Speaker
Description
HESS J1825−137 is one of the brightest and most extended pulsar wind nebulae in the gamma-ray sky, providing a unique laboratory for investigating particle acceleration and the origin of very-high-energy emission. We present a broadband spectral study of HESS J1825−137 and its environment, combining measurements from Fermi-LAT, H.E.S.S., HAWC, and VERITAS over the energy range from approximately 0.1 GeV to 160 TeV. The spectral energy distribution is interpreted using leptonic, hadronic, and lepto-hadronic emission scenarios within the Naima framework, with model parameters constrained through Markov Chain Monte Carlo sampling.
For the baseline GeV–TeV dataset, model comparison using the Bayesian Information Criterion favors a leptonic interpretation, with an inferred electron energy budget of (W_e = 4.25\times10^{48}) erg, consistent with previous estimates. We then investigate how additional measurements at the highest energies affect the physical interpretation by considering simulated Cherenkov Telescope Array Observatory (CTAO) observations and ultra-high-energy measurements from the Large High Altitude Air Shower Observatory (LHAASO). In both cases, the extended high-energy coverage increases the statistical preference for models containing a hadronic component. The corresponding proton energy budget, (W_p \approx 2.5\times10^{48}) erg, remains compatible with proton–proton interactions in the dense molecular environment surrounding the nebula.
Our results highlight the importance of precise spectral measurements above approximately 10 TeV, where Klein–Nishina suppression progressively reduces the inverse-Compton contribution and enhances the ability to distinguish between leptonic and hadronic emission. HESS J1825−137 therefore represents a particularly promising target for CTAO and current ultra-high-energy gamma-ray observatories to probe the transition between these emission regimes.
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