X-Ray Studies of HESS J1809-193 with Suzaku

Abstract

Suzaku observed the region including HESS J1809-193, a TeV unidentified source, and confirmed the existence of extended hard X-ray emission previously reported by ASCA, as well as hard X-ray emission from PSR J1809-1917 in this region. A one-dimensional profile of the diffuse emission is represented along with a Gaussian model with a best-fit σ of 7'±1'. The diffuse emission extends for at least 21 pc (at the 3σ level, assuming a distance of 3.5 kpc), and has a hard spectrum with a photon index of Γ ∼ 1.7. The hard spectrum suggests a pulsar wind nebula 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 the spatial variation of the energy spectrum, but no systematic spectral change in the extended emission was found. These results imply that the X-ray emitting pulsar wind electrons can travel up to 21 pc from the pulsar without any noticeable energy loss via synchrotron emission.