Illuminating black holes with tidal disruption events

Andrew Mummery (Oxford)

When an unfortunate star is perturbed onto a near-radial orbit about the supermassive black hole in its galactic centre, it can be destroyed, in its entirety, by the extreme tidal forces of the black holes spacetime.

The subsequent accretion of these stellar debris powers luminous flares observed across the electromagnetic spectrum and out to cosmological distances. These so-called tidal disruption events (TDEs) have the potential to answer a number of questions of contemporary astrophysical interest. They naturally probe the mass and spin distributions of supermassive black holes, the mass distribution of the stars in galactic centres, and will even offer insight into questions of fundamental physics. 

Forthcoming optical surveys (such as Ruben/LSST) will transform TDE science as we transition from finding one TDE roughly every month, to one TDE roughly every hour. 

I will discuss my recent work in the analysis of late time optical/UV data from TDEs, utilising new developments in the theory of time dependent and relativistic accretion flows. A single observation of the late time optical/UV emission from a TDE can now be used to measure the central black holes mass with only 0.5 dex of scatter.

I will argue that this breakthrough will allow the properties of the supermassive black hole mass and spin distributions to be measured, which will offer key insights into questions regarding their formation and evolution. I will finish by discussing how the insights gained from studying the late time emission of TDEs can be used to understand the growing populations of novel transients discovered by optical surveys, such as the now-famous luminous FBOT AT2018cow.