Radiative transfer of ionizing radiation through gas and dust: the stellar source case

A recent comparison of the photoionization models generated by five independent codes run with the same density and stellar radiation shows substantial agreement. Problems are more likely to arise with the defining parameters: the density distribution should be based on observed images, and the ionizing radiation should be from model atmosphere calculations, which, however, are inadequate for stars with winds. Models can be improved by including dust and by incorporating, self-consistently, radiative transfer in optically thick lines. Future work may extend modeling to axially-symmetric objects, to the interface with the hot, shocked, stellar wind, and to the molecular component present around many nebulae.

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Resolving the dusty torus and the mystery surrounding LMC red supergiant WOH G64

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308028858 ◽

2008 ◽

Vol 4 (S256) ◽

pp. 454-458

Author(s):

Keiichi Ohnaka ◽

Thomas Driebe ◽

Karl-Heinz Hofmann ◽

Gerd Weigelt ◽

Markus Wittkowski

Keyword(s):

Radiative Transfer ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Large Telescope ◽

Previous Estimate ◽

Long Baseline ◽

Very Large Telescope ◽

Radiative Transfer Modeling ◽

Stellar Source ◽

Dusty Torus

AbstractWe present mid-IR long-baseline interferometric observations of the red supergiant WOH G64 in the Large Magellanic Cloud with MIDI at the ESO's Very Large Telescope Interferometer (VLTI). Our MIDI observations of WOH G64 are the first VLTI observations to spatially resolve an individual stellar source in an extragalactic system. Our 2-D radiative transfer modeling reveals the presence of a geometrically and optically thick torus seen nearly pole-on. This model brings WOH G64 in much better agreement with the current evolutionary tracks for a 25 M⊙ star — about a half of the previous estimate of 40 M⊙ — and solves the serious discrepancy between theory and observation which existed for this object.

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Radiation-induced surface decomposition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075592 ◽

1983 ◽

Vol 41 ◽

pp. 368-369

Author(s):

M. L. Knotek

Keyword(s):

Ionizing Radiation ◽

Atomic Structure ◽

Chemical Bonding ◽

Neutral Species ◽

Radiation Induced ◽

Physical And Chemical ◽

Surface Decomposition ◽

The Relationship ◽

Electron And Photon ◽

Surface Bond

Modern surface analysis is based largely upon the use of ionizing radiation to probe the electronic and atomic structure of the surfaces physical and chemical makeup. In many of these studies the ionizing radiation used as the primary probe is found to induce changes in the structure and makeup of the surface, especially when electrons are employed. A number of techniques employ the phenomenon of radiation induced desorption as a means of probing the nature of the surface bond. These include Electron- and Photon-Stimulated Desorption (ESD and PSD) which measure desorbed ionic and neutral species as they leave the surface after the surface has been excited by some incident ionizing particle. There has recently been a great deal of activity in determining the relationship between the nature of chemical bonding and its susceptibility to radiation damage.

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