High-energy X-ray observations of NGC 4151 with a balloon-borne telescope

3U 1207 + 39, the X-ray source identified with the Seyfert galaxy NGC 4151, was observed on 1975 June 24 with a balloon-borne telescope. The photon number spectrum was relatively flat (power-law slope $$\alpha=-1.6\pm0.9$$) and consistent with previous observations. Thermal brems-strahlung models provide poorer fits to the data.