Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo
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 pos...
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ftdatacite:10.48550/arxiv.1601.01829 2023-05-15T18:50:48+02:00 Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo Blazère, A. Petit, P. Lignières, F. Aurière, M. ballot, J. Böhm, T. Folsom, C. P. Gaurat, M. Jouve, L. Ariste, A. Lopez Neiner, C. Wade, G. A. 2016 https://dx.doi.org/10.48550/arxiv.1601.01829 https://arxiv.org/abs/1601.01829 unknown arXiv https://dx.doi.org/10.1051/0004-6361/201527556 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.1601.01829 https://doi.org/10.1051/0004-6361/201527556 2022-04-01T11:34:54Z 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. We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, beta UMa and theta Leo, and investigating the physical origin of Sirius-like polarized signals further. We present here a set of deep spectropolarimetric observations of beta UMa and theta 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. 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. 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. Text narval narval DataCite Metadata Store (German National Library of Science and Technology) Sirius ENVELOPE(163.250,163.250,-84.133,-84.133) |
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DataCite Metadata Store (German National Library of Science and Technology) |
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ftdatacite |
language |
unknown |
topic |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences |
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Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences Blazère, A. Petit, P. Lignières, F. Aurière, M. ballot, J. Böhm, T. Folsom, C. P. Gaurat, M. Jouve, L. Ariste, A. Lopez Neiner, C. Wade, G. A. Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
topic_facet |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences |
description |
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. We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, beta UMa and theta Leo, and investigating the physical origin of Sirius-like polarized signals further. We present here a set of deep spectropolarimetric observations of beta UMa and theta 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. 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. 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. |
format |
Text |
author |
Blazère, A. Petit, P. Lignières, F. Aurière, M. ballot, J. Böhm, T. Folsom, C. P. Gaurat, M. Jouve, L. Ariste, A. Lopez Neiner, C. Wade, G. A. |
author_facet |
Blazère, A. Petit, P. Lignières, F. Aurière, M. ballot, J. Böhm, T. Folsom, C. P. Gaurat, M. Jouve, L. Ariste, A. Lopez Neiner, C. Wade, G. A. |
author_sort |
Blazère, A. |
title |
Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
title_short |
Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
title_full |
Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
title_fullStr |
Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
title_full_unstemmed |
Detection of ultra-weak magnetic fields in Am stars: beta UMa and theta Leo |
title_sort |
detection of ultra-weak magnetic fields in am stars: beta uma and theta leo |
publisher |
arXiv |
publishDate |
2016 |
url |
https://dx.doi.org/10.48550/arxiv.1601.01829 https://arxiv.org/abs/1601.01829 |
long_lat |
ENVELOPE(163.250,163.250,-84.133,-84.133) |
geographic |
Sirius |
geographic_facet |
Sirius |
genre |
narval narval |
genre_facet |
narval narval |
op_relation |
https://dx.doi.org/10.1051/0004-6361/201527556 |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.1601.01829 https://doi.org/10.1051/0004-6361/201527556 |
_version_ |
1766244561609293824 |