The effects of relativistic bulk motion of X-ray flares in the corona on the iron Kalpha line in Seyfert 1 galaxies

Abstract

We study the effects of the bulk motion of X-ray flares on the shape and equivalent width of the iron Kalpha line from an untruncated cold disk around a Kerr black hole using fully relativistic calculations. The flares are located above a cold accretion disk -- either on or off the rotation axis. For on- or off-axis flares, the upward/outward bulk motion causes a reduction of the iron Kalpha line width. To a distant observer with a low inclination angle (θ_o \simlt 30deg.), larger upward/outward bulk velocities decrease the extension of the red wing, with little change in the location of the blue `edge'. In contrast, an observer at a large inclination angle (e.g. θ_o=60deg.) sees both the red wing and the blue `edge' change with the bulk velocity. The equivalent width of the iron Kalpha line decreases rapidly with increasing bulk velocity of flares. However, the `narrower' line profiles observed in some objects (e.g. IC4329A and NGC4593) are difficult to produce using the out-flowing magnetic flare model with an appropriate equivalent width unless the X-ray emission is concentrated in an outer region with a radius of several tens of r_g=GM/c^2 or more. An important result is that the iron Kalpha line intensity is found to be constant even though the continuum flux varies significantly, which is true for out-flowing magnetic flares with different bulk velocities but similar intrinsic luminosities when located close to the central black hole. We find that fluctuations in the bulk velocities of out-flowing low-height flares located at the inner region (r\simlt 15r_g) can account for a constant iron Kalpha line and significant continuum variation as observered in MCG-6-30-15 and NGC5548. (Abridged)

arXiv comment30 pages (including 8 figures); minor changes, to appear in ApJ, Nov. 10, 2001

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• Accretion disks and coronae in the X-ray flashlight
• X-Ray Properties of Narrow-Line Seyfert 1 Galaxies with Very Small Broad-Line Widths
• On Testing the Kerr Metric of the Massive Black Hole in the Galactic Center via Stellar Orbital Motion: Full General Relativistic Treatment
• On variability and spectral distortion of the fluorescent iron lines from black-hole accretion discs
• Prospects for constraining the spin of the massive black hole at the Galactic center via the relativistic motion of a surrounding star
• The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object
• The scaling of X-ray variability with luminosity in Ultra-luminous X-ray sources
• Iron line profiles and self-shadowing from relativistic thick accretion discs
• NGC 2992 in an X-ray high state observed by XMM: Response of the Relativistic Fe K$\alpha$ Line to the Continuum
• An intense and broad FeKalpha line observed in the X-ray luminous quasar Q0056-363 with XMM-Newton
• Broad reprocessed Balmer emission from warped accretion discs
• Iron K-alpha Fluorescent Line Profiles from Spiral Accretion Flows in AGNs
• Testing the binary black hole paradigm through the Fe Kalpha line profile: application to 3C 273
• Flare-induced fountains and buried flares in AGN
• Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona
• Probing the precession of the inner accretion disk in Cygnus X-1
• X-ray Eclipses of Active Galactic Nuclei
• Inferring the coronal flaring patterns in AGN from reverberation maps