On the polarimetric variability of bright O-type stars

Clarke, D., McDavid, D., Smith, R.A. and Henrichs, H.F. (2002) On the polarimetric variability of bright O-type stars. Astronomy and Astrophysics, 383(2), pp. 580-590. (doi: 10.1051/0004-6361:20011787)

Abstract

Polarimetric data associated with multi-parameter observational campaigns of selected bright O-type stars and their variable winds, are analysed in relation to the outcomes of the UV and optical spectroscopic studies. For the stars ξ Per and λ Cep, individual measurement uncertainties are Δρ~±0.0002 with nightly mean uncertainties of Δρ~±0.00007. Although variability is apparent on a night-to-night basis, with differences in δρ~0.0002, no correlations are found between these and the periodic behaviours associated with the stellar Si IV and H α lines. Similar polarimetric variability is seen in the data for the standard star ø Cas used as a reference in this observing campaign. It is suggested that all of these low level fluctuations are not intrinsic to the stars but are engendered by structured instrumental polarization in the diffraction pattern and depolarization effects in combination with inconsistent target acquisition and with variable seeing conditions in the Earth's atmosphere. Reassessment of older data for λ Cep from Hayes (1978) also supports this thesis.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Clarke, Dr David
• Authors: Clarke, D., McDavid, D., Smith, R.A., and Henrichs, H.F.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Astronomy and Astrophysics
• Publisher: EDP Sciences
• ISSN: 0004-6361
• ISSN (Online): 1432-0746
• Copyright Holders: Copyright © 2002 EDP Sciences
• First Published: First published in Astronomy and Astrophysics 383(2):580-590
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher