Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis
International audience Context. An extremely weak circularly polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A. A weak surface magnetic field was proposed to account for the observed polarized signal, but the shape of the phase-averaged signatu...
Published in: | Astronomy & Astrophysics |
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Main Authors: | , , , , , , , , , , , |
Other Authors: | , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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HAL CCSD
2016
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Online Access: | https://hal.science/hal-02320325 https://doi.org/10.1051/0004-6361/201527556 |
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ftcollegfrance:oai:HAL:hal-02320325v1 |
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Open Polar |
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Collège de France: HAL |
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language |
English |
topic |
"stars: individual: θLeo" "stars: individual: βUMa" "stars: chemically peculiar" "Astrophysics - Solar and Stellar Astrophysics" "stars: magnetic field" [SDU]Sciences of the Universe [physics] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] |
spellingShingle |
"stars: individual: θLeo" "stars: individual: βUMa" "stars: chemically peculiar" "Astrophysics - Solar and Stellar Astrophysics" "stars: magnetic field" [SDU]Sciences of the Universe [physics] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] Blazère, A. Petit, P. Lignieres, F. Aurière, M. Ballot, J. Böhm, T. Folsom, C. Gaurat, M. Jouve, L. Lopez Ariste, A. Neiner, C. Wade, G., A Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
topic_facet |
"stars: individual: θLeo" "stars: individual: βUMa" "stars: chemically peculiar" "Astrophysics - Solar and Stellar Astrophysics" "stars: magnetic field" [SDU]Sciences of the Universe [physics] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] |
description |
International audience Context. An extremely weak circularly polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A. A weak surface magnetic field was proposed to account for the observed polarized signal, but the shape of the phase-averaged signature, dominated by a prominent positive lobe, is not expected in the standard theory of the Zeeman effect.Aims: We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, β UMa and θ Leo, and investigating the physical origin of Sirius-like polarized signals further.Methods: We present here a set of deep spectropolarimetric observations of β UMa and θ Leo, observed with the NARVAL spectropolarimeter. We analyzed all spectra with the least squares deconvolution multiline procedure. To improve the signal-to-noise ratio and detect extremely weak signatures in Stokes V profiles, we co-added all available spectra of each star (around 150 observations each time). Finally, we ran several tests to evaluate whether the detected signatures are consistent with the behavior expected from the Zeeman effect.Results: The line profiles of the two stars display circularly polarized signatures similar in shape and amplitude to the observations previously gathered for Sirius A. Our series of tests brings further evidence of a magnetic origin of the recorded signal.Conclusions: These new detections suggest that very weak magnetic fields may well be present in the photospheres of a significant fraction of intermediate-mass stars. The strongly asymmetric Zeeman signatures measured so far in Am stars (featuring a dominant single-sign lobe) are not expected in the standard theory of the Zeeman effect and may be linked to sharp vertical gradients in photospheric velocities and magnetic field strengths. |
author2 |
Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA) Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS) Laboratoire Astrophysique de Toulouse-Tarbes (LATT) Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) Institut de recherche en astrophysique et planétologie (IRAP) Institut de Biologie du Développement de Marseille (IBDM) Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Centre National de la Recherche Scientifique (CNRS) Télescope héliographique pour l'étude du magnétisme et des instabilites solaires (THEMIS) Centre National de la Recherche Scientifique (CNRS) Royal Military College of Canada |
format |
Article in Journal/Newspaper |
author |
Blazère, A. Petit, P. Lignieres, F. Aurière, M. Ballot, J. Böhm, T. Folsom, C. Gaurat, M. Jouve, L. Lopez Ariste, A. Neiner, C. Wade, G., A |
author_facet |
Blazère, A. Petit, P. Lignieres, F. Aurière, M. Ballot, J. Böhm, T. Folsom, C. Gaurat, M. Jouve, L. Lopez Ariste, A. Neiner, C. Wade, G., A |
author_sort |
Blazère, A. |
title |
Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
title_short |
Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
title_full |
Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
title_fullStr |
Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
title_full_unstemmed |
Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis |
title_sort |
detection of ultra-weak magnetic fields in am stars: β ursae majoris and θ leonis |
publisher |
HAL CCSD |
publishDate |
2016 |
url |
https://hal.science/hal-02320325 https://doi.org/10.1051/0004-6361/201527556 |
genre |
narval narval |
genre_facet |
narval narval |
op_source |
ISSN: 0004-6361 EISSN: 1432-0756 Astronomy and Astrophysics - A&A https://hal.science/hal-02320325 Astronomy and Astrophysics - A&A, 2016, 586, pp.A97. ⟨10.1051/0004-6361/201527556⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/arxiv/1601.01829 info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201527556 hal-02320325 https://hal.science/hal-02320325 ARXIV: 1601.01829 BIBCODE: 2016A&A.586A.97B doi:10.1051/0004-6361/201527556 |
op_doi |
https://doi.org/10.1051/0004-6361/201527556 |
container_title |
Astronomy & Astrophysics |
container_volume |
586 |
container_start_page |
A97 |
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1799468745659252736 |
spelling |
ftcollegfrance:oai:HAL:hal-02320325v1 2024-05-19T07:50:09+00:00 Detection of ultra-weak magnetic fields in Am stars: β Ursae Majoris and θ Leonis Blazère, A. Petit, P. Lignieres, F. Aurière, M. Ballot, J. Böhm, T. Folsom, C. Gaurat, M. Jouve, L. Lopez Ariste, A. Neiner, C. Wade, G., A Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA) Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS) Laboratoire Astrophysique de Toulouse-Tarbes (LATT) Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) Institut de recherche en astrophysique et planétologie (IRAP) Institut de Biologie du Développement de Marseille (IBDM) Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Centre National de la Recherche Scientifique (CNRS) Télescope héliographique pour l'étude du magnétisme et des instabilites solaires (THEMIS) Centre National de la Recherche Scientifique (CNRS) Royal Military College of Canada 2016-02 https://hal.science/hal-02320325 https://doi.org/10.1051/0004-6361/201527556 en eng HAL CCSD EDP Sciences info:eu-repo/semantics/altIdentifier/arxiv/1601.01829 info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201527556 hal-02320325 https://hal.science/hal-02320325 ARXIV: 1601.01829 BIBCODE: 2016A&A.586A.97B doi:10.1051/0004-6361/201527556 ISSN: 0004-6361 EISSN: 1432-0756 Astronomy and Astrophysics - A&A https://hal.science/hal-02320325 Astronomy and Astrophysics - A&A, 2016, 586, pp.A97. ⟨10.1051/0004-6361/201527556⟩ "stars: individual: θLeo" "stars: individual: βUMa" "stars: chemically peculiar" "Astrophysics - Solar and Stellar Astrophysics" "stars: magnetic field" [SDU]Sciences of the Universe [physics] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] info:eu-repo/semantics/article Journal articles 2016 ftcollegfrance https://doi.org/10.1051/0004-6361/201527556 2024-04-22T02:19:24Z International audience Context. An extremely weak circularly polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A. A weak surface magnetic field was proposed to account for the observed polarized signal, but the shape of the phase-averaged signature, dominated by a prominent positive lobe, is not expected in the standard theory of the Zeeman effect.Aims: We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, β UMa and θ Leo, and investigating the physical origin of Sirius-like polarized signals further.Methods: We present here a set of deep spectropolarimetric observations of β UMa and θ Leo, observed with the NARVAL spectropolarimeter. We analyzed all spectra with the least squares deconvolution multiline procedure. To improve the signal-to-noise ratio and detect extremely weak signatures in Stokes V profiles, we co-added all available spectra of each star (around 150 observations each time). Finally, we ran several tests to evaluate whether the detected signatures are consistent with the behavior expected from the Zeeman effect.Results: The line profiles of the two stars display circularly polarized signatures similar in shape and amplitude to the observations previously gathered for Sirius A. Our series of tests brings further evidence of a magnetic origin of the recorded signal.Conclusions: These new detections suggest that very weak magnetic fields may well be present in the photospheres of a significant fraction of intermediate-mass stars. The strongly asymmetric Zeeman signatures measured so far in Am stars (featuring a dominant single-sign lobe) are not expected in the standard theory of the Zeeman effect and may be linked to sharp vertical gradients in photospheric velocities and magnetic field strengths. Article in Journal/Newspaper narval narval Collège de France: HAL Astronomy & Astrophysics 586 A97 |