Iron K-alpha Fluorescent Line Profiles from Spiral Accretion Flows in AGNs

Abstract

We present 6.4 keV iron K-alpha fluorescent line profiles predicted for a relativistic black hole accretion disk in the presence of a spiral motion in Kerr geometry, the work extended from an earlier literature motivated by recent magnetohydrodynamic (MHD) simulations. The velocity field of the spiral motion, superposed on the background Keplerian flow, results in a complicated redshift distribution in the accretion disk. An X-ray source attributed to a localized flaring region on the black hole symmetry axis illuminates the iron in the disk. The emissivity form becomes very steep because of the light bending effect from the primary X-ray source to the disk. The predicted line profile is calculated for various spiral waves, and we found, regardless of the source height, that: (i) a multiple-peak along with a classical double-peak structure generally appears, (ii) such a multiple-peak can be categorized into two types, sharp sub-peaks and periodic spiky peaks, (iii) a tightly-packed spiral wave tends to produce more spiky multiple peaks, whereas (iv) a spiral wave with a larger amplitude seems to generate more sharp sub-peaks, (v) the effect seems to be less significant when the spiral wave is centrally concentrated, (vi) the line shape may show a drastic change (forming a double-peak, triple-peak or multiple-peak feature) as the spiral wave rotates with the disk. Our results emphasize that around a rapidly-rotating black hole an extremely redshifted iron line profile with a noticeable spike-like feature can be realized in the presence of the spiral wave. Future X-ray observations, from {\it Astro-E2} for example, will have sufficient spectral resolution for testing our spiral wave model which exhibits unique spike-like features.

30 pages, 10 figures, submitted to ApJ, will be presented at 204th Meeting of AAS in Denver

References in corpus (4)

• Fluorescent iron lines as a probe of astrophysical black hole systems
• A long hard look at MCG-6-30-15 with XMM-Newton
• Global Three-Dimensional Simulations of Black Hole Accretion Disks: X-ray Flares in the Plunging Region
• The variability of accretion onto Schwarzschild black holes from turbulent magnetized discs

Cited by in corpus (15)

• Gravitational Lensing by Black Holes
• Accretion Disk Illumination in Schwarzschild and Kerr Geometries: Fitting Formulae
• Iron line profiles and self-shadowing from relativistic thick accretion discs
• The structure and X-ray radiation spectra of illuminated accretion disks in AGN. III. Modeling fractional variability
• An outburst scenario for the X-ray spectral variability in 3C 111
• X-ray spectroscopy in the microcalorimeter era III: line formation under Case A, Case B, Case C, and Case D in H- and He-like iron for a photoionized cloud
• On the Prospect of Constraining Black-Hole Spin Through X-ray Spectroscopy of Hotspots
• Theoretical aspects of relativistic spectral features
• Modulated X-ray Emissivity near the Stress Edge in Sgr A*
• Radiation from an emitter revolving around a magnetized non-rotating black hole
• An XMM-Newton view of the X-ray flat radio-quiet quasar PG 1416-129
• Generally Applicable Formalism for Modeling the Observable Signatures of Inflows, Outflows, and Moving Coronal Plasma Close to Kerr Black Holes
• Reflection Spectra of Accretion Disks Illuminated by an Off-Axis Corona
• The Profiles of Fe Kα Line From the Inhomogeneous Accretion Flow
• Flares from spiral waves by lensing and time-delay amplification?