Hard X-Ray Emission from a Type 2 Seyfert Galaxy (NGC 1068)

EXOSAT observations of the type 2 Seyfert galaxy NGC 1068 have detected a source in the 2-10 keV range with a flux density at 2 keV of 0.6 microJy. It has a flat (α_E_ = 0.62 +/- 0.25) power-law spectrum similar to type 1 Seyferts; Combined with Low Energy EXOSAT filter data and Einstein IPC observations, these data show that spectral curvature is necessary, flattening the X-ray spectrum to high energies; The spectrum can be decomposed into two components: a steep low-energy part (α_E_ ~ 3.5, kT~0.2 keV) and a flat high-energy part (α_E_~-0.3 to 1.0). Any intrinsic absorption is small (<3 x 10^20^ atoms cm^-2^). There is no evidence for variability within or between any of the observations, which sample time scales from 30 minutes to 4 yr. These data support the "obscuration" model of type 2 Seyfert galaxies in which the nucleus is seen only in flux scattered from above a "wall" of material that completely blocks the direct view. The lack of absorption implies that electron scattering, rather than dust scattering is involved. Since the absorption is also less than is seen toward the narrow emission lines a nonspherical dust geometry is strongly suggested. The reddening to the broad emission lines should then be the same small value as to the X-ray continuum.