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Eavesdropping on accretion disks: the timing properties of accreting white dwarfs as revealed by Kepler and TESS

Event details of Simone Scaringi (Durham University)
Date 12 May 2021
Time 11:00 -12:00

Accretion is the process that drives and regulates the growth of most objects in the Universe. Understanding the role of mass transfer through viscous propagation, as well as the geometrical constituents of accretion flows, has direct implications to how essentially all stellar systems and populations form and evolve. The classical equations of disk structure and more modern magnetohydrodynamics approaches suggest that the basic physics of the accretion process should work through the same processes for all types of accretion disks. Yet, although the importance and ubiquity of accretion disks have been recognised for many years and that they may be considered scale-invariant, the detailed physics and dynamics of accretion is still poorly understood.

In this talk I will discuss why accreting white dwarfs in particular are prime systems to study and unravel the physics of accretion. I will present several results from both Kepler and TESS on the timing studies of these same systems. This will include modelling the observed broad- band variability (flickering) induced by the disks, tracking the disk geometry through disk instability outbursts, and the discovery and further follow-up of systems displaying so-called magnetically gated accretion bursts. I will conclude by introducing new data from the latest TESS observing cycles, with some targets displaying some novel, yet unexplained, variability patterns which may find close analogies to accreting neutron stars.