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Frequency-dependent time lags in the X-ray emission of the Seyfert galaxy NGC 7469

I. E. Papadakis·K. Nandra·D. Kazanas
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Abstract

We report the discovery of time lags in the cross-spectra of the X-ray light curves of the Seyfert galaxy NGC 7469. This behavior is common in Galactic black hole and neutron star binaries, and is in the sense that harder X-rays are delayed with respect to the soft with a time lag approximately proportional to the Fourier period. At the longest period probed by our observation we find a time lag of approximately 3.5 hours between the 2-4 and 4-10 keV X-rays. A similar lag and period dependence is found comparing the 2-4 and 10-15 keV light curves, albeit with less significance. We find the coherence function of the light curves to be close to 1. The implications of these results for the X-ray production mechanism in active galactic nuclei (AGN) is discussed.

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I. E. Papadakis, K. Nandra, D. Kazanas. 2001-06-10. Frequency-dependent time lags in the X-ray emission of the Seyfert galaxy NGC 7469. https://doi.org/10.1086/321722

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