Localisation of the non-thermal X-ray emission of PSR~J2229+6114 from its multi-wavelength pulse profiles

This is the authors' abstract. We don't add key points for this paper.

Pulsars are detected over the whole electromagnetic spectrum, from radio wavelengths up to very high energies, in the GeV-TeV range. Whereas the radio emission site for young pulsars is well constrained to occur at altitudes about several percent of the light-cylinder radius and γ-ray emission is believed to be produced in the striped wind, outside the light-cylinder, their non-thermal X-ray production site remains unknown. The aim of this letter is to localize the non-thermal X-ray emission region based on multi-wavelength pulse profile fitting for PSR J2229+6114, a particularly good candidate due to its high X-ray brightness. Based on the geometry deduced from the joint radio and γ-ray pulse profiles, we fix the magnetic axis inclination angle and the line of sight inclination angle but we leave the region of X-ray emission unlocalised, somewhere between the surface and the light-cylinder. We localize this region and its extension by fitting the X-ray pulse profile as observed by the NICER, NuSTAR and RXTE telescopes in the ranges 2-7 keV, 3-10 keV and 9.4-22.4 keV, respectively. We constrain the non-thermal X-ray emission to arise from altitudes between 0.2\,rL and 0.55\,rL where rL is the light cylinder radius. The magnetic obliquity is approximately α ≈ 45-50 and the line of sight inclination angle ζ ≈ 32-48. This letter is among the first works to tightly constrain the location of the non-thermal X-ray emission from pulsars. We plan to apply this procedure to several other good candidates to confirm this new result.