1 Introduction

COMPTEL has demonstrated that the sky is rich in phenomena that can be studied at MeV energies. A variety of gamma-ray emitting objects are visible either in continuum or line emission. Among the continuum sources are spin-down pulsars, stellar black-hole candidates, supernova remnants, interstellar clouds, nuclei of active galaxies, gamma-ray bursters, and the Sun during solar flares. Line detections have been made in the light of the 1.809 MeV ²⁶Al line, the 1.157 MeV ⁴⁴Ti line, the 847 and 1238 keV ⁵⁶Co lines, and the neutron capture line at 2.223 MeV.

COMPTEL has also measured the diffuse interstellar and cosmic gamma radiation, whose properties are described elsewhere ([Strong et al. 1996]; Strong et al. 1999; [Bloemen et al. 1999a]; [Kappadath et al. 1996]; Weidens-pointner et al. [1999]). For the identification of galactic sources a modelling of the diffuse galactic emission is essential. Such a modelling at this time does not yet exist at the required degree of accuracy.

This paper is restricted to all those sources that have been definitely or marginally detected so far, and provides upper limits to the MeV flux from different types of objects. A second COMPTEL source catalogue will be produced after a detailed and accurate modelling of the diffuse interstellar emission has become possible.

The Compton Observatory was launched on April 5, 1991 by the Space Shuttle Atlantis. During Phase-I of the Compton Observatory Program, a full-sky survey - the first ever in gamma-ray astronomy - was performed. Phase-I ended on November 17, 1992. Observations during the subsequent phases of the program resulted in deeper exposures and complemented the survey. This source catalogue is mainly restricted to the results from the first five years of the mission (up to Phase IV/Cycle-5). In a few cases, more recent results have been added.