Model atmospheres and spectra of cooling neutron stars
Abstract
I describe a numerical method for obtaining model atmospheres and spectra of magnetized cooling neutron stars. Self-consistent solutions for the emergent radiation field and constraints of atmospheric structure are derived using the classical technique of complete linearization for the range of effective temperature and magnetic field characteristic of these objects. The presentation is specialized to the dielectric response of fully ionized, vacuum-corrected magnetized hydrogen plasma; the methodology is extensible to admixtures of helium and may be generalized to partially ionized species. Specific model results are examined to demonstrate the polarization content and angular distributions of the radiation field. Auxiliary effects of vacuum resonance are found to generate ion cyclotron line inversion in the spectra of hot neutron stars with intense magnetic fields. These model spectra differ substantially from the blackbody function, and the discrepancies are quantified by the ratio of X-ray temperatures Tbb/ Teff and the optical magnitude displacement. Examples of these effects are discussed with emphasis on the diagnostic properties of the magnetic field, the nature of instrumental efficiencies, and the magnitude of interstellar absorption. An effective displacement rule for uniformly magnetized neutron stars is also recovered. I conclude with the derivation of a pulsar atmosphere model for modulated thermal X-rays from neutron stars, synthesizing the spectral modeling for arbitrary magnetic fields of the present work with non-uniform crustal conductivity assuming the magnetic dipole geometry. I present an analysis of Chandra observations of the middle-aged radio pulsar PSR 0656+14 in the context of this model.
- Publication:
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Ph.D. Thesis
- Pub Date:
- November 2003
- Bibcode:
- 2003PhDT........11L
- Keywords:
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- Physics: Astronomy and Astrophysics