An ASCA GIS spectrum of S5 0014+813 AT Z = 3.384

ASCA has detected the z = 3.384 quasar S5 0014+813 up to energies of 34 keV in the quasar rest frame using the two GIS instruments. The combined X-ray spectrum has a signal-to-noise ratio of over 50 σ and is consistent with a single power law of energy slope 0.63 +/- 0.03 over the 0.8-8 keV (observed) energy range. The spectrum is also well fitted with a simple thermal bremsstrahlung model of kT = 40 +/- 4 keV (in the quasar frame), which raises obvious possibilities for contributions to the diffuse X-ray background. A maximum solid angle of {OMEGA}_d_/2π = 0.4(90% confidence) can be placed on the strength of a Compton reflection component above the energy of the Fe K-edge. The Fe K 6.4 keV fluorescence line has a rest frame equivalent width <120 eV (90% confidence) at its redshifted energy of 1.46 keV. The weakness of these features differentiates this high- luminosity, high-redshift quasar from the majority of Seyfert galaxies using its X-ray spectrum alone. The GIS slope is consistent with the slope derived by the ROSAT PSPC. The normalization at 1 keV in the ASCA observation is, however, a factor 30%-40% higher than in the ROSAT observation, suggesting a significant increase in the 1 keV (observed) flux over the 31.5 months between the two observations (7.2 months, rest frame).