Other
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt........40d&link_type=abstract
PhD Thesis North Carolina State University
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1
Supernova Remnants, Radiation Mechanisms: Nonthermal, Acceleration Of Particles, Shock Waves, Cosmic Rays
Scientific paper
Supernova remnants present an excellent opportunity to study the shock acceleration of relativistic particles. X-ray synchrotron emission from relativistic electrons should contain important information, but extracting it requires advances in models and observations. I present the first test of sophisticated synchrotron models against high resolution observations on SN 1006, the first and best example of synchrotron X-ray emission, which has been well observed at radio, X-ray and gamma-ray wavelengths. Synchrotron emission can be limited at the highest energies by finite age, radiative losses or electron escape. Earlier calculations suggested that SN 1006 was escape limited. I adapted an escape-limited synchrotron model for XSPEC, and demonstrated that it can account for the dominantly nonthermal integrated spectrum of SN 1006 observed by ASCA-GIS and RXTE while constraining the values of the maximum electron energy and other parameters. Combined with TeV observations, th! e fits give a mean postshock magnetic field strength of 9 microgauss and 0.7% of the supernova energy in relativistic electrons. Simultaneous thermal fits gave abundances far above solar, as might be expected for ejecta but had not previously been observed. I created subsets of the escape-limited model to fit spatially resolved ASCA SIS observations. I found only small differences between the northeast and southwest limbs. A limit of less than 9% was placed on the amount of nonthermal flux elsewhere in the remnant. Important findings include the possibility that rolloff frequency may change across the remnant face, and ruling out cylindrical symmetry for SN 1006 along a NW/SE axis. These models have implications far beyond SN 1006. The only previous model available to describe X-ray synchrotron emission was a powerlaw. These new models are superior to powerlaws both for their robust constraints and because they shed physical insight on the acceleration mechanism. As new inst! ruments increase our spatial and spectral resolution I predic! t many more remnants will be found with varying amounts of X-ray synchrotron emission, hidden along with thermal lines and continuum. The ability to separate thermal and nonthermal emission is essential to understanding both nonthermal emission as well as the thermal component.
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