Sgr A* variability
GRMHD and radiative transfer modelling of the Galactic Centre black hole.
UCL / Mullard Space Science Laboratory · 2023 – 2024 · with Dr Ziri Younsi and Prof Kinwah Wu
Sagittarius A* varies across the electromagnetic spectrum on timescales from minutes to hours. What that variability tells us about the accretion flow depends entirely on how the electrons are heated — and that is precisely the part of the physics that GRMHD does not determine on its own.
Method. General-relativistic magnetohydrodynamic simulations run in BHAC, post-processed through general-relativistic radiative transfer in BHOSS, in Fortran and Python.
Parameter space. Magnetically arrested disc states across black hole spins \(a = -0.94\) to \(+0.94\), with three competing electron-heating prescriptions: R–\(\beta\), turbulent heating, and magnetic reconnection.
Status. Manuscript in preparation, targeting MNRAS, with co-authors including Dr Yosuke Mizuno and Dr Christian M. Fromm. Discussions with researchers from the EHT (Event Horizon Telescope) collaboration informed the radiative-transfer setup.