Speaker
Description
The super-fast (~day), very-high-energy (VHE; >0.1 TeV) photon flares from the nearby active galactic nucleus M87 provide a unique, exciting opportunity to fast-forward our understanding of particle acceleration in jets. After a long break since 2010, the Event Horizon Telescope (EHT) multiwavelength (MWL) campaign captured a new VHE flare in 2018 with unprecedented frequency coverage including cm/mm-VLBI, EHT, Swift/Chandra/NuSTAR, Fermi-LAT and H.E.S.S./MAGIC/VERITAS. However, the angular resolution at TeV energies cannot resolve the emission region more precisely than within the entire galaxy itself. Also, the causality argument from the short VHE flare duration can only limit the size of the emission region to be small (~10 gravitational radii, $r_g$), leaving the location uncertain from somewhere between the black hole vicinity (few $r_g$) out to the knots ($10^6 r_g$, HST-1). It is thus only the simultaneous MWL facilities, with much smaller angular resolution at other frequencies, that can help narrow down the location and physical nature of the VHE flares. The recent publication of the 2018 EHT MWL data set in 2024 provided only phenomenological 2/3-zone modelling, calling for a more physically grounded interpretation. I will discuss precisely such modelling, with a component of persistent emission from an MHD driven multizone jet in combination with a time-dependent flaring component. Along the way, I will give updates on the new developments of the AM³ software. Looking ahead, this work is also particularly relevant as a preparation for the confirmed 2-month EHT/MWL/VHE movie campaign in Spring 2026, with even better temporal and spectral coverage to finally fully reveal the physics of M87’s super-fast VHE flares.
