Time-dependent leptonic modeling of four LHAASO sources: Ultra-high-energy emission from mature pulsar wind nebulae

Whether pulsar wind nebulae (PWNe) in relatively late evolutionary stages can sustain ultra-high-energy (UHE) γ-ray emission remains an open question. In this paper, we investigate this issue by modeling four LHAASO sources associated with pulsar-powered sys- tems — namely 1LHAASO J0007+7303u, 1LHAASO J1857+0245, 1LHAASO J1849-0002, and 1LHAASO J1740+0948 — using a time-dependent one-zone leptonic model. The multi- wavelength spectral energy distributions (SEDs) of these sources are consistently reproduced within a unified framework, where the emission above 100 TeV is primarily attributed to in- verse Compton scattering of multi-hundred-TeV electrons. Model parameters are constrained via MCMC sampling for the first three sources, while the parameter space is explored directly for 1LHAASO J1740+0948. The inferred present-day magnetic field strengths range from 2.47 to 5.87 μG, comparable to typical interstellar values. Our results suggest that PWNe can remain detectable above 100 TeV even at relatively late evolutionary stages, supporting pulsar-powered systems as viable counterparts of Galactic UHE γ-ray sources