Fundamental parameters of massive stars in multiple systems: The cases of HD17505A and HD206267A

Many massive stars are part of binary or higher multiplicity systems. The present work focusses on two higher multiplicity systems: HD17505A and HD206267A. Determining the fundamental parameters of the components of the inner binary of these systems is mandatory to quantify the impact of binary or triple interactions on their evolution. We analysed high-resolution optical spectra to determine new orbital solutions of the inner binary systems. After subtracting the spectrum of the tertiary component, a spectral disentangling code was applied to reconstruct the individual spectra of the primary and secondary. We then analysed these spectra with the non-LTE model atmosphere code CMFGEN to establish the stellar parameters and the CNO abundances of these stars. The inner binaries of these systems have eccentric orbits with e ~ 0.13 despite their relatively short orbital periods of 8.6 and 3.7 days for HD17505Aa and HD206267Aa, respectively. Slight modifications of the CNO abundances are found in both components of each system. The components of HD17505Aa are both well inside their Roche lobe, whilst the primary of HD206267Aa nearly fills its Roche lobe around periastron passage. Whilst the rotation of the primary of HD206267Aa is in pseudo-synchronization with the orbital motion, the secondary displays a rotation rate that is higher. The CNO abundances and properties of HD17505Aa can be explained by single star evolutionary models accounting for the effects of rotation, suggesting that this system has not yet experienced binary interaction. The properties of HD206267Aa suggest that some intermittent binary interaction might have taken place during periastron passages, but is apparently not operating anymore.Comment: Accepted for publication in A&

Observational signatures of past mass-exchange episodes in massive binaries: The case of LSS 3074

The role of mass and momentum exchanges in close massive binaries is very important in the subsequent evolution of the components. Such exchanges produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. We investigated these effects for the close O-star binary LSS 3074 (O4 f + O6-7 :(f):), which is a good candidate for a past Roche lobe overflow (RLOF) episode because of its very short orbital period, P = 2.185 days, and the luminosity classes of both components. We determined a new orbital solution for the system. We studied the photometric light curves to determine the inclination of the orbit and Roche lobe filling factors of both stars. Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars. We then analysed the reconstructed primary and secondary spectra with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. We confirm the apparent low stellar masses and radii reported in previous studies. We also find a strong overabundance in nitrogen and a strong carbon and oxygen depletion in both primary and secondary atmospheres, together with a strong enrichment in helium of the primary star. We propose several possible evolutionary pathways through a RLOF process to explain the current parameters of the system. We confirm that the system is apparently in overcontact configuration and has lost a significant portion of its mass to its surroundings. We suggest that some of the discrepancies between the spectroscopic and photometric properties of LSS 3074 could stem from the impact of a strong radiation pressure of the primary

Observational signatures of past mass-exchange episodes in massive binaries: The case of HD 149 404

Context. Mass and momentum exchanges in close massive binaries play an important role in their evolution, and produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. Aims: We investigated these effects for the detached massive O-star binary HD 149 404 (O7.5 If + ON9.7 I, P = 9.81 days), which is thought to have experienced a past episode of case A Roche-lobe overflow (RLOF). Methods: Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars. The reconstructed primary and secondary spectra were then analysed with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. We complemented the optical study with the study of IUE spectra, which we compare to the synthetic binary spectra. The properties of the stars were compared to evolutionary models. Results: We confirmed a strong overabundance in nitrogen ([N/C] ~ 150[N/C][SUB]⊙[/SUB]) for the secondary and a slight nitrogen overabundance ([N/C] ~ 5[N/C][SUB]⊙[/SUB]) for the primary star. Comparing the two stars, we found evidence for asynchronous rotation, with a rotational period ratio of 0.50 ± 0.11. Conclusions: The hypothesis of a past case A RLOF interaction in HD 149 404 is most plausible to explain its chemical abundances and rotational asynchronicity. Some of the observed properties, such as the abundance pattern, are clearly a challenge for current case A binary evolution models, however.ARC - Actions de recherche concertées; Etoiles massive

Terminological challenges in the translation of science documentaries: a case-study

This article aims to describe some of the main terminological problems audiovisual translators have to face when dealing with the translation of science documentaries, specifically in the English-Catalan combination. The first section of the article presents some theoretical concepts which underlie this research and which are taken, for the most part, from Cabré's Communicative Theory of Terminology. Then, specific terminological problems audiovisual translators have to solve are described using the data provided by a corpus of four science documentaries lasting approximately 50 minutes each. These challenges include identifying a term, understanding a term, finding the right equivalent, dealing with the absence of an adequate equivalent, solving denominative variations, choosing between in vivo and in vitro terminology, and overcoming mistranscriptions

Sociétés anonymes /

Mis à jour au 15 juin 1981 / Par Gilberte Rauc

Search for the signatures of mass-exchange episodes in massive binaries

Massive stars are known for their crucial role in our Universe, through their extreme stellar parameters, leading to a strong impact on their environment. However, there remain numbers of unanswered questions concerning the exact processes of their formation, their stability or the processes driving their strong stellar winds. In the context of this thesis work, we adress one of the most interesting of their peculiarities: their tendency to be part of binary of higher multiplicity systems. Whilst this multiplicity does help to solve some open issues by allowing us to study some of the fundamental properties of the stars, such as their minimum masses and radii as well as their stellar luminosities, it can also lead to interactions between the components of a system, which affect the subsequent evolution of the stars and give rise to additional open questions on the processes in place in such systems. Among the possible interactions taking place within close binary systems is the possibility of a transfer of mass and kinetic momentum through a Roche lobe overflow. This process has a huge impact on the subsequent evolution of both components and many aspects of this phenomenon are not well understood yet. The present work is devoted to the search for the signatures of such past mass-exchange episodes in a sample of four short-period massive multiple systems: HD 149404, LSS 3074, HD 17505 and HD 206267. We determined a new orbital solution for three of them. We then used phase-resolved spectroscopy to perform the spectral disentangling of the optical spectra of the components. The spectral disentangling is a mathematical tool which allows to separate the contributions of both components to the observed spectra of a system. We then analysed the reconstructed spectra with the CMFGEN atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the surface chemical composition of each component. The first two parts of this dissertation are dedicated to the scientific background and the description of the numerical tools and methods used in this work. The third part presents our studies of the selected massive systems. We confirmed that the hypothesis of a past Roche lobe overflow episode is most plausible to explain the observed properties of the components of HD 149404. Photometric data permitted us to confirm that LSS 3074 is in an overcontact configuration, and a combined analysis with spectroscopy showed that the system has lost a significant fraction of its mass to its surroundings. We proposed several possible evolutionary pathways involving a Roche lobe overflow process to explain the current parameters of its components. We found no evidence of past mass-transfer episodes in the spectra of HD 17505 and showed that the current properties of its components can be explained by single star evolutionary models including rotational mixing. We found clues of binary interactions in the spectra of HD 206267, but suggested that the system did not experience a complete Roche lobe overflow episode at this stage of its evolution

Influence de la géométrie sur la substitution captodative: étude comparative de radicaux, d'anions et d'oléfines à substitution captodative ouverte ou cyclique

Doctorat en Sciences chimiques -- UCL, 199

Hutcheon (Linda). Narcissistic Narrative. The Metaflctional Paradox

Raucq-Hoorickx I. Hutcheon (Linda). Narcissistic Narrative. The Metaflctional Paradox. In: Revue belge de philologie et d'histoire, tome 63, fasc. 3, 1985. Langues et littératures modernes — Moderne taal- en letterkunde. pp. 599-602

Business plan en vue de la création d'un bar à sushis

Mémoire de Master [120] en sciences de gestion (horaire décalé), Université catholique de Louvain, 201