Revealing structure and evolution within the corona of the Seyfert galaxy IZw1

D. R. Wilkins, L. C. Gallo, C. V. Silva, E. Costantini, W. N. Brandt, G. A. Kriss

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26 Scopus citations


X-ray spectral timing analysis is presented of XMM-Newton observations of the narrow-line Seyfert 1 galaxy I Zwicky 1 taken in 2015 January. After exploring the effect of background flaring on timing analyses, X-ray time lags between the reflection-dominated 0.3-1.0 keV energy and continuum-dominated 1.0-4.0 keV band are measured, indicative of reverberation offthe inner accretion disc. The reverberation lag time is seen to vary as a step function in frequency; across lower frequency components of the variability, 3 × 10-4-1.2 × 10-3 Hz a lag of 160 s is measured, but the lag shortens to (59±4) s above 1.2×10-3 Hz. The lag-energy spectrum reveals differing profiles between these ranges with a change in the dip showing the earliest arriving photons. The low-frequency signal indicates reverberation of X-rays emitted from a corona extended at low height over the disc, while at high frequencies, variability is generated in a collimated core of the corona through which luminosity fluctuations propagate upwards. Principal component analysis of the variability supports this interpretation, showing uncorrelated variation in the spectral slope of two power-law continuum components. The distinct evolution of the two components of the corona is seen as a flare passes inwards from the extended to the collimated portion. An increase in variability in the extended corona was found preceding the initial increase in X-ray flux. Variability from the extended corona was seen to die away as the flare passed into the collimated core leading to a second sharper increase in the X-ray count rate.

Original languageEnglish (US)
Pages (from-to)4436-4451
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Nov 11 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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