X-Ray Studies of HESS J1809-193 with Suzaku

Suzaku observed the region including HESS J1809-193, one of the TeV unidentified (unID) sources, and confirmed existence of the extended hard X-ray emission previously reported by ASCA, as well as hard X-ray emission from the pulsar PSR J1809-1917 in the region. One-dimensional profile of the diffuse emission is represented with a Gaussian model with the best-fit sigma of 7+-1 arcmin. The diffuse emission extends for at least 21 pc (at the 3sigma level, assuming the distance of 3.5 kpc), and has a hard spectrum with the photon index of Gamma ~1.7. The hard spectrum suggests the pulsar wind nebula (PWN) origin, which is also strengthened by the hard X-ray emission from PSR J1809-1917 itself. Thanks to the low background of Suzaku XIS, we were able to investigate spatial variation of the energy spectrum, but no systematic spectral change in the extended emission is found. These results imply that the X-ray emitting pulsar wind electrons can travel up to 21 pc from the pulsar without noticeable energy loss via synchrotron emission.