Geminga pulsar halo multi-wavelength SED and X-ray surface brightness. Left panel: Interpretation of all available Geminga pulsar halo multi-wavelength SED data, from the gamma-ray inverse Compton emission (Fermi-LAT, H.E.S.S., HAWC) to the X-ray upper limits (XMM-Newton, NuSTAR) as obtained in this work. The inverse Compton and synchrotron emissions are obtained within a model in which electrons and positron pairs diffuse in a low diffusion zone, see text for details on the model parameters. Right panel: Comparison of the Geminga’s synchrotron halo surface brightness with the XMM-Newton upper limits on the angular profile.