BeppoSAX observations of the maser Seyfert 2 galaxy ESO 103-G35

We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO 103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra observed by BeppoSAX in 1996 O ctober and 1997 October yields a spectral index alpha (E) = 0.74 +/- 0.07 ( F-v proportional to v(-alphaE)), which is typical of Seyfert galaxies and c onsistent with earlier observations of this source. The strong, soft X-ray absorption has a column density N-H of 1.79 +/- 0.09 x 10(23) cm(-2), again consistent with earlier results. The best-fitting spectrum is that of a po wer law with a high-energy cutoff at 29 +/- 10 keV, a cold (E = 6.3 +/- 0.1 keV, rest frame), marginally resolved (sigma = 0.35 +/- 0.14 keV, FWHM sim ilar to 31 +/- 12 x 10(3) km s(-1)) Fe K alpha line with EW 290(-80)(+100) eV (1996), and a mildly ionized Fe K edge at 7.37(-0.21)(+0.15) keV, tau = 0.24(-0.09)(+0.06). The K alpha line and cold absorption are consistent wit h origin in an accretion disk/torus through which our line of sight passes at a radial distance of similar to 50 pc. The Fe K edge is mildly ionized, suggesting the presence of ionized gas, probably in the inner accretion dis k close to the central source or in a separate warm absorber. The data qual ity is too low to distinguish between these possibilities, but the edge-on geometry implied by the water maser emission favors the former. Comparison with earlier observations of ESO 103-G35 shows little or no change in spect ral parameters while the flux changes by factors of a few on timescales of a few months. The 2-10 keV flux decreased by a factor of similar to2.7 betw een 1996 October and 1997 October with no detectable change in the count ra te greater than 20 keV (i.e., the Phoswich Detector System data). Spectral fits to the combined data sets indicate either a significant hardening of t he spectrum (alpha (E) similar to 0.5) or an approximately constant or dela yed response reflection component. The high-energy cutoff (29 +/- 10 keV) i s lower than the typical similar to 300 keV values seen in Seyfert galaxies . A significant subset of similar sources would affect current models of th e active galactic nucleus contribution to the cosmic X-ray background which generally assume a high-energy cutoff of similar to 300 keV.