摘要：Aims. We provide an alternative to existing theories for the origin of linear rms–mean flux relations observed in a variety of accreting systems, from AGN to white dwarfs.
Methods. Standard statistical theory and simulations are used to explore the possibility that the relations are due to simple scaling effects.
Results. The proposed theory can reproduce the unit slope of the rms–mean flux relation observed in the most extensive study published to date. The close similarity of the fractional variability in different objects deserves further study.
