THE CANONICAL X-RAY GAMMA-RAY SPECTRUM OF SEYFERT 1S AND LOW-STATE GALACTIC BLACK-HOLE CANDIDATES/

We review broad-band X-ray/gamma-ray spectra of radio-quiet Seyfert 1s as well as of Galactic black hole candidates in the low state. The sp ectra share their basic components: an underlying power law, a Compton -reflection component with an Fe K alpha line, low-energy absorption b y cold matter, and a high-energy cutoff above similar to 200 keV. The X-ray energy spectral index, ct, is in the range similar to 0.8-1 in t he average Seyfert-1 spectra from Ginga, EXOSAT and OSSE and in the av ailable X-ray/gamma-ray spectra of bright Seyfert 1s. The low-state sp ectra of Cyg X-1 and GX 339-4 from simultaneous Ginga/OSSE observation s have alpha similar or equal to 0.6-0.8. The Compton-reflection compo nent corresponds to cold matter (e.g., inner or outer parts of an accr etion disk) covering a solid angle of similar to (0.4-0.8) X 2 pi as s een from the X-ray source. Cutoffs in soft gamma-rays correspond to th e plasma temperature of order of 100 keV. The intrinsic spectra are we ll explained by thermal Comptonization in plasmas with the Thomson opt ical depth of tau similar to 1.