Variable emission lines as evidence of spiral shocks in accretion disks around active galactic nuclei

We show that the observed variability of the double-peaked broad emission lines seen in some active galactic nuclei can be due to the existence of two-armed spiral shocks in accretion disks around central black holes. We successfully fit the observations of Arp 102B and 3C 390.3 made at different times with self-similar spiral shock models which incorporate relativistic corrections. Our model allows predictions of how the double-peaked lines are likely to vary, so that it may be tested against future observations.