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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany

Preprint 03/96

Constraints on the 3-30 MeV emission of Seyfert galaxies

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

(1)Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany
(2)Universitäts-Sternwarte, Geismarlandstr. 11, 37083 Göttingen, Germany
(3)Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany

accepted by Astronomy & Astrophysics

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 gamma-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: active ; Gamma rays: observations

Paper (45k gzip'ed Postscript including figures)

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