Search for Pulsar Wind Nebula Associations of Unidentified TeV γ−Ray Sources

Many of the recently discovered galactic very high-energy γ−ray sources are associated with pulsar wind nebulae, which represent the most populous galactic source class at TeV energies. In addition, H.E.S.S. detector discovered in the galactic plane survey a representative population of unidentified TeV γ−ray sources. For a number of these sources a pulsar is an evident association, which is often located within an extended region of the TeV γ−ray emission. These particular H.E.S.S. sources are promising candidates for yet not resolved pulsar wind nebulae. Here we have undertaken a systematic search for X-ray counterparts, using the archival Chandra data, within the extension bounds of the unidentified H.E.S.S. sources, in particular those associated with young, energetic pulsars. A number of X-ray sources have been detected in corresponding Chandra fields. Two of them, CXOU J161729.3-505512 and CXOU J170252.4-412848, are of a special interest because of their exact positional coincidence with the pulsars PSR J1617-5055 and PSR J1702-4128, respectively. All of the detected sources are consistent with being point sources of X-ray emission. The analysis of the archival Chandra data for another young energetic pulsar PSR J1913+1011, associated with the newly discovered TeV γ−ray source HESS J1912+101, does not reveal any statistically significant excess around the pulsar position. No evident X-ray emission can be seen at the center of gravity of HESS J1912+101 either. The corresponding flux upper limits are given. We discuss the implications of these results. Subject headings: binaries: acceleration of particles — gamma rays: theory — pulsars: individual(PSR J1617-5055, PSR J1702-4128, PSR J1913+1011) — Xrays: general Email: [email protected], [email protected], [email protected]