A longer XMM-Newton look at I Zwicky 1: Variability of the X-ray continuum, absorption, and iron Kalpha line

Abstract

We present the second XMM-Newton observation (85 ks) of the narrow-line Seyfert 1 galaxy (NLS1) I Zw 1 and describe its mean spectral and timing characteristics. On average, I Zw 1 is ~35 per cent dimmer in 2005 than in the shorter (20 ks) 2002 observation. Between the two epochs the intrinsic absorption column density diminished, but there were also subtle changes in the continuum shape. Considering the blurred ionised reflection model, the long-term changes can be associated with a varying contribution of the power law component relative to the total spectrum. Examination of normalised light curves indicates that the high-energy variations are quite structured and that there are delays, but only in some parts of the light curve. Interestingly, a hard X-ray lag first appears during the most-distinct structure in the mean light curve, a flux dip ~25 ks into the observation. The previously discovered broad, ionised Fe Ka line shows significant variations over the course of the 2005 observation. The amplitude of the variations is 25-45 per cent and they are unlikely due to changes in the Fe ka-producing region, but perhaps arise from orbital motion around the black hole or obscuration in the broad iron line-emitting region. The 2002 data are re-examined for variability of the Fe Ka line at that epoch. There is evidence of energy and flux variations that are associated with a hard X-ray flare that occurred during that observation.

11 pages, 13 figures. Accepted by MNRAS. Minor revisions and expanded discussion

References in corpus (3)

• Spectral-timing evidence for a Very High State in the Narrow Line Seyfert 1 Ark 564
• Statistics of relativistically broadened Fe K-alpha lines in AGN
• On the X-ray spectra of luminous, inhomogeneous accretion flows

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• A longer XMM-Newton look at I Zwicky 1: physical conditions and variability of the ionised absorbers
• Iron line profiles and self-shadowing from relativistic thick accretion discs
• A longer XMM-Newton look at I Zwicky 1: Distinct modes of X-ray spectral variability
• The multi-epoch X-ray tale of I Zwicky 1 outflows
• A systematic study of the ultra-fast outflow responses to luminosity variations in active galactic nuclei
• Strong X-ray Variability of I Zwicky 1: Obscuration from Clumpy Accretion-Disk Winds