Can the relativistic light bending model explain X-ray spectral variations of Seyfert galaxies?

Abstract

Many Seyfert galaxies are known to exhibit Fe-K broad emission line features in their X-ray energy spectra. The observed lines have three distinct features; (1) the line profiles are skewed and show significant low-energy tails, (2) the Fe-K band have low variability, which produces a broad and deep dip in the root-mean-square (rms) spectra, and (3) photons in this band have time lags behind those in the adjacent energy bands with amplitudes of several $R_g/c$, where $R_g$ is the gravitational radius. The "relativistic light bending model" is proposed to explain these observed features, where a compact X-ray source (lamp post) above an extreme Kerr black hole illuminates the innermost area of the accretion disc. In this paper, we critically examine the relativistic light bending model by computing the rms spectra and the lag features using a ray-tracing technique, when a lamp post moves vertically on the black hole spin axis. As a result, we found that the observed deep rms dip requires that the iron is extremely overabundant ($\gtrsim 10$ solar), whereas the observed lag amplitude is consistent with the normal iron abundance. Furthermore, disappearance of the lag in the high-flux state requires a source height as high as $\sim 40R_g$, which contradicts the relativistically broad emission line feature. Our simulations agree with the data that the reverberation feature moves to lower frequencies with larger source height, however, if this scenario is correct, the simulations predict detection of a clear Fe-K lag at low frequencies, which is not constrained in the data. Therefore, we conclude that the relativistic light bending model may not explain the characteristic Fe-K spectral variations in Seyfert galaxies.

arXiv comment17 pages, 15 figures, accepted by PASJ

References in corpus (36)

• Evidence for ultra-fast outflows in radio-quiet AGNs: I - detection and statistical incidence of Fe K-shell absorption lines
• A light bending model for the X-ray temporal and spectral properties of accreting black holes
• RXTE Observation of Cygnus X-1: II. Timing Analysis
• X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180
• X-Ray Variability Coherence: How to Compute it, What it Means, and How it Constrains Models of Cyg X-1 and GX 339-4
• A global look at X-ray time lags in Seyfert Galaxies
• X-ray variability of 104 active galactic nuclei. XMM-Newton power-spectrum density profiles
• The lack of variability of the iron line in MCG-6-30-15: general relativistic effects
• X-ray iron line reverberation from black hole accretion disks
• The iron line in MCG-6-30-15 from XMM-Newton: evidence for gravitational light-bending?
• Relativistic iron K X-ray Reverberation in NGC 4151
• How the X-ray spectrum of a Narrow-Line Seyfert 1 galaxy may be reflection dominated
• ROSAT monitoring of persistent giant and rapid variability in the narrow-line Seyfert 1 galaxy IRAS 13224-3809
• The response of relativistic outflowing gas to the inner accretion disk of a black hole
• Modelling the broad Fe Kα reverberation in the AGN NGC 4151
• General relativistic modelling of the negative reverberation X-ray time delays in AGN
• Long XMM observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809: rapid variability, high spin and a soft lag
• The origin of the lag spectra observed in AGN: Reverberation and the propagation of X-ray source fluctuations
• The Closest Look at 1H0707-495: X-ray Reverberation Lags with 1.3 Ms of Data
• Revealing the X-ray source in IRAS 13224-3809 through flux-dependent reverberation lags
• Partial Covering Interpretation of the X-Ray Spectrum of the NLS1 1H 0707-495
• The origin of ultra-fast outflows in AGN: Monte-Carlo simulations of the wind in PDS 456
• A disk wind interpretation of the strong Fe Kα features in 1H 0707-495
• XMM-Newton spectral properties of the Narrow-Line Seyfert 1 galaxy IRAS 13224--3809
• Modelling the Extreme X-ray Spectrum of IRAS 13224-3809
• X-Ray Spectral Variability of the Seyfert Galaxy NGC 4051 Observed with Suzaku
• A 10-day ASCA Observation of the Narrow-line Seyfert~1 galaxy IRAS 13224-3809
• A Variable Partial Covering Model for the Seyfert 1 Galaxy MCG-6-30-15
• How well can we measure supermassive black hole spin?
• Interpretation of the X-ray Spectral Variation of 1H0707-495 with a Variable Double Partial Covering Model
• Suzaku Discovery of a Hard Component Varying Independently of the Power-Law Emission in MCG-6-30-15
• GR models of the X-ray spectral variability of MCG--6-30-15
• Origin of the Broad Iron Line Feature and the Soft X-ray Variation in Seyfert Galaxies
• New method for black-hole spin measurement based on flux variation from an infalling gas ring
• Origin of the Characteristic X-ray Spectral Variations of IRAS 13224$-$3809
• On the light-bending model of X-ray variability of MCG-6-30-15

Cited by in corpus (2)

• A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
• X-ray reverberation lags of the Fe-K line due to AGN disc winds