The X/gamma-ray spectral properties of NGC 7172

We present a combined, non-simultaneous, ASCA GIS and CGRO OSSE spectrum of the Seyfert 2 galaxy, NGC 7172, and make broad band spectral fits. The only Seyfert 2 galaxy previously studied over such a broad band is NGC 4945. We find that the most probable model for the data is a power law with an exponential cut-off being affected by a neutral absorber. The best fit parameters are found to be $\mathrm{\Gamma }=1.47\pm 0.15$ and $\text{NH}=(7.8\pm 0.6){10}^{22}$ cm${}^{-2}$. The spectral index of the underlying power law of NGC 7172 has therefore varied from 1.8 to 1.5 since the Ginga observations in 1989. For this simple model the e-folding energy at $88_{-28}^{+65}$ keV is relatively well constrained. The observed flux in the 2-10 keV range is $F_{2-10}={4.710}^{-11}$ erg cm${}^{-2}$ s${}^{-1}$, which corresponds to a small increase since the Ginga measurement in October 1989.