subject:(Stellar Magnetism)

1. Buysschaert, Bram. Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars.

Degree: Docteur es, Astronomie et Astrophysique, 2018, Paris Sciences et Lettres (ComUE); Katholieke universiteit te Leuven (1970-....)

URL: http://www.theses.fr/2018PSLEO004

► Environ 10% des étoiles de type spectral O, B ou A ont un champ magnétique fort, détectable, stable et à grande échelle à leur surface,… (more)

▼ Environ 10% des étoiles de type spectral O, B ou A ont un champ magnétique fort, détectable, stable et à grande échelle à leur surface, qui ressemble le plus souvent à un dipôle. Des modèles théoriques et des simulations numériques prédisent ces champs magnétiques vus en surface pénètrent aussi dans les zones radiatives et influencent la structure interne. Les modèles prédisent que ces champs magnétiques imposent une rotation uniforme dans les zones radiatives et peuvent supprimer la pénétration convective autour du cœur. Cela a des conséquences sur l’évolution de ces étoiles chaudes magnétiques. Pour ce faire, l’astérosismologie est la meilleure méthode car les paramètres des pulsations stellaires sont directement liés aux conditions physiques internes. Plusieurs types de pulsations stellaires sont connus et classés en fonction de leur force de rappel. Parmi eux, les plus à même de sonder les régions proches du cœur des étoiles, sur lequel se concentre notre intérêt dans cette thèse sont les modes de gravité, qui sont gouvernés par la force d’Archimède.Notre premier objectif était d’identifier des étoiles chaudes, pulsantes et magnétiques et de caractériser leurs propriétés magnétiques et sismiques. Des étoiles ont été sélectionnées grâce à des diagnostics observationnels indirects de la présence d’un champ magnétique qou nous confirmons grâce à de la spectropolarimétrie optique à haute résolution obtenue avec ESPaDOnS, Narval et ESPaDOnS. Pour deux étoiles magnétiques connues, HD43317 et o Lup, nous avons caractérisé la géométrie et l’intensité du champ magnétique aves des séries temporelles spectropolarimétriques. Pour toutes les étoiles de notre échantillon, nous avons également obtenu des séries temporelles photométriques très précises grâce aux télescopes spatiaux BRITE, CoRoT ou K2 pour étudier leur variabilité (périodique) cohérente. Seulement HD43317 a révélé des dizaines de fréquences de pulsations stellaires, pointant plutôt vers des modes de gravité.Nous nous sommes ensuite concentrés sur HD43317 dans pour déterminer observationellement la structure interne de cette étoile magnétique chaude. Nous avons fait usage de modélisation sismique: les fréquences des modes de pulsations observées dans les données CoRoT, couvrant 150j, ont été ajustées à celles des modes gravito-inertiels calculés avec le code de pulsations GYRE couplé aux modèles MESA. Nous avons pu associer les fréquences des modes de pulsations à des séries de modes (l,m) = (1,−1) et (2,−1) se chevauchant. La petite zone de pénétration convective dans la zone radiative telle que déduite du modèle MESA optimal s’avère cohérente avec les prédictions théoriques. Néanmoins, les intervalles de confiance sur certains paramètres physiques issus des modèles sont très larges et compatibles avec les valeurs de la littérature pour des étoiles chaudes et pulsantes mais non-magnétiques. Nous en concluons que la série temporelle de 150j de données CoRoT est trop courte pour déterminer d’une manière non-équivoque la structure interne des étoiles magnétiques… Advisors/Committee Members: Neiner, Coralie Laurence (thesis director), Aerts, Conny (thesis director).

Subjects/Keywords: Étoiles chaudes; Étoiles pulsantes; Étoiles magnetiques; Astérosismologie; Magnétisme stellaire; Hot stars; Pulsating stars; Magnetic stars; Asteroseismology; Stellar magnetism; 520

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APA (6^th Edition):

Buysschaert, B. (2018). Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars. (Doctoral Dissertation). Paris Sciences et Lettres (ComUE); Katholieke universiteit te Leuven (1970-....). Retrieved from http://www.theses.fr/2018PSLEO004

Chicago Manual of Style (16^th Edition):

Buysschaert, Bram. “Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars.” 2018. Doctoral Dissertation, Paris Sciences et Lettres (ComUE); Katholieke universiteit te Leuven (1970-....). Accessed March 06, 2021. http://www.theses.fr/2018PSLEO004.

MLA Handbook (7^th Edition):

Buysschaert, Bram. “Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars.” 2018. Web. 06 Mar 2021.

Vancouver:

Buysschaert B. Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars. [Internet] [Doctoral dissertation]. Paris Sciences et Lettres (ComUE); Katholieke universiteit te Leuven (1970-....); 2018. [cited 2021 Mar 06]. Available from: http://www.theses.fr/2018PSLEO004.

Council of Science Editors:

Buysschaert B. Sismologie des étoiles chaudes magnétiques : Seismology of magnetic massive stars. [Doctoral Dissertation]. Paris Sciences et Lettres (ComUE); Katholieke universiteit te Leuven (1970-....); 2018. Available from: http://www.theses.fr/2018PSLEO004

Queens University

2. Shultz, Matthew. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .

Degree: Physics, Engineering Physics and Astronomy, 2016, Queens University

URL: http://hdl.handle.net/1974/14691

► How do the magnetic fields of massive stars evolve over time? Are their gyrochronological ages consistent with ages inferred from evolutionary tracks? Why do most… (more)

▼ How do the magnetic fields of massive stars evolve over time? Are their gyrochronological ages consistent with ages inferred from evolutionary tracks? Why do most stars predicted to host Centrifugal Magnetospheres (CMs) display no Hα emission? Does plasma escape from CMs via centrifugal breakout events, or by a steady-state leakage mechanism? This thesis investigates these questions via a population study with a sample of 51 magnetic early B-type stars. The longitudinal magnetic field \bz~was measured from Least Squares Deconvolution profiles extracted from high-resolution spectropolarimetric data. New rotational periods P_rot were determined for 15 stars from \bz, leaving only 3 stars for which P_rot is unknown. Projected rotational velocities \vsini~were measured from multiple spectral lines. Effective temperatures and surface gravities were measured via ionization balances and line profile fitting of H Balmer lines. Fundamental physical parameters, \bz, \vsini, and P_rot were then used to determine radii, masses, ages, dipole oblique rotator model, stellar wind, magnetospheric, and spindown parameters using a Monte Carlo approach that self-consistently calculates all parameters while accounting for all available constraints on stellar properties. Dipole magnetic field strengths B_d follow a log-normal distribution similar to that of Ap stars, and decline over time in a fashion consistent with the expected conservation of fossil magnetic flux. P_rot increases with fractional main sequence age, mass, and B_d, as expected from magnetospheric braking. However, comparison of evolutionary track ages to maximum spindown ages t_S,max shows that initial rotation fractions may be far below critical for stars with M_*>10 M_\odot. Computing t_S,max with different mass-loss prescriptions indicates that the mass-loss rates of B-type stars are likely much lower than expected from extrapolation from O-type stars. Stars with Hα in emission and absorption occupy distinct regions in the updated rotation-magnetic confinement diagram: Hα-bright stars are found to be younger, more rapidly rotating, and more strongly magnetized than the general population. Emission strength is sensitive both to the volume of the CM and to the mass-loss rate, favouring leakage over centrifugal breakout.

Subjects/Keywords: Stellar Winds ; Binary Stars ; Magnetospheres ; Massive Stars ; Magnetic Braking ; Stellar Magnetism ; Spectropolarimetry

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Shultz, M. (2016). The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/14691

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Shultz, Matthew. “The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .” 2016. Thesis, Queens University. Accessed March 06, 2021. http://hdl.handle.net/1974/14691.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Shultz, Matthew. “The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .” 2016. Web. 06 Mar 2021.

Vancouver:

Shultz M. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . [Internet] [Thesis]. Queens University; 2016. [cited 2021 Mar 06]. Available from: http://hdl.handle.net/1974/14691.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Shultz M. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . [Thesis]. Queens University; 2016. Available from: http://hdl.handle.net/1974/14691

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Colorado

3. Augustson, Kyle C. Convection and Dynamo Action in Massive Stars.

Degree: PhD, Astrophysical & Planetary Sciences, 2013, University of Colorado

URL: https://scholar.colorado.edu/astr_gradetds/26

► Contact between numerical simulations and observations of stellar magnetism is sought, with an emphasis on those stars that are the most readily observed and… (more)

▼ Contact between numerical simulations and observations of stellar magnetism is sought, with an emphasis on those stars that are the most readily observed and those that may have magnetic activity cycles: the Sun, F-type, and B-type stars. Two approaches are taken in studying stellar dynamos and dynamics, utilizing three-dimensional MHD simulations run on massively parallel supercomputers with the full spherical geometry and employing a new compressible code in the spherical wedge geometry. A 3D MHD simulation of the solar dynamo that utilizes the Anelastic Spherical Harmonic (ASH) code is presented. This simulation self-consistently exhibits four prominent aspects of solar magnetism: activity cycles, polarity cycles, the equatorward field migration, and grand minima. The ASH framework and this simulation’s ability to capture many aspects of the solar dynamo represent a first step toward a more complete model of the Sun’s global-scale magnetic activity and its cycles. The dynamics and dynamos of F-type stars are studied through global-scale ASH simulations, with significant contact made between the observed differential rotation and magnetic cycle periods of these stars and those achieved in the simulations. Separately, ASH simulations of core convection in the massive B-type stars show that generation of superequipartition magnetic fields with peak strengths above 1 MG is possible within their cores, which has implications for the evolution of these stars as well as for the properties of their remnants. The internal waves excited by overshooting convection and rotation in these stars radiative exteriors are assessed for their asteroseismic signatures. The results of 3D compressive MHD simulations of the solar near-surface shear layer with the Compressible Spherical Segment (CSS) code are shown, with such layers arising in the coupled dynamics of ASH and CSS as well as in a more rapidly rotating, thin convective envelope of an F-type star. Advisors/Committee Members: Juri Toomre, Bradley W. Hindman, Mark S. Miesch, Mark P. Rast, Jeffrey B. Weiss.

Subjects/Keywords: Dynamo Theory; Fluid Dynamics; Stellar Convection; Stellar Magnetism; Astrophysics and Astronomy; Physical Processes; Stars, Interstellar Medium and the Galaxy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Augustson, K. C. (2013). Convection and Dynamo Action in Massive Stars. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/astr_gradetds/26

Chicago Manual of Style (16^th Edition):

Augustson, Kyle C. “Convection and Dynamo Action in Massive Stars.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 06, 2021. https://scholar.colorado.edu/astr_gradetds/26.

MLA Handbook (7^th Edition):

Augustson, Kyle C. “Convection and Dynamo Action in Massive Stars.” 2013. Web. 06 Mar 2021.

Vancouver:

Augustson KC. Convection and Dynamo Action in Massive Stars. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 06]. Available from: https://scholar.colorado.edu/astr_gradetds/26.

Council of Science Editors:

Augustson KC. Convection and Dynamo Action in Massive Stars. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/astr_gradetds/26

Universidade do Rio Grande do Norte

4. Duarte, Tharcisyo Sa e Sousa. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .

Degree: 2012, Universidade do Rio Grande do Norte

URL: http://repositorio.ufrn.br/handle/123456789/18597

► This study proposes an observing program focused on the investigation of the stellar magnetism and dynamo evolution in cool active solar-like stars. More mainly in… (more)

Subjects/Keywords: Magnetismo estelar; Evolução; Estrelas análogas solares; Estrelas gêmeas solares; Espectropolarimetria; Stellar magnetism; Spectropolarimetric

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Duarte, T. S. e. S. (2012). Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . (Thesis). Universidade do Rio Grande do Norte. Retrieved from http://repositorio.ufrn.br/handle/123456789/18597

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Duarte, Tharcisyo Sa e Sousa. “Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .” 2012. Thesis, Universidade do Rio Grande do Norte. Accessed March 06, 2021. http://repositorio.ufrn.br/handle/123456789/18597.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Duarte, Tharcisyo Sa e Sousa. “Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .” 2012. Web. 06 Mar 2021.

Vancouver:

Duarte TSeS. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . [Internet] [Thesis]. Universidade do Rio Grande do Norte; 2012. [cited 2021 Mar 06]. Available from: http://repositorio.ufrn.br/handle/123456789/18597.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Duarte TSeS. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . [Thesis]. Universidade do Rio Grande do Norte; 2012. Available from: http://repositorio.ufrn.br/handle/123456789/18597

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Universidade do Rio Grande do Norte

5. Duarte, Tharcisyo Sa e Sousa. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .

Degree: 2012, Universidade do Rio Grande do Norte

URL: http://repositorio.ufrn.br/handle/123456789/18597

► This study proposes an observing program focused on the investigation of the stellar magnetism and dynamo evolution in cool active solar-like stars. More mainly in… (more)

Subjects/Keywords: Magnetismo estelar; Evolução; Estrelas análogas solares; Estrelas gêmeas solares; Espectropolarimetria; Stellar magnetism; Spectropolarimetric

Record Details Similar Records Cite « Share

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Duarte, T. S. e. S. (2012). Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . (Masters Thesis). Universidade do Rio Grande do Norte. Retrieved from http://repositorio.ufrn.br/handle/123456789/18597

Chicago Manual of Style (16^th Edition):

Duarte, Tharcisyo Sa e Sousa. “Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .” 2012. Masters Thesis, Universidade do Rio Grande do Norte. Accessed March 06, 2021. http://repositorio.ufrn.br/handle/123456789/18597.

MLA Handbook (7^th Edition):

Duarte, Tharcisyo Sa e Sousa. “Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria .” 2012. Web. 06 Mar 2021.

Vancouver:

Duarte TSeS. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . [Internet] [Masters thesis]. Universidade do Rio Grande do Norte; 2012. [cited 2021 Mar 06]. Available from: http://repositorio.ufrn.br/handle/123456789/18597.

Council of Science Editors:

Duarte TSeS. Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria . [Masters Thesis]. Universidade do Rio Grande do Norte; 2012. Available from: http://repositorio.ufrn.br/handle/123456789/18597

University of Florida

6. Fleck, Robert Charles, 1949-. Magnetic braking during star formation.

Degree: 1977, University of Florida

URL: https://ufdc.ufl.edu/UF00097484

Subjects/Keywords: Angular momentum; Braking; Cooling; Cosmic rays; Ionization; Magnetic fields; Magnetism; Magnets; Main sequence stars; Stellar rotation; Astronomy thesis Ph. D; Stars – Evolution; Stars – Rotation; Stars, New

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fleck, Robert Charles, 1. (1977). Magnetic braking during star formation. (Thesis). University of Florida. Retrieved from https://ufdc.ufl.edu/UF00097484

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Fleck, Robert Charles, 1949-. “Magnetic braking during star formation.” 1977. Thesis, University of Florida. Accessed March 06, 2021. https://ufdc.ufl.edu/UF00097484.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Fleck, Robert Charles, 1949-. “Magnetic braking during star formation.” 1977. Web. 06 Mar 2021.

Vancouver:

Fleck, Robert Charles 1. Magnetic braking during star formation. [Internet] [Thesis]. University of Florida; 1977. [cited 2021 Mar 06]. Available from: https://ufdc.ufl.edu/UF00097484.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Fleck, Robert Charles 1. Magnetic braking during star formation. [Thesis]. University of Florida; 1977. Available from: https://ufdc.ufl.edu/UF00097484

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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Open Access Theses and Dissertations