A dominant magnetic dipole for the evolved Ap star candidate EK Eridani
International audience Context. 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. Aims: We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of...
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
2011
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Online Access: | https://hal.science/hal-00647934 https://doi.org/10.1051/0004-6361/201117502 |
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ftutoulouse3hal:oai:HAL:hal-00647934v1 |
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Université Toulouse III - Paul Sabatier: HAL-UPS |
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ftutoulouse3hal |
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English |
topic |
stars: magnetic field stars: late-type stars: individual: EK Eridani [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] |
spellingShingle |
stars: magnetic field stars: late-type stars: individual: EK Eridani [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] Aurière, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J.-F. Charbonnel, Corinne Dintrans, B. Lignières, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. A dominant magnetic dipole for the evolved Ap star candidate EK Eridani |
topic_facet |
stars: magnetic field stars: late-type stars: individual: EK Eridani [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] |
description |
International audience Context. 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. Aims: We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. Methods: 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. We studied the classical activity indicators, the Ca ii H and K lines, the Ca ii infrared triplet, and Hα line, as well as the stellar radial velocity. Results: 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. Conclusions: 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 ... |
author2 |
Institut de recherche en astrophysique et planétologie (IRAP) 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) Софийски университет = Sofia University Laboratoire Astrophysique de Toulouse-Tarbes (LATT) Université de Genève = University of Geneva (UNIGE) Cranfield University |
format |
Article in Journal/Newspaper |
author |
Aurière, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J.-F. Charbonnel, Corinne Dintrans, B. Lignières, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. |
author_facet |
Aurière, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J.-F. Charbonnel, Corinne Dintrans, B. Lignières, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. |
author_sort |
Aurière, 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 |
HAL CCSD |
publishDate |
2011 |
url |
https://hal.science/hal-00647934 https://doi.org/10.1051/0004-6361/201117502 |
genre |
narval narval |
genre_facet |
narval narval |
op_source |
ISSN: 0004-6361 EISSN: 1432-0756 Astronomy and Astrophysics - A&A https://hal.science/hal-00647934 Astronomy and Astrophysics - A&A, 2011, 534, pp.139. ⟨10.1051/0004-6361/201117502⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/arxiv/1109.5570 info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201117502 hal-00647934 https://hal.science/hal-00647934 ARXIV: 1109.5570 BIBCODE: 2011A&A.534A.139A doi:10.1051/0004-6361/201117502 |
op_doi |
https://doi.org/10.1051/0004-6361/201117502 |
container_title |
Astronomy & Astrophysics |
container_volume |
534 |
container_start_page |
A139 |
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1810486268602089472 |
spelling |
ftutoulouse3hal:oai:HAL:hal-00647934v1 2024-09-15T18:41:53+00:00 A dominant magnetic dipole for the evolved Ap star candidate EK Eridani Aurière, M. Konstantinova-Antova, R. Petit, P. Roudier, T. Donati, J.-F. Charbonnel, Corinne Dintrans, B. Lignières, F. Wade, G. A. Morgenthaler, A. Tsvetkova, S. Institut de recherche en astrophysique et planétologie (IRAP) 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) Софийски университет = Sofia University Laboratoire Astrophysique de Toulouse-Tarbes (LATT) Université de Genève = University of Geneva (UNIGE) Cranfield University 2011-10 https://hal.science/hal-00647934 https://doi.org/10.1051/0004-6361/201117502 en eng HAL CCSD EDP Sciences info:eu-repo/semantics/altIdentifier/arxiv/1109.5570 info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201117502 hal-00647934 https://hal.science/hal-00647934 ARXIV: 1109.5570 BIBCODE: 2011A&A.534A.139A doi:10.1051/0004-6361/201117502 ISSN: 0004-6361 EISSN: 1432-0756 Astronomy and Astrophysics - A&A https://hal.science/hal-00647934 Astronomy and Astrophysics - A&A, 2011, 534, pp.139. ⟨10.1051/0004-6361/201117502⟩ stars: magnetic field stars: late-type stars: individual: EK Eridani [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] info:eu-repo/semantics/article Journal articles 2011 ftutoulouse3hal https://doi.org/10.1051/0004-6361/201117502 2024-06-24T23:59:17Z International audience Context. 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. Aims: We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. Methods: 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. We studied the classical activity indicators, the Ca ii H and K lines, the Ca ii infrared triplet, and Hα line, as well as the stellar radial velocity. Results: 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. Conclusions: 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 ... Article in Journal/Newspaper narval narval Université Toulouse III - Paul Sabatier: HAL-UPS Astronomy & Astrophysics 534 A139 |