Figure 2.

The left panel shows the broad iron line seen in the Seyfert I galaxy MCG–6-30-15. The line would be very narrow and centered at 6.35 keV if the emitter were at rest in the galaxy but is clearly highly distorted and skewed to lower energies. The model compared with the data (solid line) assumes that the emitter is orbiting in a disk lying between 6 and 40 GM/c², inclined at 30°. Gravitational redshift due to the deep potential well accounts for part of the skewness. The right panel compares the data taken in 1994 (red dots, also shown in A) with that from 1997. The line profile is robust.