We have obtained the average 1–500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT , Ginga , HEAO-1 , and GRO OSSE .
The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE , confirming results from an earlier Ginga /OSSE sample .
The average spectrum is well-fitted by a power-law X-ray continuum with an energy spectral index of \alpha \simeq 0.9 moderately absorbed by an ionized medium and with a Compton reflection component .
A high-energy cutoff ( or a break ) in the the power-law component at a few hundred keV or more is required by the data .
We also show that the corresponding average spectrum from HEAO-1 A1 and A4 is fully compatible with that obtained from EXOSAT , Ginga and OSSE .
These results confirm that the apparent discrepancy between the results of Ginga ( with \alpha \simeq 0.9 ) and the previous results of EXOSAT and HEAO-1 ( with \alpha \simeq 0.7 ) is indeed due to ionized absorption and Compton reflection first taken into account for Ginga but not for the previous missions .
Also , our results confirm that the Seyfert-1 spectra are on average cut off in \gamma -rays at energies of at least a few hundred keV , not at \sim 40 keV ( as suggested earlier by OSSE data alone ) .
The average spectrum is compatible with emission from either an optically-thin relativistic thermal plasma in a disk corona , or with a nonthermal plasma with a power-law injection of relativistic electrons .