indicate that the interstellar nucleon or electron spectra are harder than local direct measurements, as could be the case if a local source of cosmic rays were to dominate the nearby flux. It is however difficult to distinguish between the two cases. Cosmic-ray secondary antiprotons provide a way to resolve this issue.

We have made a calculation of the cosmic-ray secondary antiproton spectrum in our model, which computes self-consistently propagation of primary and secondary nucleons, and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. Our study shows that accurate measurements of the antiproton flux, especially at high energies, could provide a diagnostic of the interstellar nucleon spectrum allowing us to test the hard nucleon spectrum hypothesis. Present antiproton data above 3 GeV indicate that it can already be excluded at the few [FORMULA] level.

Key words: diffusion – elementary particles – cosmic rays – ISM: general – Galaxy: general – gamma rays: theory

Send offprint requests to: A.W. Strong

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© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998
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