Physics
Scientific paper
Aug 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995stan.reptr....r&link_type=abstract
Technical Report, Stanford Univ. CA United States Dept. of Physics.
Physics
Neutron Stars, Stellar Radiation, Gamma Rays, X Rays, Stellar Atmospheres, Stellar Models, Spectral Emission, Pulsars, Pair Production, Inverse Scattering, Polarization Characteristics
Scientific paper
The proposed goal of this High Energy Theory/Data Analysis Program grant was the study of neutron stars' emission in X-rays and gamma-rays and their resulting appearance as galactic source populations. In one of the main efforts of this proposal, substantial progress was made on the development of a new model for the emission of gamma-rays from isolated rotation-powered pulsars. In phase 1 of the work we showed how a modified version of the 'outer gap' model of pulsar emission could reproduce the double peaked profiles seen in CGRO pulsar observations. This work also demonstrated that the spectrum of gap radiation varies significantly with position in the magnetosphere, and produced approximate computations of the emission from outer magnetosphere gap zones, including primary curvature radiation, gamma-gamma pair production, and synchrotron radiation and inverse Compton scattering by the resulting secondary particles. One main conclusion was that the original Cheng, Ho and Ruderman (1986) picture of outer magnetosphere radiation physics could not reproduce the fluxes seen from newly observed gamma-ray pulsars. Other work on the high energy pulsar emission examined the possibility of MeV-GeV polarization measurements and has developed a new picture of radiation physics and particle acceleration in neutron star magnetospheres. This scheme of radiation in the outer magnetosphere has now been sufficiently developed to provide a substantial new model for pulsar emissions above the radio band. A second major thrust of the neutron star modeling efforts has been a new theoretical study of neutron star atmospheres and models of their thermal surface emission. In Romani et. al. (1995) we reported on a series of model atmospheres based on new opacity data from the OPAL group. A complete description of this new family of models for low field neutron stars with various surface compositions was reported in Rajagopal and Romani (1995). There we also compared our results with X-ray observations of the millisecond pulsar J0437-4715; this work has afforded the first observational constraints on the chemical composition of the neutron star surface. During this proposal there have also been studies of BH LMXB populations, the evolution of neutron star magnetic fields, and the properties of pulsar shock waves and other plerionic emission.
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