X-ray and soft -ray spectra of broad-line radio galaxies
| Autor: | David Smith, Greg Madejski, W. Neil Johnson, Andrzej A. Zdziarski, Przemyslaw Wozniak |
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| Rok vydání: | 1998 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences Radio galaxy Astrophysics (astro-ph) Spectral properties X-ray Solid angle FOS: Physical sciences Astronomy and Astrophysics Gamma ray spectra Astrophysics 01 natural sciences Energy index Spectral line Space and Planetary Science 0103 physical sciences 010303 astronomy & astrophysics Equivalent width 0105 earth and related environmental sciences |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 299:449-466 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1046/j.1365-8711.1998.01831.x |
| Popis: | We study X-ray and soft gamma-ray spectral properties of BLRGs using data from Ginga, ASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic power-law continuum with an energy index of alpha ~ 0.7, moderately absorbed by a cold medium. In addition, the Ginga spectra show Fe K-alpha lines with an average equivalent width of ~ 100 eV, and, in some cases, Compton reflection humps. However, the latter components are significantly weaker than both those seen in radio-quiet Seyferts and those expected if the Fe K-alpha lines were due to reflection. Some ASCA and EXOSAT spectra show soft X-ray excesses below ~ 3 keV. When that component is taken into account, the Fe K-alpha lines in the ASCA data become unresolved with equivalent widths < 200 eV. Multiple observations of 3C 390.3 and 3C 382 show the Fe K-alpha line approximately constant in flux but accompanied by strong continuum variations. This indicates the bulk of the line is formed by matter at a distance much larger than an accretion-disk scale, consistent with the ASCA line width measurements. The column density of the matter required to account for the observed line fluxes is N_H > 10^23 cm^-2. Such a medium is in the line-of-sight in 3C 445 but it has to be out of it in other objects, in which the observed N_H are substantially lower. Thus, a cold medium with that N_H and covering a large solid angle is out of the line-of-sight in most objects. The spectra of BLRGs break and become softer above ~ 100 keV, as shown by a simultaneous ASCA/OSSE observation of 3C 120 and by the OSSE spectra being on average much softer than the X-ray spectra. Finally, we find the X-ray and gamma-ray spectral properties of Cen A intrinsically very similar to BLRGs studied here. 20 pages, 13 figures, to appear in MNRAS |
| Databáze: | OpenAIRE |
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