Spectral variability analysis of an XMM-Newton observation of Ark 564

Abstract

We present a spectral variability analysis of the X-ray emission of the Narrow Line Seyfert 1 galaxy Ark 564 using the data from a ~100 ks XMM-Newton observation. Taking advantage of the high sensitivity of this long observation and the simple spectral shape of Ark 564, we determine accurately the spectral variability patterns in the source. We use standard cross-correlation methods to investigate the correlations between the soft and hard energy band light curves. We also generated 200 energy spectra from data stretches of 500 s duration each and fitted each one of them with a power law plus a bremsstrahlung component (for the soft excess) and we investigated the correlations between the various best fit model parameter values. The ``power law plus bremsstrahlung'' model describes the spectrum well at all times. The iron line and the absorption features, which are found in the time-averaged spectrum of the source are too weak to effect the results of the time resolved spectral fits. We find that the power law and the soft excess flux are variable, on all measured time scales. The power law slope is also variable, and leads the flux variations of both the power law and the bremsstrahlung components. Our results can be explained in the framework of time-dependent Comptonization models. They are consistent with a picture where instabilities propagate through an extended X-ray source, affecting first the soft and then the hard photons producing regions. The soft excess could correspond to ionized disc reflection emission, in which case it responds fast to the primary continuum variations. The time scales are such that light travel times might additionally influence the observed variability structure.

arXiv comment11 pages, 11 figures. accepted for publication by A&A

References in corpus (24)

• On characterising the variability properties of X-ray light curves from active galaxies
• An Explanation for the soft X-ray excess in AGN
• Is the soft excess in AGN real?
• Investigating a Fluctuating-accretion Model for the Spectral-timing Properties of Accreting Black Hole Systems
• X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180
• A Model for the X-Ray and UV Emission from Seyfert Galaxies and Galactic Black Holes
• A Comprehensive Spectral and Variability Study of Narrow-Line Seyfert 1 Galaxies Observed by ASCA: I. Observations and Time Series Analysis
• XMM-Newton study of the complex and variable spectrum of NGC 4051
• Accretion disc coronae as magnetic reservoirs
• Universal spectral shape of high accretion rate AGN
• X-ray variability and correlations in the two phase disk-corona model for Seyfert galaxies
• Exploring NLS1 through the physical properties of their hosts
• Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. I. ASCA Observations and the Variability of the X-ray Spectral Components
• Spectral-timing evidence for a Very High State in the Narrow Line Seyfert 1 Ark 564
• Detection of a high frequency break in the X-ray power spectrum of Ark 564
• XMM-Newton timing mode observations of Mrk 421
• X-ray Power Density Spectrum of the Narrow Line Seyfert 1 Galaxy Akn 564
• The Spectral Energy Distribution and Emission-Line properties of the NLS1 Galaxy Arakelian 564
• XMM-Newton observation of the NLS1 Galaxy Ark 564: I. Spectral analysis of the time-average spectrum
• BeppoSAX observations of Narrow-Line Seyfert 1 galaxies: II. Ionized iron features in Arakelian 564
• Akn 564: an unusual component in the X-ray spectra of NLSy1 galaxies
• Arakelian 564: An XMM-Newton view
• On the Nature of X-ray Variability in Ark 564
• X-ray variability of the Narrow Line Seyfert 1 Galaxy PKS 0558-504

Cited by in corpus (6)

• Discovery of multiple Lorentzian components in the X-ray timing properties of the Narrow Line Seyfert 1 Ark 564
• An investigation of the origin of soft X-ray excess emission from Narrow-line Seyfert 1 galaxies Akn564 and Mrk1044
• An XMM-Newton view of the `bare' nucleus of Fairall 9
• A Two-Phase Low-velocity Outflow in the Seyfert 1 Galaxy Ark~564
• UV and X-Ray Variability of the Narrow-Line Seyfert 1 Galaxy Ark 564
• X-ray warm absorber variability of the Seyfert Galaxy Arakelian 564