Polarisation by Thomson scattering in optically thin stellar envelopes. III. A statistical study of the oblateness and rotation of Be star envelopes.
Abstract
Summary. The two statistical problems of interpreting the intrinsic circumstellar polarisations R = p sin2 i and the apparent rotation speeds U = V sin i for a group of Be stars with randomly oriented axial inclinations (i) are discussed. Each can be reduced to Abel's integral equation for the true distribution of the actual polarisation parameter p (an effective oblateness . Brown and McLean, Paper I) and of the actual equatorial rotation speed V The difficulties of accurate inversion of this equation are briefly discussed and it is proposed that this is best done in terms of moment analysis of the distributions along the lines of Chandrasekhar and Miinch (1950). Such a moment analysis is carried out for a sample of 67 Be stars, for which R and U data are available, this being the largest list of its type. The results are discussed in terms of the physics of the objects and the V distribution compared to earlier conclusions. In particular the p distribution is found to be very skew toward small values where the polarisations are hardest to measure and to separate from the interstellar component. Key words: stellar envelopes - polarisation - stellar rotations - Be stars
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- October 1978
- Bibcode:
- 1978A&A....69..291M
- Keywords:
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- Be Stars:Rotation;
- Emission-Line Stars:Envelopes;
- Polarization:Stellar Envelopes;
- Scattering:Stellar Envelopes