Hope College Physics Department
Research Experiences for Undergraduates
Summer 2012
Project Summary


Project Title: Inverse Compton Upscattering in High-Field Pulsars and Magnetars
Student Name: Matthew Eiles
Student's Home Institution: Hope College
Research Advisor: Dr. Peter Gonthier
Source of Support:

This material is based upon work generously supported by the National Science Foundation under NSF-RUI-AST Grant No. 1009731, by the Michigan Space Grant Consortium, by Hope College Physics Department funds, and by Physics Department endowed funds (specifically the Frissel Fund).

Pulsars with remarkably high magnetic fields, known as magnetars, are a fascinating arena for study in astrophysics. The extreme conditions present in and around them make them distant laboratories for physics experiments unlike any others in the universe. Photon spectra recently detected by the X-ray telescopes RXTE and INTEGRAL indicate that these neutron stars emit radiation with much higher energies in the upper limits than expected based on current models. Resonant Compton upscattering, a quantum-electrodynamical process, is believed to be a leading emission mechanism of high field pulsars and magnetars in this production of intense thermal X-ray radiation. Magnetospheric conditions tend to inject electrons with highly relativistic Lorentz factors, and so the primary focus of the literature has been to study the specific case of ultra-relativistic ground-state to ground-state scattering, where the photon angle relative to the magnetic field prior to scattering is Lorentz-contracted to zero. This specific scattering condition facilitates analytic developments, particularly in the resonant regime. However, inverse Compton scattering can cool electrons down to mildly-relativistic energies, necessitating the development of the more general case where scattering can occur at arbitrary incoming photon angles. Analytic simplifications such as have been done for the relativistic case have yet to be attempted for this more general case, leaving ample space for further research in this area. Opening the scattering angle up to arbitrary angles allows the intermediate state to be excited to arbitrary Landau levels, introducing further difficulties in evaluating the cross section due to the large number of contributing cyclotron decay widths, which now need to be summed over all possible states. This effort requires new analytic developments to handle this full case. We present various preliminary results.

Publications and Presentations: