INTEGRAL and the Unified Model of AGN
  According to the unified model, the differences observed in different classes
of AGN are due to anisotropic obscuration. This implies that in the hard
X-rays, at energies where the radiation can pierce the obscuring material, the
average spectral characteristics of different classes of AGN should be the
same. Here we present a study of the 17-250 keV INTEGRAL IBIS/ISGRI average
spectra of Seyfert galaxies, aimed to constrain similarities and possible
differences between different classes of AGN. The sample we consists of all the
172 Seyfert galaxies detected by INTEGRAL IBIS/ISGRI at z<0.2 during its first
7 years of observations. Of these, 45 are Seyfert 1s, 31 Seyfert 1.5s, 67
Compton-thin Seyfert 2s, 11 Narrow Line Seyfert 1s, 11 Compton-thick Seyfert
2s, and 9 LINERs. Comparing the average hard X-ray spectra of the different
classes we found that, while the spectra of Seyfert 1s, Seyfert 1.5 and NLS1s
are consistent, Compton-thin Seyfert 2 show a clear excess in the 20-60 keV
band over the spectrum of Seyfert 1s and Seyfert 1.5s. This excess might be due
to an intrinsically stronger reflection component or to a clumpy structure of
the absorber in Compton-thin Seyfert 2s.
