The origin of the correlation between the UV and X - rays in NGC 4151
نویسنده
چکیده
We propose that the UV/X-ray correlation observed in NGC 4151 by EXOSAT and IUE is due to reemission of the X-ray flux absorbed by cold clouds in the line of sight. This transmission model satisfies the energy balance, provides a good fit to the X-ray and UV data, and predicts no Compton reflection of X-rays (as observed). The correlation can alternatively be explained by reprocessing of X-rays and γ-rays by a cold accretion disk. A specific model in which X-rays and γ-rays are emitted by a dissipative patchy corona and have the spectrum cut off at ∼ 100 keV (as seen by OSSE) is shown to be energetically possible even if it does not give as satisfactory a fit as the transmission model. However, the model predicts a Compton-reflection spectral component, whose presence remains to be tested by future detectors sensitive above 10 keV.
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