Limits on MeV Emission from Active Galaxies Measured with COMPTEL
J.G. Stacy
S.C. Kappadath
W. Collmar, V. Scho\"nfelder, H. Steinle, A. Strong
H. Bloemen, J.J. Blom, W. Hermsen
J.M. Ryan
O.R. Williams
Abstract
We provide cumulative flux limits in the COMPTEL energy range for a
large sample of high-energy active galactic nuclei (AGN) of general
interest. In particular, we present the cumulative two-sigma upper
limits to the time-averaged MeV-emission measured with COMPTEL from
AGN and other unidentified gamma-ray sources detected at high Galactic
latitudes (\mid b \mid > 10°). These limits were
derived using composite COMPTEL all-sky maximum-likelihood maps for
the 4.5-year period covering Phases 1 through 4 of the CGRO mission
(1991-1995). The composite all-sky maps were produced from
standard-processing COMPTEL datasets for individual CGRO viewing
periods, in four standard energy bins spanning the sensitive range of
COMPTEL (0.75-1, 1-3, 3-10, and 10-30 MeV). We describe the
data-processing procedure, and compare it to related methods for
obtaining all-sky maximum likelihood maps using COMPTEL data. From
these maps we have extracted statistical likelihoods, significances of
potential source detections, and associated fluxes, errors, or upper
limits, for an extensive list of target objects. In the choice of
candidate objects, emphasis was placed on known or suspected gamma-ray
sources, particularly those detected in neighboring energy bands to
COMPTEL by the CGRO/EGRET and OSSE instruments. Finally, we assess
the implications of our limits on the possible contribution of AGN to
the diffuse gamma-ray background measured by COMPTEL in the MeV
regime.
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On 16 Jul 1999, 09:19.