Modelling the extreme X-ray spectrum of IRAS 13224−3809

Chiang, Chia-Ying; Walton, D. J.; Fabian, A. C.; Wilkins, D. R.; Gallo, Luigi

doi:10.1093/mnras/stu2087

Cited by 59 publications

(93 citation statements)

References 56 publications

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“…It is hard to be sure of the exact nature of this component from variability alone. It could represent a second process contributing to the soft excess, such as Comptonization, or it could be due to a second, higher ionization, reflection component, as found by previous studies of this source (Fabian 2013;Chiang et al 2015). We will discuss this more in future work, where we will explore the nature of the soft excess with several different methods.…”

Section: Discussionmentioning

confidence: 73%

Revealing the ultrafast outflow in IRAS 13224−3809 through spectral variability

Parker

Alston

Buisson

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the long-term X-ray variability of the extreme narrow-line Seyfert 1 (NLS1) galaxy IRAS 13224-3809 using principal component analysis (PCA) and fractional excess variability (F var ) spectra to identify model-independent spectral components. We identify a series of variability peaks in both the first PCA component and F var spectrum which correspond to the strongest predicted absorption lines from the ultra-fast outflow (UFO) discovered by Parker et al. (2017). We also find higher order PCA components, which correspond to variability of the soft excess and reflection features. The subtle differences between RMS and PCA results argue that the observed flux-dependence of the absorption is due to increased ionization of the gas, rather than changes in column density or covering fraction. This result demonstrates that we can detect outflows from variability alone, and that variability studies of UFOs are an extremely promising avenue for future research.

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Section: Discussionmentioning

confidence: 73%

Revealing the ultrafast outflow in IRAS 13224−3809 through spectral variability

Parker

Alston

Buisson

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…For a black hole with a mass of MBH = 10 7 M , which is a conservative value for our source and NLS1 in general (see e.g. Chiang et al 2015), the Eddington limit L Edd = 3.2 × 10 4 (MBH/M )L is reached at about 1.3 × 10 45 erg s −1 . We can estimate the bolometric luminosity through the hard X-ray (2-10 keV) to bolometric luminosity correction according to Vasudevan & Fabian (2007).…”

Section: High Eddington Accretion?mentioning

confidence: 99%

Ultrafast outflows disappear in high-radiation fields

Pinto

Alston

Parker

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Ultrafast outflows (UFOs) are the most extreme winds launched by active galactic nuclei (AGN) due to their mildly-relativistic speeds (∼ 0.1 − 0.3c) and are thought to significantly contribute to galactic evolution via AGN feedback. Their nature and launching mechanism are however not well understood. Recently, we have discovered the presence of a variable UFO in the narrow-line Seyfert 1 IRAS 13224−3809. The UFO varies in response to the brightness of the source. In this work we perform fluxresolved X-ray spectroscopy to study the variability of the UFO and found that the ionisation parameter is correlated with the luminosity. In the brightest states the gas is almost completely ionised by the powerful radiation field and the UFO is hardly detected. This agrees with our recent results obtained with principal component analysis. We might have found the tip of the iceberg: the high ionisation of the outflowing gas may explain why it is commonly difficult to detect UFOs in AGN and possibly suggest that we may underestimate their actual feedback. We have also found a tentative correlation between the outflow velocity and the luminosity, which is expected from theoretical predictions of radiation-pressure driven winds. This trend is rather marginal due to the Fe XXV-XXVI degeneracy. Further work is needed to break such degeneracy through time-resolved spectroscopy.

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“…Fabian et al 2013;Chiang et al 2015). This is because the particular spectral shape of the VDPC model (eq.2) has strong spectral troughs at iron L-and K-edges even with the solar abundance.…”

Section: Interpretation Of the Spectral Variationsmentioning

confidence: 99%

Origin of the characteristic X-ray spectral variations of IRAS 13224−3809

Yamasaki

Mizumoto

Ebisawa

et al. 2016

Publications of the Astronomical Society of Japan

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The Narrow-line Seyfert 1 galaxy (NLS1) IRAS 13224−3809 is known to exhibit significant Xray spectral variation, a sharp spectral drop at ∼ 7 keV, strong soft excess emission, and a hint of iron L-edge feature, which is very similar to the NLS1 1H 0707−495. We have proposed the "Variable Double Partial Covering (VDPC) model" to explain the energy spectra and spectral variability of 1H 0707−495 (Mizumoto, Ebisawa and Sameshima 2014, PASJ, 66, 122). In this model, the observed flux/spectral variations below 10 keV within a ∼day are primarily caused by change of the partial covering fraction of patchy clouds composed by double absorption layers in the line of sight. In this paper, we apply the VDPC model to IRAS 13224−3809. Consequently, we have found that the VDPC model can explain the observed spectral variations of IRAS 13224-3809 in the 0.5-10 keV band. In particular, we can explain the observed Root Mean Square (RMS) spectra (energy dependence of the fractional flux variation) in the entire 0.5 -10 keV band. In addition to the well-known significant drop in the iron K-band, we have found intriguing iron L-peaks in the RMS spectra when the iron L-edge is particularly deep. This feature, which is also found in 1H 0707-495, is naturally explained with the VDPC model, such that the RMS variations increase at the energies where optical depths of the partial absorbers are large. The absorbers have a larger optical depth at the iron L-edge than in the adjacent energy bands, thus a characteristic iron L-peak appears. On the other hand, just below the iron K-edge, the optical depth is the lowest and the RMS spectrum has a broad dip.

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Modelling the extreme X-ray spectrum of IRAS 13224−3809

Cited by 59 publications

References 56 publications

Revealing the ultrafast outflow in IRAS 13224−3809 through spectral variability

Revealing the ultrafast outflow in IRAS 13224−3809 through spectral variability

Ultrafast outflows disappear in high-radiation fields

Origin of the characteristic X-ray spectral variations of IRAS 13224−3809

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