The intrinsic and interstellar broad-band linear polarization of nearby FGK dwarfs
Article
Article Title | The intrinsic and interstellar broad-band linear polarization of nearby FGK dwarfs |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Cotton, Daniel V. (Author), Marshall, Jonathan P. (Author), Bailey, Jeremy (Author), Kedziora-Chudczer, Lucyna (Author), Bott, Kimberly (Author), Marsden, Stephen C. (Author) and Carter, Bradley D. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 467 (1), pp. 873-897 |
Number of Pages | 25 |
Year | 2017 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stx068 |
Web Address (URL) | https://academic.oup.com/mnras/article/467/1/873/2896680 |
Abstract | We present linear polarization measurements of nearby FGK dwarfs to parts-per-million (ppm) precision. Before making any allowance for interstellar polarization, we found that the active stars within the sample have a mean polarization of 28.5 ± 2.2 ppm, while the inactive stars have amean of 9.6±1.5 ppm. Amongst inactive stars, we initially found no difference between debris disc host stars (9.1 ± 2.5 ppm) and the other FGK dwarfs (9.9 ± 1.9 ppm).We develop a model for the magnitude and direction of interstellar polarization for nearby stars. When we correct the observations for the estimated interstellar polarization, we obtain 23.0 ± 2.2 ppm for the active stars, 7.8 ± 2.9 ppm for the inactive debris disc host stars and 2.9 ± 1.9 ppm for the other inactive stars. The data indicate that whilst some debris disc host stars are intrinsically polarized most inactive FGK dwarfs have negligible intrinsic polarization, but that active dwarfs have intrinsic polarization at levels ranging up to ~45 ppm. We briefly consider a number of mechanisms, and suggest that differential saturation of spectral lines in the presence of magnetic fields is best able to explain the polarization seen in active dwarfs. The results have implications for current attempts to detect polarized reflected light from hot Jupiters by looking at the combined light of the star and planet. |
Keywords | Circumstellar matter; Dust; Extinction; ISM: magnetic fields; Stars: activity; Stars: solartype; Techniques: polarimetric |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of New South Wales |
Computational Engineering and Science Research Centre | |
Institution of Origin | University of Southern Queensland |
Funder | Australian Research Council |
https://research.usq.edu.au/item/q488v/the-intrinsic-and-interstellar-broad-band-linear-polarization-of-nearby-fgk-dwarfs
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