AN IRAS-SELECTED SEYFERT-2 GALAXY IRAS-18325-5926 - THE X-RAY SOURCE AND NUCLEAR OBSCURATION

We report x-ray and optical spectroscopic observations of an IRAS-selected Seyfert 2 galaxy IRAS 18325-5926. The first x-ray observation of this object was made using the Ginga LAG. The x-ray source is found to be highly variable on time scales of 10(3)-10(4) s, similar to those of Seyfert 1 nuclei. The x-ray spectrum is well described by power-law continuum with a photon-index Gamma similar or equal to 2.2 modified by photoelectric absorption intrinsic to the source with N-H similar or equal to 1.4x10(22) cm(-2) and a broad (sigma approximate to 0.6 keV) iron K line. The absorption corrected x-ray luminosity in the 2-10 keV band is L(X)=5.4x10(43)h(50)(-2) ergs s(-1). We obtained new optical spectra in red and blue bands, which show the strong emission lines of typical Seyfert 2s with a heavy reddening (A(V)=3.5 mag). A blue asymmetry is obvious in some strong emission Lines and we can resolve narrow (FWHM similar or equal to 450 kms(-1)) and slightly blueshifted (similar or equal to 160 km s(-1)) broad (FWHM similar or equal to 1200 km s(-1)) components. The optical classification of Seyfert 2s can be explained in terms of nuclear obscuration which may occur in the form of a ''global'' covering rather than in the form of a torus inferred from the unified model, since the extinction derived from optical and x-ray data are comparable. This fact suggests that the hypothesis in which the classification between Seyfert 1's and 2's depends on the orientation is not complete, and a global obscuration is likely to dominate the dusty IRAS galaxies with Seyfert 2 characteristics. (C) 1995 American Astronomical Society.