Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum
Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. We have previously discovered linear polarization signatures associated with individual lines in the spectra of cool and evolved stars. Here, we investigate whether a...
Main Authors: | , , , , , , , , , , , , , , , , , |
---|---|
Format: | Text |
Language: | unknown |
Published: |
arXiv
2016
|
Subjects: | |
Online Access: | https://dx.doi.org/10.48550/arxiv.1605.04702 https://arxiv.org/abs/1605.04702 |
id |
ftdatacite:10.48550/arxiv.1605.04702 |
---|---|
record_format |
openpolar |
spelling |
ftdatacite:10.48550/arxiv.1605.04702 2023-05-15T18:50:44+02:00 Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum Aurière, M. Ariste, A. López Mathias, P. Lèbre, A. Josselin, E. Montargès, M. Petit, P. Chiavassa, A. Paletou, F. Fabas, N. Konstantinova-Antova, R. Donati, J. -F. Grunhut, J. H. Wade, G. A. Herpin, F. Kervella, P. Perrin, G. Tessore, B. 2016 https://dx.doi.org/10.48550/arxiv.1605.04702 https://arxiv.org/abs/1605.04702 unknown arXiv https://dx.doi.org/10.1051/0004-6361/201628077 arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences article-journal Article ScholarlyArticle Text 2016 ftdatacite https://doi.org/10.48550/arxiv.1605.04702 https://doi.org/10.1051/0004-6361/201628077 2022-04-01T11:34:15Z Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. We have previously discovered linear polarization signatures associated with individual lines in the spectra of cool and evolved stars. Here, we investigate whether a similar linearly polarized spectrum exists for Betelgeuse. We used the spectropolarimeter Narval, combining multiple polarimetric sequences to obtain high signal-to-noise ratio spectra of individual lines, as well as the least-squares deconvolution (LSD) approach. We have discovered the existence of a linearly polarized spectrum for Betelgeuse, detecting a rather strong signal (at a few times 10$^{-4}$ of the continuum intensity level), both in individual lines and in the LSD profiles. Studying its properties and the signal observed for the resonant \ion{Na}{i}\,D lines, we conclude that we are mainly observing depolarization of the continuum by the absorption lines. The linear polarization of the Betelgeuse continuum is due to the anisotropy of the radiation field induced by brightness spots at the surface and Rayleigh scattering in the atmosphere. We have developed a geometrical model to interpret the observed polarization, from which we infer the presence of two brightness spots and their positions on the surface of Betelgeuse. We show that applying the model to each velocity bin along the Stokes Q and U profiles allows the derivation of a map of the bright spots. We use the Narval linear polarization observations of Betelgeuse obtained over a period of 1.4 years to study the evolution of the spots. Our study of the linearly polarized spectrum of Betelgeuse provides a novel method for studying the evolution of brightness spots at its surface and complements quasi-simultaneous observations obtained with PIONIER at the VLTI. : 13 pages, 10 figures, accepted for publication in Astronomy and Astrophysics Text narval narval DataCite Metadata Store (German National Library of Science and Technology) |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
unknown |
topic |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences |
spellingShingle |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences Aurière, M. Ariste, A. López Mathias, P. Lèbre, A. Josselin, E. Montargès, M. Petit, P. Chiavassa, A. Paletou, F. Fabas, N. Konstantinova-Antova, R. Donati, J. -F. Grunhut, J. H. Wade, G. A. Herpin, F. Kervella, P. Perrin, G. Tessore, B. Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
topic_facet |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences |
description |
Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. We have previously discovered linear polarization signatures associated with individual lines in the spectra of cool and evolved stars. Here, we investigate whether a similar linearly polarized spectrum exists for Betelgeuse. We used the spectropolarimeter Narval, combining multiple polarimetric sequences to obtain high signal-to-noise ratio spectra of individual lines, as well as the least-squares deconvolution (LSD) approach. We have discovered the existence of a linearly polarized spectrum for Betelgeuse, detecting a rather strong signal (at a few times 10$^{-4}$ of the continuum intensity level), both in individual lines and in the LSD profiles. Studying its properties and the signal observed for the resonant \ion{Na}{i}\,D lines, we conclude that we are mainly observing depolarization of the continuum by the absorption lines. The linear polarization of the Betelgeuse continuum is due to the anisotropy of the radiation field induced by brightness spots at the surface and Rayleigh scattering in the atmosphere. We have developed a geometrical model to interpret the observed polarization, from which we infer the presence of two brightness spots and their positions on the surface of Betelgeuse. We show that applying the model to each velocity bin along the Stokes Q and U profiles allows the derivation of a map of the bright spots. We use the Narval linear polarization observations of Betelgeuse obtained over a period of 1.4 years to study the evolution of the spots. Our study of the linearly polarized spectrum of Betelgeuse provides a novel method for studying the evolution of brightness spots at its surface and complements quasi-simultaneous observations obtained with PIONIER at the VLTI. : 13 pages, 10 figures, accepted for publication in Astronomy and Astrophysics |
format |
Text |
author |
Aurière, M. Ariste, A. López Mathias, P. Lèbre, A. Josselin, E. Montargès, M. Petit, P. Chiavassa, A. Paletou, F. Fabas, N. Konstantinova-Antova, R. Donati, J. -F. Grunhut, J. H. Wade, G. A. Herpin, F. Kervella, P. Perrin, G. Tessore, B. |
author_facet |
Aurière, M. Ariste, A. López Mathias, P. Lèbre, A. Josselin, E. Montargès, M. Petit, P. Chiavassa, A. Paletou, F. Fabas, N. Konstantinova-Antova, R. Donati, J. -F. Grunhut, J. H. Wade, G. A. Herpin, F. Kervella, P. Perrin, G. Tessore, B. |
author_sort |
Aurière, M. |
title |
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
title_short |
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
title_full |
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
title_fullStr |
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
title_full_unstemmed |
Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum |
title_sort |
discovery of a complex linearly polarized spectrum of betelgeuse dominated by depolarization of the continuum |
publisher |
arXiv |
publishDate |
2016 |
url |
https://dx.doi.org/10.48550/arxiv.1605.04702 https://arxiv.org/abs/1605.04702 |
genre |
narval narval |
genre_facet |
narval narval |
op_relation |
https://dx.doi.org/10.1051/0004-6361/201628077 |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.1605.04702 https://doi.org/10.1051/0004-6361/201628077 |
_version_ |
1766244496432955392 |