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Lefevre Laure 2006 These.Pdf (9.250Mb) Etude de la variabilité des étoiles massives à l’aide de la photométrie et de la spectroscopie par Laure Lefèvre Thèse de doctorat effectuée en cotutelle au Département de Physique Faculté des arts et des sciences Université de Montréal et à L’Observatoire Astronomique de Strasbourg Université Louis Pasteur, $trasbourg, France Thèse présentée à la faculté des études supérieures de l’Université de Montréal en vue de l’obtention du grade de Philosophiae Doctor (Ph. D.) en physique et à l’Université Louis Pasteur en vue de l’Obtention du grade de Docteur de l’Université Louis Pasteur en astrophysique Février, 2006 © Laure Lefèvre. 2006 ‘\L OCR Université de Monfréal Direction des bibliothèques AVIS L’auteur a autorisé l’Université de Montréal à reproduire et diffuser, en totalité ou en partie, par quelque moyen que ce soit et sur quelque support que ce soit, et exclusivement à des fins non lucratives d’enseignement et de recherche, des copies de ce mémoire ou de cette thèse. L’auteur et les coauteurs le cas échéant conservent la propriété du droit d’auteur et des droits moraux qui protègent ce document. Ni la thèse ou le mémoire, ni des extraits substantiels de ce document, ne doivent être imprimés ou autrement reproduits sans l’autorisation de l’auteur. Afin de se conformer à la Loi canadienne sur la protection des renseignements personnels, quelques formulaires secondaires, coordonnées ou signatures intégrées au texte ont pu être enlevés de ce document. Bien que cela ait pu affecter la pagination, il n’y a aucun contenu manquant. NOTICE The author of this thesis or dissertation has granted a nonexclusive license allowing Université de Montréal to reproduce and publish the document, in part or in whole, and in any format, solely for noncommercial educational and research purposes. The author and co-authors if applicable retain copyright ownership and moral rights in this document. Neither the whole thesis or dissertation, nor substantial extracts from it, may be printed or otherwise reproduced without the author’s permission. In compliance with the Canadian Privacy Act some supporting forms, contact information or signatures may have been removed from the document. While this may affect the document page count, it does flot represent any loss of content from the document 11 Université de Montréal Faculté des études supérieures et Observatoire astronomique de $trasbourg Université Louis Pasteur, Strasbourg Cette thèse de doctorat intitulée $ Etude de la variabilité des étoiles massives à l’aide de la photométrie et de la spectroscopie présentée et soutenue à l’Université de Montréal par: Laure Lefèvre Présentée devant le Jury composé des personnes suivantes: Pierre Bastien, président Anthony Moffat, Directeur de recherche Agnes Acker, co-directrice de recherche $ergey Marcienko, co-directeur de recherche Huib Henriclis. examinateur eerne J.-L. Halbwachs, examinateur in SOMMAIRE Mots-clés : Wolf-Rayet, vents, binarité, pulsations, satellite Les étoiles Wolf-Rayet (WR) de population I sont les descendants évolués des étoiles massives de type 0. Elles présentent de larges raies en émission produites par des atomes ionisés qui forment le vent stellaire chaud, dense et rapide. Il y a deux classes principales d’étoiles WR: les WN, où les raies de l’azote dominent, et les WC (W0) où les raies du carbone (de l’oxygène) dominent. Des observations récentes ont révelé que les vents sont “fragmentés” à petite et grande échelle, ce qui pourrait être relié en partie à des petites surdensités situées dans le vent en expansion. Cette thèse de doctorat présente la détection, l’analyse et l’interprétation, avec des outils statistiques avancés, de la variabilité dans les courbes de lumière, les vitesses radiales, et les spectres de deux étoiles WR caractéristiques (WR137 et WR123) et dans les étoiles 03 observées par le satellite HIPPARCO$. Une campagne de spectroscopie intensive a été réalisée en 1999-2000 pour améliorer notre connaissance des composantes orbitales de WR137 (WC7pd+09) et étudier les vents des WR et les conditions de formation des poussières dans de tels milieux. Le premier volet de cette thèse a permis de déduire de ces observations une orbite spec troscopique d’environ 13 ans qui confirme et précise les précédents résultats. Grâce à l’analyse des spectres de cette campagne, ce travail a mis à jour une deuxième période d’oscillation de très faible amplitude de 0.83 j dans les spectres de WR13Z. Celle-ci pourrait être reliée aux pulsations ou à de grandes structures qui tourneraient dans le vent comme dans l’étoile EZ CMa (WR6). Une analyse en ondelettes a également permis d’isoler et de suivre pendant plusieurs heures des structures en haut des raies de CIII et CIV dans le spectre de WR13Z. De plus, la corrélation croisée a permis de voir que les raies formées à différentes distances de l’étoile sont probablement reliées entre elles. Enfin l’analyse des surdentsités a permis de déduire un /3 ‘—i 5 nettement supérieur à la valeur de /3 1 que l’on trouve dans le vent des étoiles O (loi-13 de vitesse dans le vent). iv Le second volet de cette thèse concerne les étoiles WN, et plus particulièrement une WN8 du nom de WR123. Les WN8 se distinguent de leur congénères WR par plusieurs caractéristiques, dont le niveau de variabilité le plus élevé de leur classe. Du fait de ces particularités, les étoiles WN$, WR123 parmi elles, ont fait l’objet de nombreuses études photométriques et spectroscopiques. Cependant l’extrême complexité des va riations, combinée avec une couverture temporelle souvent inadaptée a conduit à une longue série de résultats ambigus. Avec les données exceptionnelles collectées par le premier satellite astronomique canadien MO$T, ce mémoire de thèse est maintenant en mesure de répondre à une grande partie des interrogations posées. L’étoile WR123 a été observée avec MOST en mode direct toutes les 30s pendant 38 jours en juin-juillet 2004. L’analyse de Fourier montre qu’aucun signal n’est stable pour plus de quelques jours dans le domaine des basses fréquences et qu’aucune variabilité significative n’est présente dans le domaine des hautes fréquences jusqu’à un niveau de 0.2 mmag, un ordre de magnitude plus bas que les prédictions pour les pulsations à modes étranges. Par contre, il semble y avoir une période de 9.8 heures présente pendant toute la durée des observations. Cette période, probablement reliée à des pulsations, pourrait permettre de mieux comprendre ce qui se passe dans les étoiles WR et leurs vents. Le troisième volet de cette thèse consiste en une analyse des différents types de variabilité des étoiles OB du catalogue HIPPARCO$. Un échantillon non biaisé de 2497 étoiles a donc été sélectionné et analysé. Il apparait que le seuil de variabilité à 99.9% établi par le consortium HIPPARCO$ n’est pas représentatif de cet échantillon. Il a donc été recalculé et les étoiles (classées dans 4 catégories principales de variabilité intrinsèque ou extrinsèque) “variables” ont été réanalysées lors de cette thèse. Ce travail a permis de confirmer des résultats obtenus à partir d’échantillons trop restreints sur les super-géantes OB, de confirmer que les étoiles OBe sont très variables ( 80%) et de soulever plusieurs questions intéressantes sur les étoiles OB de la séquence principale qui sont moins variables en moyenne. On note également plus de systèmes en contact que détachés parmi les OBMS et 03e et un nombre identique parmi les OB$G. V SUMMARY Key-words: Stars, Wolf-Rayet, Variability, Photometry, Spectroscopy, Winds, Binarity, Oscillations, Pulsations, Satellite Population I Wolf-Rayet stars are highly evolved He-burning descendents of massive OB-stars. They exhibit intense broad emission unes produced by highly-ionized atoms, which form a hot, fast and dense stellar wind. There are two broad classes of WR stars: WN, in which nitrogen unes dominate, and WC (WO), showing a dominance of carbon (oxygen) unes. Recent observations reveal that their winds are highly structured (with small or large-scale strucutres), a phenomenon which may be related in part to numerous small-scale density enhancements. This work presents the detection, analysis and interpretation, using advanced statistical tools, of the variability in photometry, radial velocities, and spectral unes of two typical WR stars (WR13Z and WR123) and in OB stars observed by the HIPPARCOS satellite. The ftrst part of this work presents the resuits of a spectroscopic study in the optical of the massive Wolf-Rayet binary WR13T (WCfpd+09). These 1986-2000 data cover the dust-formation maximum in 1997. Combining ah available measurements of radial velocities, we derive, for the first time, a spectroscopic orbit with a period of about 13 years and the corresponding orbital parameters. The analysis of the intense multi-site spectroscopic monitoring in 1999 yields a small-amplitude modulation in the absorption troughs of the CIV )5$02/12 and Hel )5876 hines with a period of 0.83 days, which could be related either to pulsations or large-scale rotating structures as seen in the WN4 star EZ Canis Majoris (WR6). Wavelet analysis of the strong emission lines of CIII )5696 and CIV )5802/12 enables us to isolate and follow for several hours smahl structures associated with density enhancements within the wind of the Wolf Rayet star. By cross-correlaaing the variability patterns seen in different unes, we find a weak but significant correlation between the varability in emission unes with different ionization potential. Adopting a 3 wind-velocity law and froua the motion of individual vi subpeaks, we find 4? 5, which is significantly larger than the canonical value t3 1 found for O-star winds. The second part of this work presents the resuits of an intensive visual-broadband photometric monitoring campaign of the highly variable WN$ Wolf-Rayet star WR123, obtained with the MOST satellite.
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