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Resonance Line Scattering Polarization In Optically Thin Planar Equatorial Disks., Richard Ignace
Resonance Line Scattering Polarization In Optically Thin Planar Equatorial Disks., Richard Ignace
Richard Ignace
This paper is the third in a series on the anisotropic scattering by optically thin resonance lines in extended stellar envelopes. Considered here is the polarization arising from resonance line scattering in equatorial disks. The shape of the polarized line profile is analytically derived under simplifying conditions of constant expansion or rotation for thin lines, with stellar occultation and finite star depolarization effects also included. The polarized profiles for the two cases are radically different. Moreover owing to the symmetries, rotation leads to profiles in both Qν and Uν, whereas only a Qν profile survives for …
Exospheric Models For The X-Ray Emission From Single Wolf-Rayet Stars., R. Ignace, L. M. Oskinova
Exospheric Models For The X-Ray Emission From Single Wolf-Rayet Stars., R. Ignace, L. M. Oskinova
Richard Ignace
We review existing ROSAT detections of single Galactic Wolf-Rayet (WR) stars and develop wind models to interpret the X-ray emission. The ROSAT data, consisting of bandpass detections from the ROSAT All-Sky Survey (RASS) and some pointed observations, exhibit no correlations of the WR X-ray luminosity (LX) with any star or wind parameters of interest (e.g. bolometric luminosity, mass-loss rate or wind kinetic energy), although the dispersion in the measurements is quite large. The lack of correlation between X-ray luminosity and wind parameters among the WR stars is unlike that of their progenitors, the O stars, which show …
Analytic Inversion Of Emission Lines Of Arbitrary Optical Depth For The Structure Of Supernova Ejecta., R. Ignace, M. A. Hendry
Analytic Inversion Of Emission Lines Of Arbitrary Optical Depth For The Structure Of Supernova Ejecta., R. Ignace, M. A. Hendry
Richard Ignace
We derive a method for inverting emission line profiles formed in supernova ejecta. The derivation assumes spherical symmetry and homologous expansion (i.e., v(r)∝r), is analytic, and even takes account of occultation by a pseudo-photosphere. Previous inversion methods have been developed which are restricted to optically thin lines, but the particular case of homologous expansion permits an analytic result for lines of arbitrary optical depth. In fact, we show that the quantity that is generically retrieved is the run of line intensity Iλ with radius in the ejecta. This result is quite general, and so could be applied to resonance lines, …
Hot Star Polarimetric Variability And The Nature Of Wind Inhomogeneities., J. C. Brown, R. Ignace, J. P. Cassinelli
Hot Star Polarimetric Variability And The Nature Of Wind Inhomogeneities., J. C. Brown, R. Ignace, J. P. Cassinelli
Richard Ignace
The problem is addressed of how much hot star polarisation variability can result from density redistribution processes within the wind as opposed to localised enhancement of stellar mass loss rate, such as ejections of wind inhomogeneities. For optically thin electron scattering, we present a theory for the relative polarisation arising from particle redistribution and consider several specific cases relevant to interpreting observations of wind variability. It is concluded that, allowing for partial cancellation of the contribution from compressed and evacuated regions, density redistribution internal to the wind can produce significant polarisation but only for processes that redistribute wind material over …
Wolf-Rayet Wind Structure And Optical Variability., Q. Li, J. C. Brown, R. Ignace, J. P. Cassinelli, L. M. Oskinova
Wolf-Rayet Wind Structure And Optical Variability., Q. Li, J. C. Brown, R. Ignace, J. P. Cassinelli, L. M. Oskinova
Richard Ignace
Results are presented on the expected variability of Wolf-Rayet (WR) stars in broad-band optical polarimetry and photometry, and in emission line profiles, due to an inhomogeneous random distribution of blobs in spherical geometry. Time dependent 3-D simulations are carried out with blob ejection random in time and direction, and the radiation properties are evaluated in the optically thin limit. In contrast with previous purely statistical analyses, inclusion in the present treatment of a beta velocity law and stellar occultation effects can yield results consistent with observations of the mean polarisation bar p and the ratio R=sigma_p /sigma_phot of polarimetric to …