086188

2HWC J1928+177 is a bright Galactic gamma-ray source detected up to 100 TeV. It is a peculiar HAWC source comma as VERITAS and HESS failed to detect its gamma-ray emission and there is no SNR or PWN nearby. At the HAWC source position comma there is a variable X-ray source comma potentially associated with a bright IR source. The non-thermal X-ray spectrum and the lack of aperiodic variability indicate that it is a TeV gamma-ray binary. XMM will determine the nature of the X-ray counterpart candidate comma constrain its X-ray variability pattern for future TeV observations and search for other X-ray sources. If the X-ray counterpart candidate is not a TeV gamma-ray binary and no diffuse X-ray emission is found comma the HAWC source would be the most remarkable dark accelerator with no counterpart below 10 TeV.