Abstract
We review broad-band X-ray/γ-ray spectra of radio-quiet Seyfert Is as well as of Galactic black hole candidates in the low state. The spectra share their basic components: an underlying power law, a Compton-reflection component with an Fe Ka line, low-energy absorption by cold matter, and a high-energy cutoff above ∼ 200 keV. The X-ray energy spectral index, a, is in the range ∼ 0.8-1 in the average Seyfert-1 spectra from Ginga, EXOSAT and OSSE and in the available X-ray/7-ray spectra of bright Seyfert Is. The low-state spectra of Cyg X-l and GX 339-4 from simultaneous Ginja/OSSE observations have a c± 0.6-0.8. The Comptonreflection component corresponds to cold matter (e.g., inner or outer parts of an accretion disk) covering a solid angle of ∼ (0.4-0.8) x 2îT as seen from the X-ray source. Cutoffs in soft 7-rays correspond to the plasma temperature of order of 100 keV. The intrinsic spectra are well explained by thermal Comptonization in plasmas with the Thomson optical depth of r ∼ 1.
Original language | English |
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Pages (from-to) | 553-558 |
Number of pages | 6 |
Journal | Astronomy and Astrophysics Supplement Series |
Volume | 120 |
Issue number | 4 |
Publication status | Published - 1 Dec 1996 |
Keywords
- Galaxies: Seyfert
- Gammarays: Observations
- Radiation mechanisms: Thermal
- Stars: Individual: Cyg x-1
- X-rays: Galaxies
ASJC Scopus subject areas
- General Physics and Astronomy