Polarization due to rotational distortion in the bright star Regulus
Letter
Article Title | Polarization due to rotational distortion in the bright star Regulus |
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ERA Journal ID | 213748 |
Article Category | Letter |
Authors | Cotton, Daniel V., Bailey, Jeremy, Howarth, Ian D., Bott, Kimberly, Kedziora-Chudczer, Lucyna, Lucas, P. W. and Hough, J. H. |
Journal Title | Nature Astronomy |
Journal Citation | 1 (10), pp. 690-696 |
Number of Pages | 7 |
Year | 2017 |
Publisher | Nature Publishing Group |
Place of Publication | United Kingdom |
ISSN | 2397-3366 |
Digital Object Identifier (DOI) | https://doi.org/10.1038/s41550-017-0238-6 |
Web Address (URL) | https://www.nature.com/articles/s41550-017-0238-6 |
Abstract | Polarization in stars was first predicted by Chandrasekhar 1, who calculated a substantial linear polarization at the stellar limb for a pure electron-scattering atmosphere. This polarization will average to zero when integrated over a spherical star but could be detected if the symmetry was broken, for example, by the eclipse of a binary companion. Nearly 50 years ago, Harrington and Collins 2 modelled another way of breaking the symmetry and producing net polarization-the distortion of a rapidly rotating hot star. Here we report the first detection of this effect. Observations of the linear polarization of Regulus, with two different high-precision polarimeters, range from +42 ppm at a wavelength of 741 nm to-22 ppm at 395 nm. The reversal from red to blue is a distinctive feature of rotation-induced polarization. Using a new set of models for the polarization of rapidly rotating stars, we find that Regulus is rotating at 96.5-0.8+0.6% 96. 5-0.8 + 0.6 % of its critical angular velocity for break-up, and has an inclination greater than 76.5°. The rotation axis of the star is at a position angle of 79.5 ± 0.7°. The conclusions are independent of, but in good agreement with, the results of previously published interferometric observations of Regulus 3. The accurate measurement of rotation in early-type stars is important for understanding their stellar environments 4 and the course of their evolution 5. |
Keywords | wavelength dependence; linear-polarization; intrinsic polarization; echelle spectograph; model; polarimeter; radiation |
ANZSRC Field of Research 2020 | 5101. Astronomical sciences |
Public Notes | Files associated with this item cannot be displayed due to copyright restrictions. |
Funder | Australian Research Council |
Byline Affiliations | University of New South Wales |
University College London, United Kingdom | |
Virtual Planetary Laboratory, United States | |
University of Washington, United States | |
University of Hertfordshire, United Kingdom |
https://research.usq.edu.au/item/wz8wq/polarization-due-to-rotational-distortion-in-the-bright-star-regulus
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