We examine two separate scenarios, both occurring in the magnetospheres of strongly magnetized neutron stars, which result in the generation of gamma -rays via the inverse Compton scattering of soft photons by relativistic electrons. First, we test the idea that pulsars (isolated and rapidly rotating neutron stars) have accretion disks around them. In this scenario, charged particles which are electrostatically accelerated to highly relativistic energies interact (via inverse Compton scattering) with the radiation field emitted from the disk. We calculate the particle dynamics, and use a Monte Carlo technique to determine the upscattered radiation spectrum. We find that for hot disks, the electrons can experience severe retardation, with most of the energy (~ 99%) then being converted into gamma -rays. When applied to specific pulsars, we find that this scenario does not contradict the circumstellar disk model. Second, we develop a model for gamma-ray bursts. Although both the issues of energy release and gamma-ray emission from relativistic particles interacting with soft photons have been discussed in the context of these transient events, the question of how the released energy is transferred to the particles has not been resolved. In response to this, we examine a scenario where Alfven waves with spatially sheared magnetic field components are generated on the stellar surface by an energized crust (e.g., a starquake). We show that in a resistive medium, these waves are natural particle accelerators when the dominant dissipative process is due to the annihilation of the sheared field lines. We solve the dynamics for electrons which are accelerated from the stellar surface by these waves and subsequently scatter with thermal photons emitted by the energized stellar region. We find that this model reproduces a typical gamma -ray burst spectrum for reasonable physical parameters. Finally, we consider the importance of the effects due to quantization and field instabilities to our results, and discuss the future direction of these issues.
- Pub Date:
- NEUTRON STARS;
- Physics: Astronomy and Astrophysics