Modeling Multi-wavelength Pulse Profiles of Millisecond Pulsar PSR B1821-24

PSR B1821-24 is a solitary millisecond pulsar that radiates multi-wavelength pulsed photons. It has complex radio, X-ray, and gamma-ray pulse profiles with distinct peak phase separations that challenge the traditional caustic emission models. Using the single-pole annular gap model with a suitable magnetic inclination angle (alpha = 40 degrees) and viewing angle (zeta = 75 degrees), we managed to reproduce its pulse profiles of three wavebands. It is found that the middle radio peak originated from the core gap region at high altitudes, and the other two radio peaks originated from the annular gap region at relatively low altitudes. Two peaks of both X-ray and gamma-ray wavebands basically originated from the annular gap region, while the gamma-ray emission generated from the core gap region contributes somewhat to the first gamma-ray peak. Precisely reproducing the multi-wavelength pulse profiles of PSR B1821-24 enables us to understand emission regions of distinct wavebands and justify pulsar emission models.