ASCA Observations of the Seyfert 2 Galaxy NGC 7582: an Obscured and Scattered View of the Hidden Nucleus

ASCA observations of the Seyfert 2 galaxy NGC 7582 revealed that it was highly variable on the timescale of ~ 2*E(4) s in the hard X-ray band (2--10 keV), while the soft X-ray (0.5--2 keV) flux remained constant during the observations. The normalized variability amplitude in the hard X-ray band was sigma_RMS ~ 0.3, which is the same level as that of Seyfert 1 galaxies of the same luminosity ~ 3 times 10(42) erg s(-1) (2--10 keV). The spectral analysis suggests that this object is seen through an obscuring torus with the thickness of N_H ~ 1.0times 10(23) cm(-2) . The hard X-rays are an absorbed direct continuum from a hidden Seyfert 1 nucleus, while the soft X-rays are dominated by the scattered central continuum from an extended spatial region. We have an obscured/absorbed and a scattered view of this source as expected from the unification model for Seyfert galaxies. More interestingly, the inferred column density increased by ~ 4*E(22) cm(-2) from 1994 to 1996, suggesting a ``patchy'' torus structure, namely the torus might be composed of many individual clouds. The observed iron-line feature near 6.4 keV with the equivalent width of 170 eV is also consistent with the picture of the transmission of nuclear X-ray continuum through a non-uniform torus.