Magnetic geometry and surface differential rotation of the bright Am star Alhena A
International audience ABSTRACT Alhena A (γ Gem A) is a bright Am star, with the strongest disc-integrated magnetic field strength reported so far for an Am star. Its spectrum exhibits standard circularly polarized Zeeman signatures, contrary to all previously studied Am stars that display abnormal...
Published in: | Monthly Notices of the Royal Astronomical Society |
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ftunivnantes:oai:HAL:hal-03230745v1 2023-05-15T18:50:48+02:00 Magnetic geometry and surface differential rotation of the bright Am star Alhena A Blazère, Aurore Petit, Pascal Neiner, Coralie Folsom, Colin Kochukhov, Oleg Mathis, Stéphane Deal, Morgan Landstreet, John Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) 2020-03-11 https://hal.archives-ouvertes.fr/hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745/document https://hal.archives-ouvertes.fr/hal-03230745/file/stz3637.pdf https://doi.org/10.1093/mnras/stz3637 en eng HAL CCSD Oxford University Press (OUP): Policy P - Oxford Open Option A info:eu-repo/semantics/altIdentifier/arxiv/1912.08688 info:eu-repo/semantics/altIdentifier/doi/10.1093/mnras/stz3637 hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745/document https://hal.archives-ouvertes.fr/hal-03230745/file/stz3637.pdf ARXIV: 1912.08688 BIBCODE: 2020MNRAS.492.5794B doi:10.1093/mnras/stz3637 info:eu-repo/semantics/OpenAccess ISSN: 0035-8711 EISSN: 1365-2966 Monthly Notices of the Royal Astronomical Society https://hal.archives-ouvertes.fr/hal-03230745 Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2020, 492 (4), pp.5794-5810. ⟨10.1093/mnras/stz3637⟩ [PHYS]Physics [physics] [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] info:eu-repo/semantics/article Journal articles 2020 ftunivnantes https://doi.org/10.1093/mnras/stz3637 2022-08-09T23:51:50Z International audience ABSTRACT Alhena A (γ Gem A) is a bright Am star, with the strongest disc-integrated magnetic field strength reported so far for an Am star. Its spectrum exhibits standard circularly polarized Zeeman signatures, contrary to all previously studied Am stars that display abnormal signatures dominated by a single-signed lobe. We present here the result of follow-up observations of Alhena, using very high signal-to-noise spectropolarimetric data obtained over 25 observing nights with NARVAL at Télescope Bernard Lyot, in the frame of the BRITE (BRIght Target Explorer) spectropolarimetric survey. We confirm that Alhena A is magnetic and we determine its surface magnetic properties using different methods. Inclined dipole models are used to reproduce the longitudinal field measurements, as well as the Stokes V line profiles themselves. In both cases, the model is consistent with a polar field strength of ∼30 G. This is confirmed by a Zeeman-Doppler Imaging (ZDI) model, which also unveils smaller scale magnetic structures. A rotational period of 8.975 d was identified using intensity line profile variations. The ZDI inversion suggests that the surface magnetic field is sheared by differential rotation, with a difference in rotation rate between high and low latitudes at about 15 per cent of the solar value. This result challenges theories of the development of surface differential rotation in intermediate mass main-sequence stars. Article in Journal/Newspaper narval narval Université de Nantes: HAL-UNIV-NANTES Monthly Notices of the Royal Astronomical Society 492 4 5794 5810 |
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Université de Nantes: HAL-UNIV-NANTES |
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ftunivnantes |
language |
English |
topic |
[PHYS]Physics [physics] [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] |
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[PHYS]Physics [physics] [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] Blazère, Aurore Petit, Pascal Neiner, Coralie Folsom, Colin Kochukhov, Oleg Mathis, Stéphane Deal, Morgan Landstreet, John Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
topic_facet |
[PHYS]Physics [physics] [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] |
description |
International audience ABSTRACT Alhena A (γ Gem A) is a bright Am star, with the strongest disc-integrated magnetic field strength reported so far for an Am star. Its spectrum exhibits standard circularly polarized Zeeman signatures, contrary to all previously studied Am stars that display abnormal signatures dominated by a single-signed lobe. We present here the result of follow-up observations of Alhena, using very high signal-to-noise spectropolarimetric data obtained over 25 observing nights with NARVAL at Télescope Bernard Lyot, in the frame of the BRITE (BRIght Target Explorer) spectropolarimetric survey. We confirm that Alhena A is magnetic and we determine its surface magnetic properties using different methods. Inclined dipole models are used to reproduce the longitudinal field measurements, as well as the Stokes V line profiles themselves. In both cases, the model is consistent with a polar field strength of ∼30 G. This is confirmed by a Zeeman-Doppler Imaging (ZDI) model, which also unveils smaller scale magnetic structures. A rotational period of 8.975 d was identified using intensity line profile variations. The ZDI inversion suggests that the surface magnetic field is sheared by differential rotation, with a difference in rotation rate between high and low latitudes at about 15 per cent of the solar value. This result challenges theories of the development of surface differential rotation in intermediate mass main-sequence stars. |
author2 |
Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité) |
format |
Article in Journal/Newspaper |
author |
Blazère, Aurore Petit, Pascal Neiner, Coralie Folsom, Colin Kochukhov, Oleg Mathis, Stéphane Deal, Morgan Landstreet, John |
author_facet |
Blazère, Aurore Petit, Pascal Neiner, Coralie Folsom, Colin Kochukhov, Oleg Mathis, Stéphane Deal, Morgan Landstreet, John |
author_sort |
Blazère, Aurore |
title |
Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
title_short |
Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
title_full |
Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
title_fullStr |
Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
title_full_unstemmed |
Magnetic geometry and surface differential rotation of the bright Am star Alhena A |
title_sort |
magnetic geometry and surface differential rotation of the bright am star alhena a |
publisher |
HAL CCSD |
publishDate |
2020 |
url |
https://hal.archives-ouvertes.fr/hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745/document https://hal.archives-ouvertes.fr/hal-03230745/file/stz3637.pdf https://doi.org/10.1093/mnras/stz3637 |
genre |
narval narval |
genre_facet |
narval narval |
op_source |
ISSN: 0035-8711 EISSN: 1365-2966 Monthly Notices of the Royal Astronomical Society https://hal.archives-ouvertes.fr/hal-03230745 Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2020, 492 (4), pp.5794-5810. ⟨10.1093/mnras/stz3637⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/arxiv/1912.08688 info:eu-repo/semantics/altIdentifier/doi/10.1093/mnras/stz3637 hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745 https://hal.archives-ouvertes.fr/hal-03230745/document https://hal.archives-ouvertes.fr/hal-03230745/file/stz3637.pdf ARXIV: 1912.08688 BIBCODE: 2020MNRAS.492.5794B doi:10.1093/mnras/stz3637 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1093/mnras/stz3637 |
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Monthly Notices of the Royal Astronomical Society |
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492 |
container_issue |
4 |
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5794 |
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5810 |
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1766244550728220672 |