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Astron. Astrophys. 319, 397-400 (1997)

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Constraints on the 3-30 MeV emission of Seyfert galaxies

M. Maisack 1, K. Mannheim 2 and W. Collmar 3

1 Astronomisches Institut der Universität Tübingen, D-72076 Tübingen, Germany
2 Universitäts-Sternwarte, Geismarlandstr. 11, D-37083 Göttingen, Germany
3 Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany

Received 19 June 1996 / Accepted 9 August 1996

Abstract

Seyfert galaxies have not been detected by COMPTEL on the Compton Gamma Ray Observatory (CGRO) in the energy range 0.75-3 MeV, placing upper limits on their emission which are more than an order of magnitude below previously reported detections. Here, we extend our previous work to the energy range 3-30 MeV. Again, we find no evidence for emission from a cumulative sample of X-ray bright Seyfert galaxies. We use the recent results on the extragalactic background at MeV energies to constrain the possible emission of these sources and their contribution to the cosmic extragalactic background (CXB). The lack of [FORMULA] -rays from Seyfert galaxies strongly argues against hadronic cascades as the underlying radiation mechanism and, consequently, against recent claims that Seyferts might produce a high-energy neutrino background with an energy flux similar to that of the CXB.

Key words: galaxies: Seyfert – gamma rays: observations

Send offprint requests to: maisack@astro.uni-tuebingen.de

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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