2026ApJ...997..324N

Extended very-high-energy γ-ray emission from middle-aged pulsars as revealed recently by several ground-based γ-ray experiments has strong implication on the transport of high-energy particles in the interstellar medium surrounding those pulsars. The γ-ray emission is widely believed to be produced by high-energy electrons and positrons accelerated by the pulsar wind nebulae when scattering off the interstellar radiation field via the inverse Compton process. Consequently, multiwavelength counterparts of the γ-ray halos are expected to be present, which have not yet been detected. In this work we report the possible detection of extended X-ray emission from a ∼0$\mathop{.}\limits^{\unicode{x000b0}}$2 radius region around PSR B0656+14 with eROSITA. In spite of there being uncertainties of the on-orbit point-spread function of the pointing mode, the radial profile of PSR B0656+14 is found to be broader than that of a star at similar observational conditions, indicating that emission is possibly from the expected extended halo around the pulsar. The spectrum of the emission can be described by a power-law function with an index of ∼3.7. Its surface brightness declines with radius faster than the prediction of the particle diffusion and synchrotron radiation in a uniform magnetic field, suggesting the existence of a radial gradient of the magnetic field strength as ∼r^–1. The magnetic field strength in the X-ray-emitting region is constrained to be 4-10 μG.