Speaker
Description
Recently, the HAWC experiment revealed an extended multi-TeV emission (so-called TeV halo) around several tens of parsecs around Geminga, implying an inefficient diffusion zone in that region. On the other hand, the TeV-emitting electrons are supposed to give rise to X-ray as well via synchrotron radiation in the ISM magnetic field. We perform a X-ray analysis on the region around Geminga but did not detect significant X-ray signal. This result translates to an upper limit of of $1\mu$G for the magnetic field in the TeV halo. Either the small diffusion coefficient or the weak magnetic field is quite puzzling in the context of isotropic particle diffusion. We propose that both X-ray and TeV observations can be explained in the context of anisotropic diffusion without invoking extreme parameters for the surrounding ISM.
