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Full-Text Articles in Physical Sciences and Mathematics
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. C. Brown, J. P. Cassinelli, Q. Li, A. F. Kholtygin, R. Ignace
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. C. Brown, J. P. Cassinelli, Q. Li, A. F. Kholtygin, R. Ignace
Richard Ignace
The hot star wind momentum problem eta = M-upsiloninfinity/(L/c) much greater than 1 is revisited, and it is shown that the conventional belief, that it can be solved by a combination of clumping of the wind and multiple scattering of photons, is not self-consistent for optically thick clumps. Clumping does reduce the mass loss rate. M, and hence the momentum supply, required to generate a specified radio emission measure epsilon, while multiple scattering increases the delivery of momentum from a specified stellar luminosity L. However, in the case of thick clumps, when combined the two effects act in opposition rather …
Free-Free Spectral Energy Distributions Of Hierarchically Clumped Hii Regions., Richard Ignace, Ed Churchwell
Free-Free Spectral Energy Distributions Of Hierarchically Clumped Hii Regions., Richard Ignace, Ed Churchwell
Richard Ignace
In an effort to understand unusual power-law spectral slopes observed in some hypercompact HII regions, we consider the radio continuum energy distribution from an ensemble of spherical clumps. An analytic expression for the free-free emission from a single spherical clump is derived. The radio continuum slope (with F_\nu \nu^\alpha) is governed by the population of clump optical depths N(tau), such that (a) at frequencies where all clumps are thick, a continuum slope of +2 is found, (b) at frequencies where all clumps are optically thin, a flattened slope of -0.11 is found, and (c) at intermediate frequencies, a power-law segment …
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Iv. Application To Polarized P Cygni Wind Lines., R. Ignace, K. H. Nordsieck, J. P. Cassinelli
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Iv. Application To Polarized P Cygni Wind Lines., R. Ignace, K. H. Nordsieck, J. P. Cassinelli
Richard Ignace
The Hanle effect has been proposed as a new diagnostic of circumstellar magnetic fields for early-type stars, for which it is sensitive to field strengths in the 1-300 G range. In this paper we compute the polarized P-Cygni line profiles that result from the Hanle effect. For modeling the polarization, we employ a variant of the ``last scattering approximation''. For cases in which the Sobolev optical depths are greater than unity, the emergent line intensity is assumed to be unpolarized; while for smaller optical depths, the Stokes source functions for the Hanle effect with optically thin line scattering are used. …