Invited talk (I0.2) Sera Markoff (University of Amsterdam)
Putting the hair back on black holes
The physicist John Wheeler once famously said “black holes have no hair”, meaning that a black hole can be characterised by a few numbers like its mass, spin and (not relevant for astrophysical black holes) charge. However black holes end up having pretty complex “hair" when they accrete, the most dramatic being the magnetic fields driving the jets, where we know that the same mass black hole with the same spin can show drastically different outflow properties compared to other similar black holes, or even itself as it experiences state changes. In my group we have been focusing on bringing together knowledge from numerical simulations and more semi-analytical approaches to describe data from a wide range of facilities, in order to better understand what determines the "hair", i.e. the thing that makes black holes look/act differently. Understanding this is a necessary step towards more reliable models for important processes like black hole feedback and high-energy particle acceleration. I will give a few examples of some recent results from our group that illustrate the connection between what we study with EHT, and Galactic XRB transients.