Narrow moving FeKα lines from magnetic flares in active galactic nuclei

We show that luminous magnetic flares, thought to occur in standard accretion disks in active galactic nuclei, cannot be located much higher than a few pressure scale heights above the disk. Using this fact, we estimate the fraction of the disk surface illuminated by a typical flare to be very small for geometrically thin disks, which implies that the instantaneous Fe K alpha emission line from a specific magnetic flare is narrow. The line is red- or blueshifted depending on the position of the observer relative to the flare and sweeps across the line band with time. We present several examples of theoretical time-resolved line profiles from such flares for Schwarzschild geometry. Search for such moving features with future X-ray telescopes will present a powerful test of the accretion disk geometry; if observed, these features may let us test general relativity in the strong field limit.