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

We examine the unusual Fe-Kalpha line profile in MCG-6-30-15 observed by ASCAduring a deep minimum in the source intensity. The intense red wing anddepressed blue wing of the line have been interpreted as evidence for extremegravitational redshifts in terms of emission from within six gravitationalradii of a black hole. We find that the data do not uniquely support thisinterpretation and can be equally well explained by occultation of thecontinuum source and the putative line-emitting accretion disk, which we offeras an alternative hypothesis. Two problems with previous modeling were that theequivalent width of the line during the deep minimum was required to beunusually large (> 1 keV) and the line intensity was thought to increase as thesource became dim. The occultation model does not suffer from these problems.Our results serve to highlight the hazards of over-interpreting observationalresults which have low statistical significance, to the extent that theoreticalimplications can become generally accepted when the data do not provide astrong case for them.Comment: Accepted for publication in The Astrophysical Journal Letters. Latex and 5 postscript figures; 13 pages including figure