Investigating a TeV-Halo Candidate around PSR J1928+1746 with HAWC
We present an updated High-Altitude Water Cherenkov (HAWC) analysis of the crowded Galactic-plane area near PSR J1928+1746, which was previously linked to the extended source 3HWC J1928+178. With 2904 days of HAWC data, improved event reconstruction, and a multicomponent likelihood model that includes six TeV source components and Galactic diffuse emission, we describe the region using six components and find a distinct, moderately extended source close to PSR J1928+1746. This source, HAWC J1928+1750, is detected from about 2 TeV to above 100 TeV and is well-described by a log-parabola spectrum with normalization $K = 5.0 \times 10^{-15}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$ at 12 TeV, index $α= 2.09$, curvature $β= 0.35$, and Gaussian extension $σ= 0.19^\circ$. Interpreting the emission using diffusion-halo templates under the assumption $B = 8 μ\mathrm{G}$ yields the diffusion coefficient D(100 TeV) = $2.1 \times 10^{27}$ cm$^2$ s$^{-1}$, which is about 500 times smaller than typical interstellar diffusion values at similar energies. This suggests that particle transport around PSR J1928+1746 is strongly suppressed under the TeV-halo interpretation. The TeV spectrum is consistent with leptonic inverse-Compton emission originating from pulsar-injected electrons and positrons, which requires less than approximately 1% of the pulsar's characteristic spin-down energy. However, a hadronic contribution from the surrounding environment cannot be excluded.