title: Accretion-induced variability links young stellar objects, white dwarfs, and black holes.
abstract: The central engines of disc-accreting stellar-mass black holes appear to be scaled down versions of the supermassive black holes that power active galactic nuclei. However, if the physics of accretion is universal, it should also be possible to extend this scaling to other types of accreting systems, irrespective of accretor mass, size, or type. We examine new observations, obtained with Kepler/K2 and ULTRACAM, regarding accreting white dwarfs and young stellar objects. Every object in the sample displays the same linear correlation between the brightness of the source and its amplitude of variability (rms-flux relation) and obeys the same quantitative scaling relation as stellar-mass black holes and active galactic nuclei. We also show that the most important parameter in this scaling relation is the physical size of the accreting object. This establishes the universality of accretion physics from proto-stars still in the star-forming process to the supermassive black holes at the centers of galaxies.
authors.affiliation: Max-Planck-Institut für Extraterrestriche Physik, D-85748 Garching, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Scaringi
authors.affiliation: Department of Physics, Texas Tech University, Box 41051, Lubbock, TX 79409-1051, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Maccarone
authors.affiliation: Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University Nijmegen, P. O. Box 9010, 6500 GL Nijmegen, Netherlands.
authors.forename: Elmar
authors.initials: E
authors.lastname: Körding
authors.affiliation: School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: Knigge
authors.affiliation: Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Vaughan
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Marsh
authors.affiliation: Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University Nijmegen, P. O. Box 9010, 6500 GL Nijmegen, Netherlands.
authors.forename: Ester
authors.initials: E
authors.lastname: Aranzana
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK. ; Instituto de Astrofisica de Canarias, E-38205, La Laguna, Tenerife, Spain.
authors.forename: Vikram S
authors.initials: VS
authors.lastname: Dhillon
authors.affiliation: Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, Centro de Astrofísica da Universidade do Porto (CAUP), Rua das Estrelas, PT4150-762 Porto, Portugal.
authors.forename: Susana C C
authors.initials: SC
authors.lastname: Barros
keywords: accretion; black holes; timing; unification; variability; white dwarfs; young-stellar objects