High-Energy Properties of Pulsed Emission from Millisecond Pulsars
Abstract
We make a modification of our previous outer gap model of high-energy emission from millisecond pulsars (MSPs) by taking the effects of the magnetic inclination angles and magnetic geometry into account. In the revised version of our outer gap model, a strong multipole magnetic field exists near the stellar surface, and the X-rays are produced by the backflow current of the outer gap and consist of one power-law and two thermal components. These X-rays collide with high-energy photons inside the outer gap to sustain the outer gap, and then high-energy γ-rays are produced in the outer gap. The fractional size of the outer gap is a function of the radial distance to the neutron star and the magnetic inclination angle for a given millisecond pulsar. We have applied this model to account for the pulsed X-ray emission from the MSPs outside of and in the globular cluster 47 Tuc, and our results indicate that the relation between the pulsed component of X-ray luminosity (LtheoX,pul) and the pulsar spin-down power (Lsd) satisfies LtheoX,pul~L1.17+/-0.10sd for the MSPs outside of 47 Tuc and LtheoX,pul~L0.58+/-0.06sd for the MSPs in 47 Tuc, which is consistent with the relation between the observed pulsed component of X-ray luminosity (LobsX,pul) and Lsd: LobsX,pul~L1.12+/-0.10sd for the MSPs outside of 47 Tuc and LobsX,pul~L0.24+/-0.43sd for the MSPs in 47 Tuc. We also applied our model to predict the averaged high-energy γ-ray fluxes and to compare them with the sensitivity of AGILE and GLAST.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2007
- DOI:
- 10.1086/520490
- Bibcode:
- 2007ApJ...666.1165Z
- Keywords:
-
- Gamma Rays: Theory;
- Stars: Pulsars: General;
- Radiation Mechanisms: Nonthermal;
- Radiation Mechanisms: Thermal;
- Stars: Neutron;
- X-Rays: General