The flux-dependent X-ray time lags in NGC 4051

  title={The flux-dependent X-ray time lags in NGC 4051},
  author={William N. Alston and Simon Vaughan and Phil Uttley},
  journal={Monthly Notices of the Royal Astronomical Society},
We present an analysis of the X-ray time lags for the highly variable Seyfert 1 galaxy NGC 4051, based on a series of XMM-Newton observations taken in 2009. We investigate the Fourier frequency dependent time lags in the light curves between the 0.3-1.0 keV and 2.0-5.0 keV energy bands as a function of source flux, including simultaneous modelling of the resulting lag-frequency spectra. We find the shape of the lag-frequency spectra to vary significantly and systematically with source flux. We… 

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