Poster Abstract

P.9 Jesse Vos (Radboud University)

Simulated variability and time-lags of Sgr A*

The supermassive black hole at the center of our galaxy, Sgr A*, displays a flat radio spectrum that is associated with the presence of a jet. Flares produced by the jet originate in the jet base and will propagate outwards over time. Observationally, they occur for higher frequencies first and will gradually move to lower frequency bands, due to cooling and magnetic dissipation effects, as the flare moves further outwards. This phenomenon is known as a time-lag. We evaluate the matter in the direct vicinity of the black hole by performing six general-relativistic magnetohydrodynamical (GRMHD) simulations that vary in black hole spin and magnetic field description. For most models, we recover the predicted linearity between observing wavelength and time-lag from the synthetic lightcurves. Although the time-lag profiles consistently underestimate their observational counterpart, they fall within the observational uncertainty and correspond to an outflow velocity of γβ ≈ 2 (v ≈ 0.89c).