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Full-Text Articles in Stars, Interstellar Medium and the Galaxy
An Explanation Of Observed Trends In The X-Ray Emission From Single Wolf-Rayet Stars., R. Ignace, L. M. Oskinova
An Explanation Of Observed Trends In The X-Ray Emission From Single Wolf-Rayet Stars., R. Ignace, L. M. Oskinova
Richard Ignace
The O and early B star winds show empirical correlations between X-ray (L_x) and Bolometric (L_Bol) luminosity as well as wind properties such as wind momentum and wind kinetic energy. Wolf-Rayet stars do not. We discuss scaling relations to qualitatively explain this lack of correlation among the WR winds and to quantitatively reproduce the observed ratio of X-ray luminosities between the N-rich WN types and C-rich WC types. If (a) the filling factor of hot X-ray emitting gas varies as (M⊙/v_\infty)(-1) for stars of different mass loss and terminal speed and (b) the ambient Wolf-Rayet wind component is optically thick …
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Ii. Some Theoretical Results For Resolved Line Profiles., R. Ignace, J. P. Cassinelli, K. H. Nordsieck
The Hanle Effect As A Diagnostic Of Magnetic Fields In Stellar Envelopes Ii. Some Theoretical Results For Resolved Line Profiles., R. Ignace, J. P. Cassinelli, K. H. Nordsieck
Richard Ignace
A magnetic field diagnostic of stellar winds that uses the Hanle effect is discussed. This diagnostic pertains to the modification of resonance-line-scattering polarization in the presence of magnetic fields. The case for resolved polarized profiles of optically thin emission lines is considered, and some analytic results for an expanding equatorial disk are derived. Numerical results for a dipole magnetic field embedded in a spherical outflow are also presented. Although the considerations are somewhat simplified, the primary conclusion is that the modification or creation of line profile polarization by the Hanle effect can be used to discriminate between different magnetic field …
Scattering Polarization Due To Light Source Anisotropy I. Large Spherical Envelope., M. B. Al-Malki, J. F. L. Simmons, R. Ignace, J. C. Brown, D. Clarke
Scattering Polarization Due To Light Source Anisotropy I. Large Spherical Envelope., M. B. Al-Malki, J. F. L. Simmons, R. Ignace, J. C. Brown, D. Clarke
Richard Ignace
Expressions are developed for the flux and polarization of radiation scattered by a spherically symmetric envelope for a central point stellar light source that radiates anisotropically. These are obtained in terms of the components of the spherical harmonics of the flux anisotropy from the source. Such anisotropy can arise from stellar spots, or from distortion of the star through rotation, pulsation, or magnetic effects. Explicit expressions for the Stokes parameters are obtained in the case of an ellipsoidal star of uniform surface brightness. It is thus shown that even when the scattering envelope is spherical, observationally significant polarization can arise …
Microlensing Of Circumstellar Envelopes I. Simplified Considerations For Diagnosing Radial And Azimuthal Flow., R. Ignace, M. A. Hendry
Microlensing Of Circumstellar Envelopes I. Simplified Considerations For Diagnosing Radial And Azimuthal Flow., R. Ignace, M. A. Hendry
Richard Ignace
This paper presents first results on the line profile shapes from a circumstellar envelope in bulk motion as modified by a microlensing event. Only geometrically and optically thin spherical shells in uniform expansion or rotation are considered here so as to emphasise the information content available in the profile shapes. In particular it is demonstrated that for the case of expansion, the line emission can increase by significant factors and the time variation of the profile shape is symmetric about line centre. For uniform rotation the line emission also increases significantly, but the time evolution of the profile shape is …