On the Evidence for Extreme Gravity Effects in MCG-6-30-15

Abstract

We examine the unusual Fe-Kalpha line profile in MCG-6-30-15 observed by ASCA during a deep minimum in the source intensity. The intense red wing and depressed blue wing of the line have been interpreted as evidence for extreme gravitational redshifts in terms of emission from within six gravitational radii of a black hole. We find that the data do not uniquely support this interpretation and can be equally well explained by occultation of the continuum source and the putative line-emitting accretion disk, which we offer as an alternative hypothesis. Two problems with previous modeling were that the equivalent width of the line during the deep minimum was required to be unusually large (> 1 keV) and the line intensity was thought to increase as the source became dim. The occultation model does not suffer from these problems. Our results serve to highlight the hazards of over-interpreting observational results which have low statistical significance, to the extent that theoretical implications can become generally accepted when the data do not provide a strong case for them.

Accepted for publication in The Astrophysical Journal Letters. Latex and 5 postscript figures; 13 pages including figures

References in corpus (5)

• Iron fluorescence from within the innermost stable orbit of black hole accretion disks
• The profile and equivalent width of the X-ray iron emission-line from a disk around a Kerr black hole
• Occultation Mapping of the Central Engine in the Active Galaxy MCG -6-30-15
• On the Origin of Broad Fe K alpha and Hi H alpha Lines in AGN
• A Simple New Method For Analysing Gapped Time-Series: Search For a High Frequency Cut-off In The X-ray Power Spectrum of MCG -6-30-15

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• Variable Iron K-alpha Lines in Seyfert 1 Galaxies
• Ripple effects & oscillations in the broad FeKa line as a probe of massive black hole mergers
• Reprocessed emission from warped accretion discs with application to X-ray iron line profiles
• Variable line profiles due to non-axisymmetric patterns in an accretion disc around a rotating black hole
• Iron line profiles from black hole accretion discs with spiral velocity structure
• Comparisons of various model fits to the Iron line profile in MCG-6-30-15
• Estimation of relativistic accretion disk parameters from iron line emission
• Eclipsing light curves for accretion flows around a rotating black hole and atmospheric effects of the companion star
• A two zone model for the broad Iron line emission in MCG-6-30-15