088213

Iron lines are observed ubiquitously in AGN comma offering a powerful probe of the black hole surroundings. Mrk 841 provides a puzzling case in which the narrow iron line comma usually associated with the torus or the broad line region comma varies on hours time scales. This can be due either an unusually small emission region for the narrow line comma or due to hot spots orbiting very close to the black hole whose emission is occasionally Doppler-boosted. With the source visibility now allowing for long exposures comma we propose to observe it for two orbits comma simultaneously with NuSTAR comma to solve the puzzle. Confirming any of the proposed mechanisms offer an exciting opportunity to unravel unprecedented details about the line emission region.