---
_id: '11622'
abstract:
- lang: eng
  text: 'The recent discovery of low-amplitude dipolar oscillation mixed modes in
    massive red giants indicates the presence of a missing physical process inside
    their cores. Stars more massive than ∼ 1.3 M⊙ are known to develop a convective
    core during the main-sequence: the dynamo process triggered by this convection
    could be the origin of a strong magnetic field inside the core of the star, trapped
    when it becomes stably stratified and for the rest of its evolution. The presence
    of highly magnetized white dwarfs strengthens the hypothesis of buried fossil
    magnetic fields inside the core of evolved low-mass stars. If such a fossil field
    exists, it should affect the mixed modes of red giants as they are sensitive to
    processes affecting the deepest layers of these stars. The impact of a magnetic
    field on dipolar oscillations modes was one of Pr. Michael J. Thompson’s research
    topics during the 90s when preparing the helioseismic SoHO space mission. As the
    detection of gravity modes in the Sun is still controversial, the investigation
    of the solar oscillation modes did not provide any hint of the existence of a
    magnetic field in the solar radiative core. Today we have access to the core of
    evolved stars thanks to the asteroseismic observation of mixed modes from CoRoT,
    Kepler, K2 and TESS missions. The idea of applying and generalizing the work done
    for the Sun came from discussions with Pr. Michael Thompson in early 2018 before
    we lost him. Following the path we drew together, we theoretically investigate
    the effect of a stable axisymmetric mixed poloidal and toroidal magnetic field,
    aligned with the rotation axis of the star, on the mixed modes frequencies of
    a typical evolved low-mass star. This enables us to estimate the magnetic perturbations
    to the eigenfrequencies of mixed dipolar modes, depending on the magnetic field
    strength and the evolutionary state of the star. We conclude that strong magnetic
    fields of ∼ 1MG should perturb the mixed-mode frequency pattern enough for its
    effects to be detectable inside current asteroseismic data.'
acknowledgement: The authors of this work acknowledge the support received from the
  PLATO CNES grant, the National Aeronautics and Space Administration under Grant
  NNX15AF13G, by the National Science Foundation grant AST-1411685, the Ramon y Cajal
  fellowship number RYC-2015-17697, the ERC SPIRE grant (647383), and the Fundation
  L’Oréal-Unesco-Académie des sciences.
alternative_title:
- Astrophysics and Space Science Proceedings
article_processing_charge: No
arxiv: 1
author:
- first_name: Lisa Annabelle
  full_name: Bugnet, Lisa Annabelle
  id: d9edb345-f866-11ec-9b37-d119b5234501
  last_name: Bugnet
  orcid: 0000-0003-0142-4000
- first_name: V.
  full_name: Prat, V.
  last_name: Prat
- first_name: S.
  full_name: Mathis, S.
  last_name: Mathis
- first_name: R. A.
  full_name: García, R. A.
  last_name: García
- first_name: S.
  full_name: Mathur, S.
  last_name: Mathur
- first_name: K.
  full_name: Augustson, K.
  last_name: Augustson
- first_name: C.
  full_name: Neiner, C.
  last_name: Neiner
- first_name: M. J.
  full_name: Thompson, M. J.
  last_name: Thompson
citation:
  ama: 'Bugnet LA, Prat V, Mathis S, et al. The impact of a fossil magnetic field
    on dipolar mixed-mode frequencies in sub- and red-giant stars. In: Monteiro M,
    Garcia RA, Christensen-Dalsgaard J, McIntosh SW, eds. <i>Dynamics of the Sun and
    Stars</i>. Vol 57. 1st ed. ASSSP. Cham: Springer Nature; 2020:251-257. doi:<a
    href="https://doi.org/10.1007/978-3-030-55336-4_33">10.1007/978-3-030-55336-4_33</a>'
  apa: 'Bugnet, L. A., Prat, V., Mathis, S., García, R. A., Mathur, S., Augustson,
    K., … Thompson, M. J. (2020). The impact of a fossil magnetic field on dipolar
    mixed-mode frequencies in sub- and red-giant stars. In M. Monteiro, R. A. Garcia,
    J. Christensen-Dalsgaard, &#38; S. W. McIntosh (Eds.), <i>Dynamics of the Sun
    and Stars</i> (1st ed., Vol. 57, pp. 251–257). Cham: Springer Nature. <a href="https://doi.org/10.1007/978-3-030-55336-4_33">https://doi.org/10.1007/978-3-030-55336-4_33</a>'
  chicago: 'Bugnet, Lisa Annabelle, V. Prat, S. Mathis, R. A. García, S. Mathur, K.
    Augustson, C. Neiner, and M. J. Thompson. “The Impact of a Fossil Magnetic Field
    on Dipolar Mixed-Mode Frequencies in Sub- and Red-Giant Stars.” In <i>Dynamics
    of the Sun and Stars</i>, edited by Mario Monteiro, Rafael A Garcia, Jorgen Christensen-Dalsgaard,
    and Scott W McIntosh, 1st ed., 57:251–57. ASSSP. Cham: Springer Nature, 2020.
    <a href="https://doi.org/10.1007/978-3-030-55336-4_33">https://doi.org/10.1007/978-3-030-55336-4_33</a>.'
  ieee: 'L. A. Bugnet <i>et al.</i>, “The impact of a fossil magnetic field on dipolar
    mixed-mode frequencies in sub- and red-giant stars,” in <i>Dynamics of the Sun
    and Stars</i>, 1st ed., vol. 57, M. Monteiro, R. A. Garcia, J. Christensen-Dalsgaard,
    and S. W. McIntosh, Eds. Cham: Springer Nature, 2020, pp. 251–257.'
  ista: 'Bugnet LA, Prat V, Mathis S, García RA, Mathur S, Augustson K, Neiner C,
    Thompson MJ. 2020.The impact of a fossil magnetic field on dipolar mixed-mode
    frequencies in sub- and red-giant stars. In: Dynamics of the Sun and Stars. Astrophysics
    and Space Science Proceedings, vol. 57, 251–257.'
  mla: Bugnet, Lisa Annabelle, et al. “The Impact of a Fossil Magnetic Field on Dipolar
    Mixed-Mode Frequencies in Sub- and Red-Giant Stars.” <i>Dynamics of the Sun and
    Stars</i>, edited by Mario Monteiro et al., 1st ed., vol. 57, Springer Nature,
    2020, pp. 251–57, doi:<a href="https://doi.org/10.1007/978-3-030-55336-4_33">10.1007/978-3-030-55336-4_33</a>.
  short: L.A. Bugnet, V. Prat, S. Mathis, R.A. García, S. Mathur, K. Augustson, C.
    Neiner, M.J. Thompson, in:, M. Monteiro, R.A. Garcia, J. Christensen-Dalsgaard,
    S.W. McIntosh (Eds.), Dynamics of the Sun and Stars, 1st ed., Springer Nature,
    Cham, 2020, pp. 251–257.
date_created: 2022-07-19T08:25:41Z
date_published: 2020-12-19T00:00:00Z
date_updated: 2022-08-22T08:07:42Z
day: '19'
doi: 10.1007/978-3-030-55336-4_33
edition: '1'
editor:
- first_name: Mario
  full_name: Monteiro, Mario
  last_name: Monteiro
- first_name: Rafael A
  full_name: Garcia, Rafael A
  last_name: Garcia
- first_name: Jorgen
  full_name: Christensen-Dalsgaard, Jorgen
  last_name: Christensen-Dalsgaard
- first_name: Scott W
  full_name: McIntosh, Scott W
  last_name: McIntosh
extern: '1'
external_id:
  arxiv:
  - '2012.08684'
intvolume: '        57'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2012.08684
month: '12'
oa: 1
oa_version: Preprint
page: 251-257
place: Cham
publication: Dynamics of the Sun and Stars
publication_identifier:
  eisbn:
  - 978-3-030-55336-4
  eissn:
  - 1570-6605
  isbn:
  - 978-3-030-55335-7
  issn:
  - 1570-6591
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
scopus_import: '1'
series_title: ASSSP
status: public
title: The impact of a fossil magnetic field on dipolar mixed-mode frequencies in
  sub- and red-giant stars
type: book_chapter
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 57
year: '2020'
...