X-ray Signatures of Particle Escape from Pulsar Wind Nebulae

[eng] This PhD thesis aims at understanding the particle escape and subsequent emission processes taking place in Bow-shock Pulsar Wind Nebulae (BSPWNe), trying to connect a) the observational findings of large X-ray jet-like structures resolved in some of these systems; b) the phenomenology associated to the recently discovered gamma-ray TeV halos, and c) the prediction of similar extended structures in the radio band. To this end, I have studied in detail three BSPWN with prominent extended emission features detected in X-rays showing evidences of such particle escape mechanism. For the first source, PWN J1135-6055, archival Chandra observations have revealed a compact nebula as well as two lateral jet-like structures displaying a highly asymmetric geometry. The origin of these structures is discussed in different scenarios, either considering the development of ”kinetic jets” from particle escape processes, or the presence of ”true pulsar jets” bent by the external medium pressure. The properties of PSR J1135-6055 are reminiscent of those of the Geminga PWN, one of the few BSPWN with a confirmed TeV halo structure. For the second source, PWN B1853+01 located inside SNR W44, a rich X-ray data set composed of archival data from Chandra, XMM-Newton and NuSTAR is analysed. The results reveal the presence of a cometary tail trailing the pulsar, a spectrally hard antennae-like feature ahead of the pulsar, as well as a possible ”X-ray Halo” around the PWN. These findings are discussed and compared with the PWN in G327.1-1.1, known to display also both antennaeand halo-like extended emission in X-rays. PWN in G327.1-1.1 is also known to have a TeV counterpart. For the third source, IGR J11014-6103 (the ”Lighthouse Nebula”), the possibility to detect extended radio emission produced by the particle population powering the jet-like structures detected in X-rays is investigated. If relativistic particles with moderate Lorentz factors, γ ≳ 105, are able to escape the bowshock region, such extended ”Radio Halo”-like structures could be detected with current instruments. This study provides therefore an observational test allowing to constrain the escape mechanism thought to operate in BSPWNe. The results of this thesis provide new constraints on the particle escape mechanism( s) operating in BSPWNe, and argue for a common mechanism leading to the extended features around BSPWNe observed in the X-ray and gamma-ray energy band, and potentially detectable also at radio energies.