IS THE X-RAY-SPECTRUM OF THE SEYFERT-2 GALAXY NGC-5252 INTRINSICALLY FLAT

The first X-ray observation of the Seyfert 2 galaxy NGC 5252 is report ed. ASCA Astro-D collected approximately 4000 photons per detector, en ough to perform an accurate spectral analysis of this source. The lumi nosity of NGC 5252 is L(x)(0.7-10 keV) similar or equal to 2.6 x 10(43 ) ergs s(-1), typical of a Seyfert 1 galaxy. A simple description of t he spectrum with a single power law is ruled out by the SIS data, whic h shows a strong soft excess at E less than or similar to 1.2 keV. The spectrum is best fitted by models assuming either partial covering of the central source or scattering of the X-ray continuum. The best-fit partial covering model results in a flat (Gamma similar or equal to 1 .45 +/- 0.2) power-law continuum emitted by a source almost completely covered (at similar to 94%-97%) by neutral matter [N-H similar or equ al to (4.3 +/- 0.6) x 10(22) cm(-2)]. The detected iron line is remark ably weaker (EW similar or equal to 90 +/- 60 eV) than normally found from Seyfert 2 galaxies. In an effort to interpret the observed hat sp ectrum with an intrinsically steep power law as predicted by unified m odels, we also included in the models neutral reflection, ionized abso rption (warm absorber), and nonuniform cold absorption (dual-absorber) . We find that the observed flat continuum and weakness of the iron li ne pose a problem for neutral reflection models, whatever the assumed geometry is. The use of an ionized absorber (scattering + warm-absorbe r model) instead of a neutral absorber seems unjustified with the pres ent data. The ''dual-absorber'' model, representing nonuniform (densit y) absorption along the line of sight, may provide an alternative expl anation for the flatness of the spectrum, with no constraints on the F e K emission line. Another plausible interpretation of the present dat a is that the X-ray spectrum of NGC 5252 is truly intrinsically flat. Its strong similarities with the well-known Seyfert 1.5 galaxy NGC 415 1 are briefly discussed.