A dominant magnetic dipole for the evolved Ap star candidate EK Eridani
EK Eri is one of the most slowly rotating active giants known, and has been proposed to be the descendant of a strongly magnetic Ap star. We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. We used the NARVA...
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ftdatacite:10.48550/arxiv.1109.5570 2023-05-15T18:50:50+02:00 A dominant magnetic dipole for the evolved Ap star candidate EK Eridani Auriere, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J. -F. Charbonnel, C. Dintrans, B. Lignieres, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. 2011 https://dx.doi.org/10.48550/arxiv.1109.5570 https://arxiv.org/abs/1109.5570 unknown arXiv https://dx.doi.org/10.1051/0004-6361/201117502 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 2011 ftdatacite https://doi.org/10.48550/arxiv.1109.5570 https://doi.org/10.1051/0004-6361/201117502 2022-04-01T14:00:42Z EK Eri is one of the most slowly rotating active giants known, and has been proposed to be the descendant of a strongly magnetic Ap star. We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. We used the NARVAL spectropolarimeter at the Bernard Lyot telescope at the Pic du Midi Observatory, along with the least-squares deconvolution method, to extract high signal-to-noise ratio Stokes V profiles from a timeseries of 28 polarisation spectra. We have derived the surface-averaged longitudinal magnetic field Bl. We fit the Stokes V profiles with a model of the large-scale magnetic field and obtained Zeeman Doppler images of the surface magnetic strength and geometry. Bl variations of up to about 80 G are observed without any reversal of its sign, and which are in phase with photometric ephemeris. The activity indicators are shown to vary smoothly on a timescale compatible with the rotational period inferred from photometry (308.8 d.), however large deviations can occur from one rotation to another. The surface magnetic field variations of EK Eri appear to be dominated by a strong magnetic spot (of negative polarity) which is phased with the dark (cool) photometric spot. Our modeling shows that the large-scale magnetic field of EK Eri is strongly poloidal. For a rotational axis inclination of i = 60°, we obtain a model that is almost purely dipolar. In the dipolar model, the strong magnetic/photometric spot corresponds to the negative pole of the dipole, which could be the remnant of that of an Ap star progenitor of EK Eri. Our observations and modeling conceptually support this hypothesis, suggesting an explanation of the outstanding magnetic properties of EK Eri as the result of interaction between deep convection and the remnant of an Ap star magnetic dipole. : 8 pages, 6 figures, accepted for publication in Astronomy & Astrophysics Text narval narval DataCite Metadata Store (German National Library of Science and Technology) |
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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 Auriere, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J. -F. Charbonnel, C. Dintrans, B. Lignieres, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
topic_facet |
Solar and Stellar Astrophysics astro-ph.SR FOS Physical sciences |
description |
EK Eri is one of the most slowly rotating active giants known, and has been proposed to be the descendant of a strongly magnetic Ap star. We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. We used the NARVAL spectropolarimeter at the Bernard Lyot telescope at the Pic du Midi Observatory, along with the least-squares deconvolution method, to extract high signal-to-noise ratio Stokes V profiles from a timeseries of 28 polarisation spectra. We have derived the surface-averaged longitudinal magnetic field Bl. We fit the Stokes V profiles with a model of the large-scale magnetic field and obtained Zeeman Doppler images of the surface magnetic strength and geometry. Bl variations of up to about 80 G are observed without any reversal of its sign, and which are in phase with photometric ephemeris. The activity indicators are shown to vary smoothly on a timescale compatible with the rotational period inferred from photometry (308.8 d.), however large deviations can occur from one rotation to another. The surface magnetic field variations of EK Eri appear to be dominated by a strong magnetic spot (of negative polarity) which is phased with the dark (cool) photometric spot. Our modeling shows that the large-scale magnetic field of EK Eri is strongly poloidal. For a rotational axis inclination of i = 60°, we obtain a model that is almost purely dipolar. In the dipolar model, the strong magnetic/photometric spot corresponds to the negative pole of the dipole, which could be the remnant of that of an Ap star progenitor of EK Eri. Our observations and modeling conceptually support this hypothesis, suggesting an explanation of the outstanding magnetic properties of EK Eri as the result of interaction between deep convection and the remnant of an Ap star magnetic dipole. : 8 pages, 6 figures, accepted for publication in Astronomy & Astrophysics |
format |
Text |
author |
Auriere, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J. -F. Charbonnel, C. Dintrans, B. Lignieres, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. |
author_facet |
Auriere, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J. -F. Charbonnel, C. Dintrans, B. Lignieres, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. |
author_sort |
Auriere, M. |
title |
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
title_short |
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
title_full |
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
title_fullStr |
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
title_full_unstemmed |
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
title_sort |
dominant magnetic dipole for the evolved ap star candidate ek eridani |
publisher |
arXiv |
publishDate |
2011 |
url |
https://dx.doi.org/10.48550/arxiv.1109.5570 https://arxiv.org/abs/1109.5570 |
genre |
narval narval |
genre_facet |
narval narval |
op_relation |
https://dx.doi.org/10.1051/0004-6361/201117502 |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.1109.5570 https://doi.org/10.1051/0004-6361/201117502 |
_version_ |
1766244596104298496 |