Exact solution for the hypergeometric Green's function describing spectral formation in x-ray pulsars
- Center for Earth Observing and Space Research, School of Computational Sciences, George Mason University, Fairfax, Virginia 22030-4444 (United States)
An eigenfunction expansion method involving hypergeometric functions is used to solve the partial differential equation governing the transport of radiation in an x-ray pulsar accretion column containing a radiative shock. The procedure yields the exact solution for the Green's function, which describes the scattering of monochromatic radiation injected into the column from a source located near the surface of the star. Collisions between the injected photons and the infalling electrons cause the radiation to gain energy as it diffuses through the gas and gradually escapes by passing through the walls of the column. The presence of the shock enhances the energization of the radiation and creates a power-law spectrum at high energies, which is typical for a Fermi process. The analytical solution for the Green's function provides important physical insight into the spectral formation process in x-ray pulsars, and it also has direct relevance for the interpretation of spectral data for these sources. Additional interesting mathematical aspects of the problem include the establishment of a closed-form expression for the quadratic normalization integrals of the orthogonal eigenfunctions, and the derivation of a new summation formula involving products of hypergeometric functions. By taking various limits of the general expressions, we also develop new linear and bilinear generating functions for the Jacobi polynomials.
- OSTI ID:
- 20699184
- Journal Information:
- Journal of Mathematical Physics, Vol. 46, Issue 5; Other Information: DOI: 10.1063/1.1894965; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-2488
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
ANALYTICAL SOLUTION
BINARY STARS
COSMIC X-RAY SOURCES
EIGENFUNCTIONS
ELECTRONS
EXACT SOLUTIONS
GEOMETRY
GREEN FUNCTION
HYPERGEOMETRIC FUNCTIONS
INTEGRALS
MONOCHROMATIC RADIATION
PARTIAL DIFFERENTIAL EQUATIONS
PHOTON-ELECTRON INTERACTIONS
PHOTONS
POLYNOMIALS
PULSARS