---
OA_place: publisher
_id: '19853'
abstract:
- lang: eng
  text: "The internal dynamical properties of red giant stars have been explored extensively
    in recent\r\nyears as a result of the increase in high precision data availability
    from the space missions\r\nKepler and TESS (Transiting Exoplanet Survey Satellite),
    and in this exploration, it has been\r\ndiscovered that some of these stars are
    not behaving as expected. Red giants are stars that have\r\nevolved off of the
    main sequence after having completed fusing hydrogen into helium in their\r\ncore.
    Observational data shows that the cores are rotating significantly slower than
    models can\r\nrecreate consistently across evolutionary stages. This discrepancy
    has prompted investigation\r\ninto the efficiency of angular momentum transport
    mechanisms and mixing processes including\r\nmeridional circulation, shear instability,
    internal gravity waves, Tayler-Spruit dynamo, fossil\r\nmagnetic fields etc.,
    to explain this behavior.\r\nAnalyzing seismic oscillations in stars, via asteroseismology,
    is a powerful tool as it is the only\r\nway in which the deep stellar interior
    can be probed and subsequently characterized; this is\r\npossible as global oscillations
    modulating the stellar surface are effected by internal processes.\r\nFor red
    giants, p-modes (pressure modes; resonating through the entire star) and g-modes\r\n(gravity-modes;
    resonating in the radiative interior) couple to create mixed modes. These\r\nmixed
    modes give access to the otherwise hidden stellar interior as g-modes couple to
    p-modes,\r\ndelivering information from the interior to the surface.\r\nInternal
    magnetic signatures have been observationally confirmed in red giant stars via\r\nasteroseismology
    and characterized in two ways. One being that dipole mixed modes with\r\nℓ = 1
    will display a global asymmetric frequency shift of its azimuthal components;
    where\r\nthe m = 0 and m = ±1 components of the ℓ = 1 dipole mode will be shifted
    by two\r\ndifferent power laws, respectively. And the other being a reduced visibility
    of dipole mixed\r\nmode amplitudes in the power spectra, where stars presenting
    with this feature are denoted as\r\nsuppressed.\r\nSeveral studies of the suppressed
    dipole mixed mode amplitudes have been carried out, but thus\r\nfar, no dedicated
    studies of the asymmetric frequency shifts of suppressed red giants have been\r\nconducted;
    one reason being that the asymmetric frequency shifts cannot be characterized\r\nwhen
    the dipole mixed mode amplitudes are severely reduced in many of the suppressed
    stars.\r\nSincefullysuppressedstarsdonothavedetectablemixed-modestoevaluate, partiallysuppressed\r\nstars,
    that is, red giant stars presenting with suppressed dipole mixed modes in select
    parts of\r\ntheir power spectra rather than across the entire spectra, will be
    the subject of this study as\r\nthe respective mode amplitudes are still visible
    at high frequencies.\r\nAs such, this study will search for asymmetric frequency
    shifts on the dipole mixed\r\nmodes of partially suppressed red giant stars; the
    aim here is to investigate if both\r\nmode suppression and magnetic shifting of
    dipole mixed modes occur simultaneously.\r\nThisstudywillbeconductedbycreatingapipelinetoestimatepriorsofasteroseismicparameters,\r\nuse
    the priors to model the power spectra with the stellar modeling code sloscillations_ISTA,\r\nand
    perform a Bayesian fit of the parameters with the simulated data on the star KIC
    6975038,\r\na target with partially suppressed dipolar mode amplitudes identified
    in the literature, to fit its\r\nmagnetic parameters. I present a novel method
    to model the stellar power spectra of\r\npartially suppressed red giants by application
    of a sigmoid profile to the ℓ= 1 dipolar\r\nmode component of the spectra. With
    the results of this study I aim at constraining\r\nthe cause of this partial dipole
    mode amplitude suppression, allowing for more detailed\r\nstudies regarding their
    astrophysical nature. Furthermore, the long term hope for the method\r\nused in
    this study will be to expand the sample of partially suppressed red giants and
    fit their\r\nasteroseismic parameters accordingly."
acknowledgement: "I would like to give thanks to myself for my hard work on this document.
  This paper includes data collected by the Kepler mission and obtained from the MAST
  data\r\narchive at the Space Telescope Science Institute (STScI). Funding for the
  Kepler mission is\r\nprovided by the NASA Science Mission Directorate. STScI is
  operated by the Association of\r\nUniversities for Research in Astronomy, Inc.,
  under NASA contract NAS 5–26555.\r\n"
alternative_title:
- ISTA Master's Thesis
article_processing_charge: No
author:
- first_name: Kanah
  full_name: Smith, Kanah
  id: 7703505d-3211-11ee-a6a9-a2ab9d936c15
  last_name: Smith
citation:
  ama: Smith K. Exploring internal magnetism in partially suppressed red giant stars.
    2025. doi:<a href="https://doi.org/10.15479/AT-ISTA-19853">10.15479/AT-ISTA-19853</a>
  apa: Smith, K. (2025). <i>Exploring internal magnetism in partially suppressed red
    giant stars</i>. Institute of Science and Technology Austria. <a href="https://doi.org/10.15479/AT-ISTA-19853">https://doi.org/10.15479/AT-ISTA-19853</a>
  chicago: Smith, Kanah. “Exploring Internal Magnetism in Partially Suppressed Red
    Giant Stars.” Institute of Science and Technology Austria, 2025. <a href="https://doi.org/10.15479/AT-ISTA-19853">https://doi.org/10.15479/AT-ISTA-19853</a>.
  ieee: K. Smith, “Exploring internal magnetism in partially suppressed red giant
    stars,” Institute of Science and Technology Austria, 2025.
  ista: Smith K. 2025. Exploring internal magnetism in partially suppressed red giant
    stars. Institute of Science and Technology Austria.
  mla: Smith, Kanah. <i>Exploring Internal Magnetism in Partially Suppressed Red Giant
    Stars</i>. Institute of Science and Technology Austria, 2025, doi:<a href="https://doi.org/10.15479/AT-ISTA-19853">10.15479/AT-ISTA-19853</a>.
  short: K. Smith, Exploring Internal Magnetism in Partially Suppressed Red Giant
    Stars, Institute of Science and Technology Austria, 2025.
corr_author: '1'
date_created: 2025-06-20T13:27:08Z
date_published: 2025-10-08T00:00:00Z
date_updated: 2026-04-07T12:01:37Z
day: '08'
ddc:
- '520'
degree_awarded: MS
department:
- _id: GradSch
- _id: LiBu
doi: 10.15479/AT-ISTA-19853
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has_accepted_license: '1'
keyword:
- asteroseismology
- stellar physics
- red giant
- magnetism
- suppressed
language:
- iso: eng
month: '10'
oa: 1
oa_version: Published Version
page: '38'
publication_identifier:
  issn:
  - 2791-4585
publication_status: published
publisher: Institute of Science and Technology Austria
status: public
supervisor:
- first_name: Lisa Annabelle
  full_name: Bugnet, Lisa Annabelle
  id: d9edb345-f866-11ec-9b37-d119b5234501
  last_name: Bugnet
  orcid: 0000-0003-0142-4000
title: Exploring internal magnetism in partially suppressed red giant stars
type: dissertation
user_id: ba8df636-2132-11f1-aed0-ed93e2281fdd
year: '2025'
...