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تسجيل مستخدم جديدNo Signatures of Black-Hole Spin in the X-ray Spectrum of the Seyfert 1 Galaxy Fairall 9
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Fairall 9 is one of several type 1 active galactic nuclei for which it has been claimed that the angular momentum (or spin) of the supermassive black hole can be robustly measured, using the Fe K$alpha$ emission line and Compton-reflection continuum in the X-ray spectrum. The method rests upon the interpretation of the Fe K$alpha$ line profile and associated Compton-reflection continuum in terms of relativistic broadening in the strong gravity regime in the innermost regions of an accretion disc, within a few gravitational radii of the black hole. Here, we re-examine a Suzaku X-ray spectrum of Fairall 9 and show that a face-on toroidal X-ray reprocessor model involving only nonrelativistic and mundane physics provides an excellent fit to the data. The Fe K$alpha$ line emission and Compton reflection continuum are calculated self-consistently, the iron abundance is solar, and an equatorial column density of $sim 10^{24} rm cm^{-2}$ is inferred. In this scenario, neither the Fe K$alpha$ line, nor the Compton-reflection continuum provide any information on the black-hole spin. Whereas previous analyses have assumed an infinite column density for the distant-matter reprocessor, the shape of the reflection spectrum from matter with a finite column density eliminates the need for a relativistically broadened Fe K$alpha$ line. We find a 90 per cent confidence range in the Fe K$alpha$ line FWHM of $1895$-$6205 rm km s^{-1}$, corresponding to a distance of $sim 3100$ to $33,380$ gravitational radii from the black hole, or $0.015$-$0.49$ pc for a black-hole mass of $sim 1-3 times 10^{8} M_{odot}$.
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