X-Ray Studies of PSR J1838–0655 and its Wind Nebula Associated with HESS J1837–069 and 1LHAASO J1837–0654u

We analyzed X-ray data from Chandra, XMM-Newton, NICER, and NuSTAR to characterize the properties of the pulsar PSR J1838−0655 and its pulsar wind nebula (PWN) associated with HESS J1837−069. Based on 5.5 yr of NICER monitoring, we detected a glitch around MJD 59300, characterized by a fractional frequency jump of approximately 2 × 10 −6 . We constructed semi-phase-coherent timing solutions for pre- and postglitch epochs, allowing for phase alignment of multi-instrument data and a subsequent measurement of the pulsed spectrum of the pulsar. This analysis confirmed previously reported spectral curvature and revealed a peak energy of 7 3 − 26 + 85 keV in the pulsar’s spectral energy distribution (SED), based on a logpar model fit of the pulsed spectrum. We discuss these findings within the framework of pulsar magnetospheric emission scenarios. The PWN’s X-ray spectrum is well described by a power law with a photon index of 2.1 ± 0.3, softer than previously reported measurements. We also characterized the X-ray emission from another extended X-ray source AX J1837.3−0652 within the extent of HESS J1837−069. Based on the spatial and spectral properties of these X-ray sources, we propose a leptonic emission scenario for HESS J1837−069 and demonstrate its feasibility through SED modeling. Finally, we discuss the implications of our model results and alternative scenarios for the gamma-ray emission.