Self-consistent interpretations of the multiwavelength gamma-ray spectrum of LHAASO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">J</mml:mi><mml:mn>0621</mml:mn><mml:mo>+</mml:mo><mml:mn>3755</mml:mn></mml:mrow></mml:math>
Kun Fang, Shao-Qiang Xi, Xiao-Jun Bi
Abstract
LHAASO $\mathrm{J}0621+3755$ is a TeV gamma-ray halo newly identified by LHAASO-KM2A. It is likely to be generated by electrons trapped in a slow-diffusion zone around PSR $\mathrm{J}0622+3749$ through inverse Compton scattering. However, when the gamma-ray spectrum of LHAASO-KM2A is fitted, the GeV fluxes derived by the commonly used one-zone normal diffusion model for electron propagation are significantly higher than the upper limits of Fermi-LAT. In this work, we try to solve the contradiction by adopting a more generalized propagation model, i.e., the superdiffusion model or the two-zone diffusion model. For the superdiffusion scenario, we find that a model with superdiffusion index $\ensuremath{\alpha}\ensuremath{\lesssim}1.2$ can meet the constraints of Fermi-LAT observation. For the two-zone diffusion scenario, the size of the slow-diffusion zone is required to be smaller than $\ensuremath{\sim}50\text{ }\text{ }\mathrm{pc}$, which is consistent with theoretical expectations. Future precise measurements of the Geminga halo may further distinguish between these two scenarios for the electron propagation in pulsar halos.