. . . . "\u00C9toiles chaudes" . "Etoiles magn\u00E9tiques" . . "About ten percent of stars with spectral type O, B or A have a detectable stable strong large-scale magnetic field at their surface, which most often resembles a magnetic dipole. These large-scale magnetic fields extend into the radiative layers of the OBA stars. Theory and simulations predict that they alter the internal structure and physical properties of these stars. In particular, it is expected that these large-scale magnetic fields enforce uniform rotation in the radiative layers and may suppress convective core overshooting. This has consequences for the evolution of these magnetic hot stars and it has implications for galactic evolution. Therefore, we observed and investigated the internal structure of magnetic hot stars. To do so, asteroseismology is the best method as the oscillation properties are directly related to the internal physical conditions. Various types of stellar oscillations are known and they are classified based on their dominant restoring force. Of these, gravity modes are governed by the buoyancy force and have their strongest probing power in the near core region, which is the domain of our interest.Our first objective was to identify pulsating magnetic hot stars and characterize their magnetic and seismic properties. We constructed a sample of magnetic candidate stars, by following indirect observational diagnostics for the presence of a large-scale magnetic field, to confirm with ground-based high-resolution optical spectropolarimetry taken with ESPaDOnS, Narval or HARPSpol. For two known magnetic stars, HD43317 and o Lup, we characterized the geometry and strength of the field in detail by analysing spectropolarimetric time series. For each star in our sample, we obtained high-cadence high-precision space-based photometry from BRITE, CoRoT, or K2 to study (periodic) variability. Only HD43317 revealed tens of stellar pulsations mode frequencies that pointed towards gravity modes. Only a few other stars studied showed a few pulsation mode frequencies, unsuitable for seismic modelling.We investigated the B3.5V star HD43317 in detail to determine the internal structure of a magnetic hot star. We did this by forward seismic modelling, where observed stellar pulsation mode frequencies in the CoRoT data covering \u223C150d were fit to those of gravito-intertial modes computed with the pulsation code GYRE, coupled to MESA stellar structure models. We identified the pulsation mode frequencies as overlapping (l, m) = (1,-1) and (2,-1) mode series. The small convective core overshooting region derived from the seismic modelling was in line with the theoretical predictions. Yet, some of the parameters for the best fitted models were also compatible with literature values for non-magnetic pulsators within the derived uncertainties. We conclude that the CoRoT time series of \u223C150d is too short to lead to stringent constraints and tests of the stellar interior to discriminate between magnetic and non-magnetic pulsating hot stars.From our detailed modelling efforts of the best studied pulsating magnetic hot star HD43317, we were unable to observationally corroborate the theoretical predictions of an altered internal structure for magnetic hot stars. Simplifications and approximations were made during the forward seismic modelling due to the limited frequency resolution of the CoRoT data in terms of its time base. Further efforts to include magnetism in the pulsation codes, or magnetism, rotation, and angular momentum transport in the evolutionary models, are worthwhile to test whether magnetic signatures are present in the numerous (non-magnetic) gravito-inertial pulsators recently found in the nominal Kepler database (which has a ten times better frequency resolution compared to CoRoT)." . "Text" . . . . . "Ast\u00E9rosismologie" . . "Environ 10% des \u00E9toiles de type spectral O, B ou A ont un champ magn\u00E9tique fort, d\u00E9tectable, stable et \u00E0 grande \u00E9chelle \u00E0 leur surface, qui ressemble le plus souvent \u00E0 un dip\u00F4le. Des mod\u00E8les th\u00E9oriques et des simulations num\u00E9riques pr\u00E9disent ces champs magn\u00E9tiques vus en surface p\u00E9n\u00E8trent aussi dans les zones radiatives et influencent la structure interne. Les mod\u00E8les pr\u00E9disent que ces champs magn\u00E9tiques imposent une rotation uniforme dans les zones radiatives et peuvent supprimer la p\u00E9n\u00E9tration convective autour du c\u0153ur. Cela a des cons\u00E9quences sur l\u2019\u00E9volution de ces \u00E9toiles chaudes magn\u00E9tiques. Pour ce faire, l\u2019ast\u00E9rosismologie est la meilleure m\u00E9thode car les param\u00E8tres des pulsations stellaires sont directement li\u00E9s aux conditions physiques internes. Plusieurs types de pulsations stellaires sont connus et class\u00E9s en fonction de leur force de rappel. Parmi eux, les plus \u00E0 m\u00EAme de sonder les r\u00E9gions proches du c\u0153ur des \u00E9toiles, sur lequel se concentre notre int\u00E9r\u00EAt dans cette th\u00E8se sont les modes de gravit\u00E9, qui sont gouvern\u00E9s par la force d\u2019Archim\u00E8de.Notre premier objectif \u00E9tait d\u2019identifier des \u00E9toiles chaudes, pulsantes et magn\u00E9tiques et de caract\u00E9riser leurs propri\u00E9t\u00E9s magn\u00E9tiques et sismiques. Des \u00E9toiles ont \u00E9t\u00E9 s\u00E9lectionn\u00E9es gr\u00E2ce \u00E0 des diagnostics observationnels indirects de la pr\u00E9sence d\u2019un champ magn\u00E9tique qou nous confirmons gr\u00E2ce \u00E0 de la spectropolarim\u00E9trie optique \u00E0 haute r\u00E9solution obtenue avec ESPaDOnS, Narval et ESPaDOnS. Pour deux \u00E9toiles magn\u00E9tiques connues, HD43317 et o Lup, nous avons caract\u00E9ris\u00E9 la g\u00E9om\u00E9trie et l\u2019intensit\u00E9 du champ magn\u00E9tique aves des s\u00E9ries temporelles spectropolarim\u00E9triques. Pour toutes les \u00E9toiles de notre \u00E9chantillon, nous avons \u00E9galement obtenu des s\u00E9ries temporelles photom\u00E9triques tr\u00E8s pr\u00E9cises gr\u00E2ce aux t\u00E9lescopes spatiaux BRITE, CoRoT ou K2 pour \u00E9tudier leur variabilit\u00E9 (p\u00E9riodique) coh\u00E9rente. Seulement HD43317 a r\u00E9v\u00E9l\u00E9 des dizaines de fr\u00E9quences de pulsations stellaires, pointant plut\u00F4t vers des modes de gravit\u00E9.Nous nous sommes ensuite concentr\u00E9s sur HD43317 dans pour d\u00E9terminer observationellement la structure interne de cette \u00E9toile magn\u00E9tique chaude. Nous avons fait usage de mod\u00E9lisation sismique: les fr\u00E9quences des modes de pulsations observ\u00E9es dans les donn\u00E9es CoRoT, couvrant 150j, ont \u00E9t\u00E9 ajust\u00E9es \u00E0 celles des modes gravito-inertiels calcul\u00E9s avec le code de pulsations GYRE coupl\u00E9 aux mod\u00E8les MESA. Nous avons pu associer les fr\u00E9quences des modes de pulsations \u00E0 des s\u00E9ries de modes (l,m) = (1,\u22121) et (2,\u22121) se chevauchant. La petite zone de p\u00E9n\u00E9tration convective dans la zone radiative telle que d\u00E9duite du mod\u00E8le MESA optimal s\u2019av\u00E8re coh\u00E9rente avec les pr\u00E9dictions th\u00E9oriques. N\u00E9anmoins, les intervalles de confiance sur certains param\u00E8tres physiques issus des mod\u00E8les sont tr\u00E8s larges et compatibles avec les valeurs de la litt\u00E9rature pour des \u00E9toiles chaudes et pulsantes mais non-magn\u00E9tiques. Nous en concluons que la s\u00E9rie temporelle de 150j de donn\u00E9es CoRoT est trop courte pour d\u00E9terminer d\u2019une mani\u00E8re non-\u00E9quivoque la structure interne des \u00E9toiles magn\u00E9tiques chaudes, et par cons\u00E9quent pour distinguer leur structure interne de celle des \u00E9toiles chaudes non-magn\u00E9tiques.Malgr\u00E9 nos efforts de mod\u00E9lisation d\u00E9taill\u00E9e de la meilleure \u00E9toile chaude pulsantemagn\u00E9tique HD43317, nous n\u2019avons pas pu corroborer observationnellement les pr\u00E9dictions th\u00E9oriques d\u2019une structure interne alt\u00E9r\u00E9e pour les \u00E9toiles chaudes magn\u00E9tiques. Des simplifications et des approximations ont d\u00FB \u00EAtre faites au cours de la mod\u00E9lisation sismique en raison de la r\u00E9solution en fr\u00E9quence limit\u00E9e des donn\u00E9es CoRoT. D\u2019autres efforts pour inclure le magn\u00E9tisme dans les codes de pulsations ou le magn\u00E9tisme, la rotation et le transfert du moment cin\u00E9tique dans les mod\u00E8les d\u2019\u00E9volution stellaire seront n\u00E9cessaires afin de d\u00E9terminer si les signatures magn\u00E9tiques sont pr\u00E9sentes pour les nombreux pulsateurs gravito-inertiels r\u00E9cemment d\u00E9couverts dans la base de donn\u00E9es de Kepler." . "\u00C9toiles -- Champs magn\u00E9tiques" . . "2018" . . "Th\u00E8ses et \u00E9crits acad\u00E9miques" . . "Magn\u00E9tisme stellaire" . "\u00C9toiles des premiers types" . . . . "\u00C9toiles pulsantes" . . . "\u00C9toiles magnetiques" . . . "Sismologie des \u00E9toiles chaudes magn\u00E9tiques" . "Sismologie des \u00E9toiles chaudes magn\u00E9tiques" . . . "Seismology of magnetic massive stars" . .