---
_id: '11621'
abstract:
- lang: eng
  text: "Context. Asteroseismology has revealed small core-to-surface rotation contrasts
    in stars in the whole Hertzsprung–Russell diagram. This is the signature of strong
    transport of angular momentum (AM) in stellar interiors. One of the plausible
    candidates to efficiently carry AM is magnetic fields with various topologies
    that could be present in stellar radiative zones. Among them, strong axisymmetric
    azimuthal (toroidal) magnetic fields have received a lot of interest. Indeed,
    if they are subject to the so-called Tayler instability, the accompanying triggered
    Maxwell stresses can transport AM efficiently. In addition, the electromotive
    force induced by the fluctuations of magnetic and velocity fields could potentially
    sustain a dynamo action that leads to the regeneration of the initial strong axisymmetric
    azimuthal magnetic field.\r\n\r\nAims. The key question we aim to answer is whether
    we can detect signatures of these deep strong azimuthal magnetic fields. The only
    way to answer this question is asteroseismology, and the best laboratories of
    study are intermediate-mass and massive stars with external radiative envelopes.
    Most of these are rapid rotators during their main sequence. Therefore, we have
    to study stellar pulsations propagating in stably stratified, rotating, and potentially
    strongly magnetised radiative zones, namely magneto-gravito-inertial (MGI) waves.\r\n\r\nMethods.
    We generalise the traditional approximation of rotation (TAR) by simultaneously
    taking general axisymmetric differential rotation and azimuthal magnetic fields
    into account. Both the Coriolis acceleration and the Lorentz force are therefore
    treated in a non-perturbative way. Using this new formalism, we derive the asymptotic
    properties of MGI waves and their period spacings.\r\n\r\nResults. We find that
    toroidal magnetic fields induce a shift in the period spacings of gravity (g)
    and Rossby (r) modes. An equatorial azimuthal magnetic field with an amplitude
    of the order of 105 G leads to signatures that are detectable in period spacings
    for high-radial-order g and r modes in γ Doradus (γ Dor) and slowly pulsating
    B (SPB) stars. More complex hemispheric configurations are more difficult to observe,
    particularly when they are localised out of the propagation region of MGI modes,
    which can be localised in an equatorial belt.\r\n\r\nConclusions. The magnetic
    TAR, which takes into account toroidal magnetic fields in a non-perturbative way,
    is derived. This new formalism allows us to assess the effects of the magnetic
    field in γ Dor and SPB stars on g and r modes. We find that these effects should
    be detectable for equatorial fields thanks to modern space photometry using observations
    from Kepler, TESS CVZ, and PLATO."
acknowledgement: 'We thank the referee for her/his positive and constructive report,
  which has allowed us to improve the quality of our article. H.D. and S.M. acknowledge
  support from the CNES PLATO grant at CEA/DAp. T.V.R. gratefully acknowledges support
  from the Research Foundation Flanders (FWO) under grant agreement No. 12ZB620N and
  V414021N. This research was supported in part by the National Science Foundation
  under Grant No. NSF PHY-1748958. C.A. is supported by the KU Leuven Research Council
  (grant C16/18/005: PARADISE) as well as from the BELgian federal Science Policy
  Office (BELSPO) through a PLATO PRODEX grant.'
article_number: A133
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: H.
  full_name: Dhouib, H.
  last_name: Dhouib
- first_name: S.
  full_name: Mathis, S.
  last_name: Mathis
- 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: T.
  full_name: Van Reeth, T.
  last_name: Van Reeth
- first_name: C.
  full_name: Aerts, C.
  last_name: Aerts
citation:
  ama: 'Dhouib H, Mathis S, Bugnet LA, Van Reeth T, Aerts C. Detecting deep axisymmetric
    toroidal magnetic fields in stars: The traditional approximation of rotation for
    differentially rotating deep spherical shells with a general azimuthal magnetic
    field. <i>Astronomy &#38; Astrophysics</i>. 2022;661. doi:<a href="https://doi.org/10.1051/0004-6361/202142956">10.1051/0004-6361/202142956</a>'
  apa: 'Dhouib, H., Mathis, S., Bugnet, L. A., Van Reeth, T., &#38; Aerts, C. (2022).
    Detecting deep axisymmetric toroidal magnetic fields in stars: The traditional
    approximation of rotation for differentially rotating deep spherical shells with
    a general azimuthal magnetic field. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences.
    <a href="https://doi.org/10.1051/0004-6361/202142956">https://doi.org/10.1051/0004-6361/202142956</a>'
  chicago: 'Dhouib, H., S. Mathis, Lisa Annabelle Bugnet, T. Van Reeth, and C. Aerts.
    “Detecting Deep Axisymmetric Toroidal Magnetic Fields in Stars: The Traditional
    Approximation of Rotation for Differentially Rotating Deep Spherical Shells with
    a General Azimuthal Magnetic Field.” <i>Astronomy &#38; Astrophysics</i>. EDP
    Sciences, 2022. <a href="https://doi.org/10.1051/0004-6361/202142956">https://doi.org/10.1051/0004-6361/202142956</a>.'
  ieee: 'H. Dhouib, S. Mathis, L. A. Bugnet, T. Van Reeth, and C. Aerts, “Detecting
    deep axisymmetric toroidal magnetic fields in stars: The traditional approximation
    of rotation for differentially rotating deep spherical shells with a general azimuthal
    magnetic field,” <i>Astronomy &#38; Astrophysics</i>, vol. 661. EDP Sciences,
    2022.'
  ista: 'Dhouib H, Mathis S, Bugnet LA, Van Reeth T, Aerts C. 2022. Detecting deep
    axisymmetric toroidal magnetic fields in stars: The traditional approximation
    of rotation for differentially rotating deep spherical shells with a general azimuthal
    magnetic field. Astronomy &#38; Astrophysics. 661, A133.'
  mla: 'Dhouib, H., et al. “Detecting Deep Axisymmetric Toroidal Magnetic Fields in
    Stars: The Traditional Approximation of Rotation for Differentially Rotating Deep
    Spherical Shells with a General Azimuthal Magnetic Field.” <i>Astronomy &#38;
    Astrophysics</i>, vol. 661, A133, EDP Sciences, 2022, doi:<a href="https://doi.org/10.1051/0004-6361/202142956">10.1051/0004-6361/202142956</a>.'
  short: H. Dhouib, S. Mathis, L.A. Bugnet, T. Van Reeth, C. Aerts, Astronomy &#38;
    Astrophysics 661 (2022).
date_created: 2022-07-19T08:04:15Z
date_published: 2022-05-19T00:00:00Z
date_updated: 2022-08-22T07:58:54Z
day: '19'
doi: 10.1051/0004-6361/202142956
extern: '1'
external_id:
  arxiv:
  - '2202.10026'
intvolume: '       661'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- magnetohydrodynamics (MHD) / waves / stars
- 'rotation / stars: magnetic field / stars'
- oscillations / methods
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2202.10026
month: '05'
oa: 1
oa_version: Preprint
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Detecting deep axisymmetric toroidal magnetic fields in stars: The traditional
  approximation of rotation for differentially rotating deep spherical shells with
  a general azimuthal magnetic field'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 661
year: '2022'
...
---
_id: '11605'
abstract:
- lang: eng
  text: "Context. The discovery of moderate differential rotation between the core
    and the envelope of evolved solar-like stars could be the signature of a strong
    magnetic field trapped inside the radiative interior. The population of intermediate-mass
    red giants presenting surprisingly low-amplitude mixed modes (i.e. oscillation
    modes that behave as acoustic modes in their external envelope and as gravity
    modes in their core) could also arise from the effect of an internal magnetic
    field. Indeed, stars more massive than about 1.1 solar masses are known to develop
    a convective core during their main sequence. The field generated by the dynamo
    triggered by this convection could be the progenitor of a strong fossil magnetic
    field trapped inside the core of the star for the remainder of its evolution.\r\n\r\nAims.
    Observations of mixed modes can constitute an excellent probe of the deepest layers
    of evolved solar-like stars, and magnetic fields in those regions can impact their
    propagation. The magnetic perturbation on mixed modes may therefore be visible
    in asteroseismic data. To unravel which constraints can be obtained from observations,
    we theoretically investigate the effects of a plausible mixed axisymmetric magnetic
    field with various amplitudes on the mixed-mode frequencies of evolved solar-like
    stars.\r\n\r\nMethods. First-order frequency perturbations due to an axisymmetric
    magnetic field were computed for dipolar and quadrupolar mixed modes. These computations
    were carried out for a range of stellar ages, masses, and metallicities.\r\n\r\nConclusions.
    We show that typical fossil-field strengths of 0.1 − 1 MG, consistent with the
    presence of a dynamo in the convective core during the main sequence, provoke
    significant asymmetries on mixed-mode frequency multiplets during the red giant
    branch. We provide constraints and methods for the detectability of such magnetic
    signatures. We show that these signatures may be detectable in asteroseismic data
    for field amplitudes small enough for the amplitude of the modes not to be affected
    by the conversion of gravity into Alfvén waves inside the magnetised interior.
    Finally, we infer an upper limit for the strength of the field and the associated
    lower limit for the timescale of its action in order to redistribute angular momentum
    in stellar interiors."
article_number: A53
article_processing_charge: No
article_type: original
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: A.
  full_name: Astoul, A.
  last_name: Astoul
- first_name: K.
  full_name: Augustson, K.
  last_name: Augustson
- first_name: R. A.
  full_name: García, R. A.
  last_name: García
- first_name: S.
  full_name: Mathur, S.
  last_name: Mathur
- first_name: L.
  full_name: Amard, L.
  last_name: Amard
- first_name: C.
  full_name: Neiner, C.
  last_name: Neiner
citation:
  ama: 'Bugnet LA, Prat V, Mathis S, et al. Magnetic signatures on mixed-mode frequencies:
    I. An axisymmetric fossil field inside the core of red giants. <i>Astronomy &#38;
    Astrophysics</i>. 2021;650. doi:<a href="https://doi.org/10.1051/0004-6361/202039159">10.1051/0004-6361/202039159</a>'
  apa: 'Bugnet, L. A., Prat, V., Mathis, S., Astoul, A., Augustson, K., García, R.
    A., … Neiner, C. (2021). Magnetic signatures on mixed-mode frequencies: I. An
    axisymmetric fossil field inside the core of red giants. <i>Astronomy &#38; Astrophysics</i>.
    EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202039159">https://doi.org/10.1051/0004-6361/202039159</a>'
  chicago: 'Bugnet, Lisa Annabelle, V. Prat, S. Mathis, A. Astoul, K. Augustson, R.
    A. García, S. Mathur, L. Amard, and C. Neiner. “Magnetic Signatures on Mixed-Mode
    Frequencies: I. An Axisymmetric Fossil Field inside the Core of Red Giants.” <i>Astronomy
    &#38; Astrophysics</i>. EDP Sciences, 2021. <a href="https://doi.org/10.1051/0004-6361/202039159">https://doi.org/10.1051/0004-6361/202039159</a>.'
  ieee: 'L. A. Bugnet <i>et al.</i>, “Magnetic signatures on mixed-mode frequencies:
    I. An axisymmetric fossil field inside the core of red giants,” <i>Astronomy &#38;
    Astrophysics</i>, vol. 650. EDP Sciences, 2021.'
  ista: 'Bugnet LA, Prat V, Mathis S, Astoul A, Augustson K, García RA, Mathur S,
    Amard L, Neiner C. 2021. Magnetic signatures on mixed-mode frequencies: I. An
    axisymmetric fossil field inside the core of red giants. Astronomy &#38; Astrophysics.
    650, A53.'
  mla: 'Bugnet, Lisa Annabelle, et al. “Magnetic Signatures on Mixed-Mode Frequencies:
    I. An Axisymmetric Fossil Field inside the Core of Red Giants.” <i>Astronomy &#38;
    Astrophysics</i>, vol. 650, A53, EDP Sciences, 2021, doi:<a href="https://doi.org/10.1051/0004-6361/202039159">10.1051/0004-6361/202039159</a>.'
  short: L.A. Bugnet, V. Prat, S. Mathis, A. Astoul, K. Augustson, R.A. García, S.
    Mathur, L. Amard, C. Neiner, Astronomy &#38; Astrophysics 650 (2021).
date_created: 2022-07-18T12:10:59Z
date_published: 2021-06-07T00:00:00Z
date_updated: 2022-08-19T10:06:33Z
day: '07'
doi: 10.1051/0004-6361/202039159
extern: '1'
external_id:
  arxiv:
  - '2102.01216'
intvolume: '       650'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- stars
- oscillations / stars
- magnetic field / stars
- interiors / stars
- evolution / stars
- rotation
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2102.01216
month: '06'
oa: 1
oa_version: Preprint
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Magnetic signatures on mixed-mode frequencies: I. An axisymmetric fossil field
  inside the core of red giants'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 650
year: '2021'
...
---
_id: '11608'
abstract:
- lang: eng
  text: 'In order to understand stellar evolution, it is crucial to efficiently determine
    stellar surface rotation periods. Indeed, while they are of great importance in
    stellar models, angular momentum transport processes inside stars are still poorly
    understood today. Surface rotation, which is linked to the age of the star, is
    one of the constraints needed to improve the way those processes are modelled.
    Statistics of the surface rotation periods for a large sample of stars of different
    spectral types are thus necessary. An efficient tool to automatically determine
    reliable rotation periods is needed when dealing with large samples of stellar
    photometric datasets. The objective of this work is to develop such a tool. For
    this purpose, machine learning classifiers constitute relevant bases to build
    our new methodology. Random forest learning abilities are exploited to automate
    the extraction of rotation periods in Kepler light curves. Rotation periods and
    complementary parameters are obtained via three different methods: a wavelet analysis,
    the autocorrelation function of the light curve, and the composite spectrum. We
    trained three different classifiers: one to detect if rotational modulations are
    present in the light curve, one to flag close binary or classical pulsators candidates
    that can bias our rotation period determination, and finally one classifier to
    provide the final rotation period. We tested our machine learning pipeline on
    23 431 stars of the Kepler K and M dwarf reference rotation catalogue for which
    60% of the stars have been visually inspected. For the sample of 21 707 stars
    where all the input parameters are provided to the algorithm, 94.2% of them are
    correctly classified (as rotating or not). Among the stars that have a rotation
    period in the reference catalogue, the machine learning provides a period that
    agrees within 10% of the reference value for 95.3% of the stars. Moreover, the
    yield of correct rotation periods is raised to 99.5% after visually inspecting
    25.2% of the stars. Over the two main analysis steps, rotation classification
    and period selection, the pipeline yields a global agreement with the reference
    values of 92.1% and 96.9% before and after visual inspection. Random forest classifiers
    are efficient tools to determine reliable rotation periods in large samples of
    stars. The methodology presented here could be easily adapted to extract surface
    rotation periods for stars with different spectral types or observed by other
    instruments such as K2, TESS or by PLATO in the near future.'
acknowledgement: 'We thank Suzanne Aigrain and Joe Llama for providing us with the
  simulated data used in Aigrain et al. (2015). S. N. B., L. B. and R. A. G. acknowledge
  the support from PLATO and GOLF CNES grants. A. R. G. S. acknowledges the support
  from NASA under grant NNX17AF27G. S. M. acknowledges the support from the Spanish
  Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697.
  P. L. P. and S. M. acknowledge support from the Spanish Ministry of Science and
  Innovation with the grant number PID2019-107187GB-I00. This research has made use
  of the NASA Exoplanet Archive, which is operated by the California Institute of
  Technology, under contract with the National Aeronautics and Space Administration
  under the Exoplanet Exploration Program. Software: Python (Van Rossum & Drake 2009),
  numpy (Oliphant 2006), pandas (The pandas development team 2020; McKinney 2010),
  matplotlib (Hunter 2007), scikit-learn (Pedregosa et al. 2011). The source code
  used to obtain the present results can be found at: https://gitlab.com/sybreton/pushkin
  ; https://gitlab.com/sybreton/ml_surface_rotation_paper .'
article_number: A125
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: S. N.
  full_name: Breton, S. N.
  last_name: Breton
- first_name: A. R. G.
  full_name: Santos, A. R. G.
  last_name: Santos
- 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: S.
  full_name: Mathur, S.
  last_name: Mathur
- first_name: R. A.
  full_name: García, R. A.
  last_name: García
- first_name: P. L.
  full_name: Pallé, P. L.
  last_name: Pallé
citation:
  ama: 'Breton SN, Santos ARG, Bugnet LA, Mathur S, García RA, Pallé PL. ROOSTER:
    A machine-learning analysis tool for Kepler stellar rotation periods. <i>Astronomy
    &#38; Astrophysics</i>. 2021;647. doi:<a href="https://doi.org/10.1051/0004-6361/202039947">10.1051/0004-6361/202039947</a>'
  apa: 'Breton, S. N., Santos, A. R. G., Bugnet, L. A., Mathur, S., García, R. A.,
    &#38; Pallé, P. L. (2021). ROOSTER: A machine-learning analysis tool for Kepler
    stellar rotation periods. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a
    href="https://doi.org/10.1051/0004-6361/202039947">https://doi.org/10.1051/0004-6361/202039947</a>'
  chicago: 'Breton, S. N., A. R. G. Santos, Lisa Annabelle Bugnet, S. Mathur, R. A.
    García, and P. L. Pallé. “ROOSTER: A Machine-Learning Analysis Tool for Kepler
    Stellar Rotation Periods.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences,
    2021. <a href="https://doi.org/10.1051/0004-6361/202039947">https://doi.org/10.1051/0004-6361/202039947</a>.'
  ieee: 'S. N. Breton, A. R. G. Santos, L. A. Bugnet, S. Mathur, R. A. García, and
    P. L. Pallé, “ROOSTER: A machine-learning analysis tool for Kepler stellar rotation
    periods,” <i>Astronomy &#38; Astrophysics</i>, vol. 647. EDP Sciences, 2021.'
  ista: 'Breton SN, Santos ARG, Bugnet LA, Mathur S, García RA, Pallé PL. 2021. ROOSTER:
    A machine-learning analysis tool for Kepler stellar rotation periods. Astronomy
    &#38; Astrophysics. 647, A125.'
  mla: 'Breton, S. N., et al. “ROOSTER: A Machine-Learning Analysis Tool for Kepler
    Stellar Rotation Periods.” <i>Astronomy &#38; Astrophysics</i>, vol. 647, A125,
    EDP Sciences, 2021, doi:<a href="https://doi.org/10.1051/0004-6361/202039947">10.1051/0004-6361/202039947</a>.'
  short: S.N. Breton, A.R.G. Santos, L.A. Bugnet, S. Mathur, R.A. García, P.L. Pallé,
    Astronomy &#38; Astrophysics 647 (2021).
date_created: 2022-07-18T12:21:32Z
date_published: 2021-03-19T00:00:00Z
date_updated: 2022-08-22T08:47:47Z
day: '19'
doi: 10.1051/0004-6361/202039947
extern: '1'
external_id:
  arxiv:
  - '2101.10152'
intvolume: '       647'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'methods: data analysis / stars: solar-type / stars: activity / stars: rotation
  / starspots'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2101.10152
month: '03'
oa: 1
oa_version: Preprint
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'ROOSTER: A machine-learning analysis tool for Kepler stellar rotation periods'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 647
year: '2021'
...
---
_id: '11609'
abstract:
- lang: eng
  text: "Context. Stellar interiors are the seat of efficient transport of angular
    momentum all along their evolution. In this context, understanding the dependence
    of the turbulent transport triggered by the instabilities of the vertical and
    horizontal shears of the differential rotation in stellar radiation zones as a
    function of their rotation, stratification, and thermal diffusivity is mandatory.
    Indeed, it constitutes one of the cornerstones of the rotational transport and
    mixing theory, which is implemented in stellar evolution codes to predict the
    rotational and chemical evolutions of stars.\r\n\r\nAims. We investigate horizontal
    shear instabilities in rotating stellar radiation zones by considering the full
    Coriolis acceleration with both the dimensionless horizontal Coriolis component
    f̃ and the vertical component f.\r\n\r\nMethods. We performed a linear stability
    analysis using linearized equations derived from the Navier-Stokes and heat transport
    equations in the rotating nontraditional f-plane. We considered a horizontal shear
    flow with a hyperbolic tangent profile as the base flow. The linear stability
    was analyzed numerically in wide ranges of parameters, and we performed an asymptotic
    analysis for large vertical wavenumbers using the Wentzel-Kramers-Brillouin-Jeffreys
    (WKBJ) approximation for nondiffusive and highly-diffusive fluids.\r\n\r\nResults.
    As in the traditional f-plane approximation, we identify two types of instabilities:
    the inflectional and inertial instabilities. The inflectional instability is destabilized
    as f̃ increases and its maximum growth rate increases significantly, while the
    thermal diffusivity stabilizes the inflectional instability similarly to the traditional
    case. The inertial instability is also strongly affected; for instance, the inertially
    unstable regime is also extended in the nondiffusive limit as 0 < f < 1 + f̃ 2/N2,
    where N is the dimensionless Brunt-Väisälä frequency. More strikingly, in the
    high thermal diffusivity limit, it is always inertially unstable at any colatitude
    θ except at the poles (i.e., 0° < θ <  180°). We also derived the critical Reynolds
    numbers for the inertial instability using the asymptotic dispersion relations
    obtained from the WKBJ analysis. Using the asymptotic and numerical results, we
    propose a prescription for the effective turbulent viscosities induced by the
    inertial and inflectional instabilities that can be possibly used in stellar evolution
    models. The characteristic time of this turbulence is short enough so that it
    is efficient to redistribute angular momentum and to mix chemicals in stellar
    radiation zones."
acknowledgement: The authors acknowledge support from the European Research Council
  through ERC grant SPIRE 647383 and from GOLF and PLATO CNES grants at the Department
  of Astrophysics at CEA Paris-Saclay. We thank the referee, Prof. A. J. Barker, for
  his constructive comments that allow us to improve the article.
article_number: A64
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: J.
  full_name: Park, J.
  last_name: Park
- first_name: V.
  full_name: Prat, V.
  last_name: Prat
- first_name: S.
  full_name: Mathis, S.
  last_name: Mathis
- first_name: Lisa Annabelle
  full_name: Bugnet, Lisa Annabelle
  id: d9edb345-f866-11ec-9b37-d119b5234501
  last_name: Bugnet
  orcid: 0000-0003-0142-4000
citation:
  ama: 'Park J, Prat V, Mathis S, Bugnet LA. Horizontal shear instabilities in rotating
    stellar radiation zones: II. Effects of the full Coriolis acceleration. <i>Astronomy
    &#38; Astrophysics</i>. 2021;646. doi:<a href="https://doi.org/10.1051/0004-6361/202038654">10.1051/0004-6361/202038654</a>'
  apa: 'Park, J., Prat, V., Mathis, S., &#38; Bugnet, L. A. (2021). Horizontal shear
    instabilities in rotating stellar radiation zones: II. Effects of the full Coriolis
    acceleration. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202038654">https://doi.org/10.1051/0004-6361/202038654</a>'
  chicago: 'Park, J., V. Prat, S. Mathis, and Lisa Annabelle Bugnet. “Horizontal Shear
    Instabilities in Rotating Stellar Radiation Zones: II. Effects of the Full Coriolis
    Acceleration.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2021. <a href="https://doi.org/10.1051/0004-6361/202038654">https://doi.org/10.1051/0004-6361/202038654</a>.'
  ieee: 'J. Park, V. Prat, S. Mathis, and L. A. Bugnet, “Horizontal shear instabilities
    in rotating stellar radiation zones: II. Effects of the full Coriolis acceleration,”
    <i>Astronomy &#38; Astrophysics</i>, vol. 646. EDP Sciences, 2021.'
  ista: 'Park J, Prat V, Mathis S, Bugnet LA. 2021. Horizontal shear instabilities
    in rotating stellar radiation zones: II. Effects of the full Coriolis acceleration.
    Astronomy &#38; Astrophysics. 646, A64.'
  mla: 'Park, J., et al. “Horizontal Shear Instabilities in Rotating Stellar Radiation
    Zones: II. Effects of the Full Coriolis Acceleration.” <i>Astronomy &#38; Astrophysics</i>,
    vol. 646, A64, EDP Sciences, 2021, doi:<a href="https://doi.org/10.1051/0004-6361/202038654">10.1051/0004-6361/202038654</a>.'
  short: J. Park, V. Prat, S. Mathis, L.A. Bugnet, Astronomy &#38; Astrophysics 646
    (2021).
date_created: 2022-07-18T13:24:32Z
date_published: 2021-02-08T00:00:00Z
date_updated: 2022-08-19T10:18:03Z
day: '08'
doi: 10.1051/0004-6361/202038654
extern: '1'
external_id:
  arxiv:
  - '2006.10660'
intvolume: '       646'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- hydrodynamics / turbulence / stars
- rotation / stars
- evolution
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/2006.10660
month: '02'
oa: 1
oa_version: Preprint
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Horizontal shear instabilities in rotating stellar radiation zones: II. Effects
  of the full Coriolis acceleration'
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 646
year: '2021'
...
---
_id: '11623'
abstract:
- lang: eng
  text: Brightness variations due to dark spots on the stellar surface encode information
    about stellar surface rotation and magnetic activity. In this work, we analyze
    the Kepler long-cadence data of 26,521 main-sequence stars of spectral types M
    and K in order to measure their surface rotation and photometric activity level.
    Rotation-period estimates are obtained by the combination of a wavelet analysis
    and autocorrelation function of the light curves. Reliable rotation estimates
    are determined by comparing the results from the different rotation diagnostics
    and four data sets. We also measure the photometric activity proxy Sph using the
    amplitude of the flux variations on an appropriate timescale. We report rotation
    periods and photometric activity proxies for about 60% of the sample, including
    4431 targets for which McQuillan et al. did not report a rotation period. For
    the common targets with rotation estimates in this study and in McQuillan et al.,
    our rotation periods agree within 99%. In this work, we also identify potential
    polluters, such as misclassified red giants and classical pulsator candidates.
    Within the parameter range we study, there is a mild tendency for hotter stars
    to have shorter rotation periods. The photometric activity proxy spans a wider
    range of values with increasing effective temperature. The rotation period and
    photometric activity proxy are also related, with Sph being larger for fast rotators.
    Similar to McQuillan et al., we find a bimodal distribution of rotation periods.
acknowledgement: "The authors thank Róbert Szabó Paul G. Beck, Katrien Kolenberg,
  and Isabel L. Colman for helping on the classification of stars. This paper includes
  data collected by the Kepler mission and obtained from the MAST data archive at
  the Space Telescope Science Institute (STScI). Funding for the Kepler mission is
  provided by the National Aeronautics and Space Administration (NASA) Science Mission
  Directorate. STScI is operated by the Association of Universities for Research in
  Astronomy, Inc., under NASA contract NAS 5–26555. A.R.G.S. acknowledges the support
  from NASA under grant NNX17AF27G. R.A.G. and L.B. acknowledge the support from PLATO
  and GOLF CNES grants. S.M. acknowledges the support from the Ramon y Cajal fellowship
  number RYC-2015-17697. T.S.M. acknowledges support from a Visiting Fellowship at
  the Max Planck Institute for Solar System Research. This research has made use of
  the NASA Exoplanet Archive, which is operated by the California Institute of Technology,
  under contract with the National Aeronautics and Space Administration under the
  Exoplanet Exploration Program.\r\n\r\nSoftware: KADACS (García et al. 2011), NumPy
  (van der Walt et al. 2011), SciPy (Jones et al. 2001), Matplotlib (Hunter 2007).\r\n\r\nFacilities:
  MAST - , Kepler Eclipsing Binary Catalog - , Exoplanet Archive. -"
article_number: '21'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: A. R. G.
  full_name: Santos, A. R. G.
  last_name: Santos
- first_name: R. A.
  full_name: García, R. A.
  last_name: García
- first_name: S.
  full_name: Mathur, S.
  last_name: Mathur
- 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: J. L.
  full_name: van Saders, J. L.
  last_name: van Saders
- first_name: T. S.
  full_name: Metcalfe, T. S.
  last_name: Metcalfe
- first_name: G. V. A.
  full_name: Simonian, G. V. A.
  last_name: Simonian
- first_name: M. H.
  full_name: Pinsonneault, M. H.
  last_name: Pinsonneault
citation:
  ama: Santos ARG, García RA, Mathur S, et al. Surface rotation and photometric activity
    for Kepler targets. I. M and K main-sequence stars. <i>The Astrophysical Journal
    Supplement Series</i>. 2019;244(1). doi:<a href="https://doi.org/10.3847/1538-4365/ab3b56">10.3847/1538-4365/ab3b56</a>
  apa: Santos, A. R. G., García, R. A., Mathur, S., Bugnet, L. A., van Saders, J.
    L., Metcalfe, T. S., … Pinsonneault, M. H. (2019). Surface rotation and photometric
    activity for Kepler targets. I. M and K main-sequence stars. <i>The Astrophysical
    Journal Supplement Series</i>. IOP Publishing. <a href="https://doi.org/10.3847/1538-4365/ab3b56">https://doi.org/10.3847/1538-4365/ab3b56</a>
  chicago: Santos, A. R. G., R. A. García, S. Mathur, Lisa Annabelle Bugnet, J. L.
    van Saders, T. S. Metcalfe, G. V. A. Simonian, and M. H. Pinsonneault. “Surface
    Rotation and Photometric Activity for Kepler Targets. I. M and K Main-Sequence
    Stars.” <i>The Astrophysical Journal Supplement Series</i>. IOP Publishing, 2019.
    <a href="https://doi.org/10.3847/1538-4365/ab3b56">https://doi.org/10.3847/1538-4365/ab3b56</a>.
  ieee: A. R. G. Santos <i>et al.</i>, “Surface rotation and photometric activity
    for Kepler targets. I. M and K main-sequence stars,” <i>The Astrophysical Journal
    Supplement Series</i>, vol. 244, no. 1. IOP Publishing, 2019.
  ista: Santos ARG, García RA, Mathur S, Bugnet LA, van Saders JL, Metcalfe TS, Simonian
    GVA, Pinsonneault MH. 2019. Surface rotation and photometric activity for Kepler
    targets. I. M and K main-sequence stars. The Astrophysical Journal Supplement
    Series. 244(1), 21.
  mla: Santos, A. R. G., et al. “Surface Rotation and Photometric Activity for Kepler
    Targets. I. M and K Main-Sequence Stars.” <i>The Astrophysical Journal Supplement
    Series</i>, vol. 244, no. 1, 21, IOP Publishing, 2019, doi:<a href="https://doi.org/10.3847/1538-4365/ab3b56">10.3847/1538-4365/ab3b56</a>.
  short: A.R.G. Santos, R.A. García, S. Mathur, L.A. Bugnet, J.L. van Saders, T.S.
    Metcalfe, G.V.A. Simonian, M.H. Pinsonneault, The Astrophysical Journal Supplement
    Series 244 (2019).
date_created: 2022-07-19T09:21:58Z
date_published: 2019-09-19T00:00:00Z
date_updated: 2022-08-22T08:10:38Z
day: '19'
doi: 10.3847/1538-4365/ab3b56
extern: '1'
external_id:
  arxiv:
  - '1908.05222'
intvolume: '       244'
issue: '1'
keyword:
- Space and Planetary Science
- Astronomy and Astrophysics
- 'methods: data analysis'
- 'stars: activity'
- 'stars: low-mass'
- 'stars: rotation'
- starspots
- 'techniques: photometric'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1908.05222
month: '09'
oa: 1
oa_version: Preprint
publication: The Astrophysical Journal Supplement Series
publication_identifier:
  issn:
  - 0067-0049
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: Surface rotation and photometric activity for Kepler targets. I. M and K main-sequence
  stars
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 244
year: '2019'
...
---
_id: '11627'
abstract:
- lang: eng
  text: 'For a solar-like star, the surface rotation evolves with time, allowing in
    principle to estimate the age of a star from its surface rotation period. Here
    we are interested in measuring surface rotation periods of solar-like stars observed
    by the NASA mission Kepler. Different methods have been developed to track rotation
    signals in Kepler photometric light curves: time-frequency analysis based on wavelet
    techniques, autocorrelation and composite spectrum. We use the learning abilities
    of random forest classifiers to take decisions during two crucial steps of the
    analysis. First, given some input parameters, we discriminate the considered Kepler
    targets between rotating MS stars, non-rotating MS stars, red giants, binaries
    and pulsators. We then use a second classifier only on the MS rotating targets
    to decide the best data analysis treatment.'
article_number: '1906.09609'
article_processing_charge: No
arxiv: 1
author:
- first_name: S. N.
  full_name: Breton, S. N.
  last_name: Breton
- 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: A. R. G.
  full_name: Santos, A. R. G.
  last_name: Santos
- first_name: A. Le
  full_name: Saux, A. Le
  last_name: Saux
- first_name: S.
  full_name: Mathur, S.
  last_name: Mathur
- first_name: P. L.
  full_name: Palle, P. L.
  last_name: Palle
- first_name: R. A.
  full_name: Garcia, R. A.
  last_name: Garcia
citation:
  ama: Breton SN, Bugnet LA, Santos ARG, et al. Determining surface rotation periods
    of solar-like stars observed by the Kepler mission using machine learning techniques.
    <i>arXiv</i>. doi:<a href="https://doi.org/10.48550/arXiv.1906.09609">10.48550/arXiv.1906.09609</a>
  apa: Breton, S. N., Bugnet, L. A., Santos, A. R. G., Saux, A. L., Mathur, S., Palle,
    P. L., &#38; Garcia, R. A. (n.d.). Determining surface rotation periods of solar-like
    stars observed by the Kepler mission using machine learning techniques. <i>arXiv</i>.
    <a href="https://doi.org/10.48550/arXiv.1906.09609">https://doi.org/10.48550/arXiv.1906.09609</a>
  chicago: Breton, S. N., Lisa Annabelle Bugnet, A. R. G. Santos, A. Le Saux, S. Mathur,
    P. L. Palle, and R. A. Garcia. “Determining Surface Rotation Periods of Solar-like
    Stars Observed by the Kepler Mission Using Machine Learning Techniques.” <i>ArXiv</i>,
    n.d. <a href="https://doi.org/10.48550/arXiv.1906.09609">https://doi.org/10.48550/arXiv.1906.09609</a>.
  ieee: S. N. Breton <i>et al.</i>, “Determining surface rotation periods of solar-like
    stars observed by the Kepler mission using machine learning techniques,” <i>arXiv</i>.
    .
  ista: Breton SN, Bugnet LA, Santos ARG, Saux AL, Mathur S, Palle PL, Garcia RA.
    Determining surface rotation periods of solar-like stars observed by the Kepler
    mission using machine learning techniques. arXiv, 1906.09609.
  mla: Breton, S. N., et al. “Determining Surface Rotation Periods of Solar-like Stars
    Observed by the Kepler Mission Using Machine Learning Techniques.” <i>ArXiv</i>,
    1906.09609, doi:<a href="https://doi.org/10.48550/arXiv.1906.09609">10.48550/arXiv.1906.09609</a>.
  short: S.N. Breton, L.A. Bugnet, A.R.G. Santos, A.L. Saux, S. Mathur, P.L. Palle,
    R.A. Garcia, ArXiv (n.d.).
date_created: 2022-07-20T11:18:53Z
date_published: 2019-06-23T00:00:00Z
date_updated: 2022-08-22T08:16:53Z
day: '23'
doi: 10.48550/arXiv.1906.09609
extern: '1'
external_id:
  arxiv:
  - '1906.09609'
keyword:
- asteroseismology
- rotation
- solar-like stars
- kepler
- machine learning
- random forest
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1906.09609
month: '06'
oa: 1
oa_version: Preprint
publication: arXiv
publication_status: submitted
status: public
title: Determining surface rotation periods of solar-like stars observed by the Kepler
  mission using machine learning techniques
type: preprint
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2019'
...