COMPTEL observations of the quasars 3C 273 and 3C 279.


We report results from two COMPTEL observations, in June and October 1991, of the high galactic latitude region containing the quasars 3C 273 and 3C 279. The COMPTEL instrument, on board the Compton Gamma Ray Observatory, is sensitive over the energy range 0.75-30.0MeV. In June 1991 both quasars were detected, making them the first quasars observed at soft MeV energies, but during the October 1991 observation neither quasar was seen. Our data show that at MeV energies 3C 273 is variable on a time scale of months. However, we are unable to confirm the simultaneous, more rapid variability of 3C 279 seen above 100MeV by EGRET in June 1991. In the COMPTEL energy domain, the June spectra of the two quasars, differ significantly: 3C 279 had a harder spectrum than 3C 273. When the COMPTEL data are combined with contemporaneous data from other instruments 3C 273 exhibits a softening of its spectrum at high energies, with the change in slope occurring within the COMPTEL energy range near ~2MeV.



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Astronomy and Astrophysics


European Southern Observatory (ESO)

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