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

TL;DR

This paper models the multi-wavelength pulse profiles of the millisecond pulsar PSR B1821-24 using a single-pole annular gap model, successfully explaining the origin of different pulse peaks across radio, X-ray, and gamma-ray bands.

Contribution

It introduces a detailed modeling approach that reproduces multi-wavelength pulse profiles of PSR B1821-24, clarifying emission regions and supporting pulsar emission theories.

Findings

Radio peaks originate from different gap regions at varying altitudes.

X-ray and gamma-ray peaks mainly originate from the annular gap region.

Gamma-ray emission from the core gap region influences the first gamma-ray peak.

Abstract

PSR B1821$-$24 is a solitary millisecond pulsar (MSP) which 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 suitable magnetic inclination angle ($\alpha=40^\circ$) and viewing angle ($\zeta=75^\circ$), we managed to reproduce its pulse profiles of three wavebands. It is found that the middle radio peak is originated from the core gap region at high altitudes, and the other two radio peaks are originated from the annular gap region at relatively low altitudes. Two peaks of both X-ray and $\gamma$-ray wavebands are fundamentally originated from 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.