NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T14:33:17 PDT
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For refcode 2014MNRAS.439.3931E:
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Copyright by Royal Astronomical Society. 2014MNRAS.439.3931E General relativistic modelling of the negative reverberation X-ray time delays in AGN Emmanoulopoulos, D.; Papadakis, I. E.; Dovciak, M.; McHardy, I. M. Abstract. We present the first systematic physical modelling of the time-lag spectra between the soft (0.3-1 keV) and the hard (1.5-4 keV) X-ray energy bands, as a function of Fourier frequency, in a sample of 12 active galactic nuclei which have been observed by XMM-Newton. We concentrate particularly on the negative X-ray time-lags (typically seen above 10^-4^ Hz), i.e. soft-band variations lag the hard-band variations, and we assume that they are produced by reprocessing and reflection by the accretion disc within a lamp-post X-ray source geometry. We also assume that the response of the accretion disc, in the soft X-ray bands, is adequately described by the response in the neutral Fe Kalpha line at 6.4 keV for which we use fully general relativistic ray-tracing simulations to determine its time evolution. These response functions, and thus the corresponding time-lag spectra, yield much more realistic results than the commonly used, but erroneous, top-hat models. Additionally, we parametrize the positive part of the time-lag spectra (typically seen below 10^-4^ Hz) by a power law. We find that the best-fitting black hole (BH) masses, M, agree quite well with those derived by other methods, thus providing us with a new tool for BH mass determination. We find no evidence for any correlation between M and the BH spin parameter, {alpha}, the viewing angle, theta, or the height of the X-ray source above the disc, h. Also on average, the X-ray source lies only around 3.7 gravitational radii above the accretion disc and theta is distributed uniformly between 20^degree^ and 60^degree^. Finally, there is a tentative indication that the distribution of {alpha} may be bimodal above and below 0.62. Key words: accretion, accretion discs, black hole physics, relativistic processes, galaxies: active, galaxies: nuclei, X-rays: galaxies
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