WACCABI—A 2D Radiative Transfer Code for Stellar Winds in Cataclysmic Binaries

Abstract Hot massive stars exhibit strong stellar winds that enrich the surrounding interstellar medium and affect the stars’ evolution. However, the winds are inhomogeneous (clumped) and are difficult to model in radiative transfer codes. To produce more realistic spectra many codes use a volume-filling factor approach to incorporate the effects of clumping. While this approach is convenient it is simplistic. We introduce an alternative approach to incorporate clumping by assuming the wind is composed of dense spherical shells. Using this approach in the radiative transfer code cmfgen we produce synthetic spectra for AzV83, an O7Iaf+ supergiant located in the Small Magellanic Cloud. The spectrum of AzV83 is rich in both photospheric and wind features, making it an ideal candidate with which to investigate the physical characteristics of stellar winds. Synthetic spectra are compared to the star’s observed spectrum to better characterize the influence of clumped winds on spectral features, and to better understand the limitations of the volume-filling factor approach. The approach using spherical shells yields similar wind parameters to those obtained using the volume-filling factor approach although a slightly higher mass-loss rate is required to fit Hα. As expected, the interclump medium in the model with shells allows the high ionisation resonance transitions of N v and O vi to be fitted using LX-ray/LBol ≈ 10−7 which is typically observed for O stars, and which is a factor of ten lower than needed with the volume-filling factor approach.

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Observational Effects of Corotating Interaction Regions in OB stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900195178 ◽

2004 ◽

Vol 215 ◽

pp. 47-48

Author(s):

R. Blomme

Keyword(s):

Radiative Transfer ◽

Radiative Transfer Model ◽

Transfer Model ◽

Stellar Winds ◽

Corotating Interaction Regions ◽

Ob Stars ◽

Interaction Regions

The stellar winds of OB stars are perturbed by Corotating Interaction Regions (CIRs). We present a 3D radiative transfer model which predicts that variations should occur in the infrared and millimetre continuum.

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Molecular Data Needs for Modelling AGB Stellar Winds and Other Molecular Environments

Galaxies ◽

10.3390/galaxies6030086 ◽

2018 ◽

Vol 6 (3) ◽

pp. 86

Author(s):

Taïssa Danilovich ◽

Leen Decin ◽

Marie Van de Sande

Keyword(s):

Radiative Transfer ◽

Excited States ◽

Molecular Data ◽

Stellar Winds ◽

Agb Stars ◽

Vibrationally Excited ◽

Highly Sensitive ◽

Transfer Modelling ◽

First Time ◽

Modern Era

The modern era of highly sensitive telescopes is enabling the detection of more and more molecular species in various astronomical environments. Many of these are now being carefully examined for the first time. However, to move beyond detection to more detailed analysis such as radiative transfer modelling, certain molecular properties need to be properly measured and calculated. The importance of contributions from vibrationally excited states or collisional (de-)excitations can vary greatly, depending on the specific molecule and the environment being studied. Here, we discuss the present molecular data needs for detailed radiative transfer modelling of observations of molecular rotational transitions, primarily in the (sub-)millimetre and adjacent regimes, and with a focus on the stellar winds of AGB stars.

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