References of "Nazé, Yaël"
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See detailHot stars observed by XMM-Newton. I. The catalog and the properties of OB stars
Nazé, Yaël ULg

in Astronomy and Astrophysics (2009), 506

Aims: Following the advent of increasingly sensitive X-ray observatories, deep observations of early-type stars became possible. However, the results for only a few objects or clusters have until now been ... [more ▼]

Aims: Following the advent of increasingly sensitive X-ray observatories, deep observations of early-type stars became possible. However, the results for only a few objects or clusters have until now been reported and there has been no large survey comparable to that based upon the ROSAT All-Sky Survey (RASS). <BR />Methods: A limited survey of X-ray sources, consisting of all public XMM-Newton observations (2XMMi) and slew survey data (XMMSL1), is now available. The X-ray counterparts to hot, massive stars have been searched for in these catalogs. <BR />Results: About 300 OB stars were detected with XMM-Newton. Half of them were bright enough for a spectral analysis to be possible, and we make available the detailed spectral properties that were derived. The X-ray spectra of O stars are represented well by low (<1 keV) temperature components and seem to indicate that an absorption column is present in addition to the interstellar contribution. The X-ray fluxes are well correlated with the bolometric fluxes, with a scatter comparable to that of the RASS studies and thus larger than found previously with XMM-Newton for some individual clusters. These results contrast with those of B stars that exhibit a large scatter in the L[SUB]X[/SUB] - L[SUB]BOL[/SUB] relation, no additional absorption being found, and the fits indicate a plasma at higher temperatures. Variability (either within one exposure or between multiple exposures) was also investigated whenever possible: short-term variations are far more rare than long-term ones (the former affects a few percent of the sample, while the latter concerns between one third and two thirds of the sources). <BR />Conclusions: This paper presents the results of the first high-sensitivity investigation of the overall high-energy properties of a sizable sample of hot stars. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), and accessed via the 2XMMi and XMM slew survey catalogs. Tables 1 and 5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/1055 Postdoctoral Researcher FNRS. Visiting astronomer, UNAM-Morelos (Mexico). [less ▲]

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See detailX-ray spectroscopy of stars
Guedel, Manuel; Nazé, Yaël ULg

in Astronomy and Astrophysics Review (2009), 17

Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Their X-ray spectra have been important in constraining physical processes that heat plasma in stellar environments to ... [more ▼]

Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Their X-ray spectra have been important in constraining physical processes that heat plasma in stellar environments to temperatures exceeding one million degrees. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. The Sun itself as a typical example of a main-sequence cool star has been a pivotal testbed for physical models to be applied to cool stars. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma, although plasma parameters such as temperature, density, and element abundances vary widely. Coronal structure, its thermal stratification and geometric extent can also be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechanical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind. Medium and high- resolution spectroscopy have shed new light on these objects as well. Here, we review recent advances in our understanding of cool and hot stars through the study of X-ray spectra, in particular high-resolution spectra now available from XMM -Newton and Chandra. We address issues related to coronal structure, flares, the composition of coronal plasma, X-ray production in accretion streams and outflows, X-rays from single OB-type stars, massive binaries, magnetic hot objects and evolved WR stars. [less ▲]

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See detailOptical spectroscopy of X-Mega targets in the Carina nebula - VII. On the multiplicity of Tr16-112, HD93343 and HD93250
Rauw, Grégor ULg; Nazé, Yaël ULg; Fernández Lajús, E. et al

in Monthly Notices of the Royal Astronomical Society (2009), 398

We present the results of a spectroscopic monitoring campaign devoted to three O-type stars in the Carina nebula. We derive the full SB2 orbital solution of the binary system Tr16-112, an exceptional ... [more ▼]

We present the results of a spectroscopic monitoring campaign devoted to three O-type stars in the Carina nebula. We derive the full SB2 orbital solution of the binary system Tr16-112, an exceptional dissymmetrical system consisting of an O5.5-6V((f[SUP]+[/SUP]?p)) primary and a B2V-III secondary. We also report on low-amplitude brightness variations in Tr16-112 that are likely due to the ellipsoidal shape of the O5.5-6 primary revolving in an eccentric orbit around the system's centre of mass. We detect for the first time a clear SB2 binary signature in the spectrum of HD93343 (O8 + O8), although our data are not sufficient to establish an orbital solution. This system also displays low-amplitude photometric modulations. On the other hand, no indication of multiplicity is found in the optical spectra of HD93250. Finally, we discuss the general properties of multiple massive stars in the Carina OB1 association. Based on observations collected at the European Southern Observatory (La Silla, Chile), at Complejo Astronómico El Leoncito (Argentina), at the Cerro Tololo Inter-American Observatory (CTIO) and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). E-mail: rauw@astro.ulg.ac.be â ¡ Research Associate FRS/FNRS (Belgium). § Postdoctoral Researcher FRS/FNRS (Belgium). ¶ Senior Research Associate FRS/FNRS (Belgium). [less ▲]

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See detailEarly-type stars in the young open cluster NGC 2244 and in the Monoceros OB2 association. I. The multiplicity of O-type stars
Mahy, Laurent ULg; Nazé, Yaël ULg; Rauw, Grégor ULg et al

in Astronomy and Astrophysics (2009), 502

Aims. We present the results obtained from a long-term spectroscopic campaign to study the multiplicity of O-type stars in both the young open cluster NGC 2244 and the Mon OB2 association. Methods: Our ... [more ▼]

Aims. We present the results obtained from a long-term spectroscopic campaign to study the multiplicity of O-type stars in both the young open cluster NGC 2244 and the Mon OB2 association. Methods: Our spectroscopic monitoring was performed over several years, allowing us to investigate different timescales. For each star, several spectral diagnostic tools were applied to search for line shifts and profile variations. We also measured the projected rotational velocity and revisited the spectral classification. Results: Several stars in our sample have been previously considered to be spectroscopic binaries, although only a few scattered observations were available. Our results now have identified a more complex situation for two new spectroscopic binaries (HD 46 149 in NGC 2244 and HD 46 573 in Mon OB2). The first object is a long-period double-lined spectroscopic binary, although the exact value of its period remains uncertain and the second object is classified as an SB1 system with a period of about 10.67 days but the time series of our observations do not enable us to derive a unique orbital solution for this system. We also find another star to be variable in radial velocity (HD 46 150) and detect line profile variations in two rapid rotators (HD 46 056 and HD 46 485). Conclusions: This spectroscopic investigation places a firm lower limit (17%) on the binary fraction of O-stars in NGC 2244 and reveals the lack of short-period O+OB systems in this cluster. In addition, a comparison of these new results with two other well-studied clusters (NGC 6231 and IC 1805) puts forward possible hints of a relation between stellar density and binarity, which could provide constraints on the theories of the formation and early evolution of hot stars. Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/937 Based on observations collected at Observatoire de Haute-Provence (France), San Pedro Màrtir Observatory (Mexico), La Silla Observatory (European Southern Observatory), and Asiago Observatory (Italy). [less ▲]

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See detailLes étoiles massives, ces reines de l'Univers
Nazé, Yaël ULg

Article for general public (2009)

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See detailA la poursuite de l'etoile-record
Nazé, Yaël ULg

Article for general public (2009)

Not Available

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See detailTélescopes d'aujourd'hui - les instruments professionnels
Nazé, Yaël ULg

Article for general public (2009)

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See detailL'astronomie des Anciens
Nazé, Yaël ULg

Book published by belin (2009)

Quelle que soit la civilisation à laquelle il appartient, l'etre humain cherche dans le ciel des réponses aux questions qu'il se pose sur son origine, son avenir et sa finalité. Le premier mérite de ce ... [more ▼]

Quelle que soit la civilisation à laquelle il appartient, l'etre humain cherche dans le ciel des réponses aux questions qu'il se pose sur son origine, son avenir et sa finalité. Le premier mérite de ce livre est de nous rappeler que l'astronomie a commencé ainsi à travers les mythes célestes imaginés par les Anciens pour expliquer l'ordre du monde et la place qu'ils y occupaient. Mais les savoirs astronomiques passés étaient loin d'etre négligeables et certainement pas limités aux seuls travaux des Grecs : c'est ce que l'auteur montre à travers une passionnante enquete, de Stonehenge à Gizeh en passant par Pékin et Mexico, fondée sur l'étude des monuments anciens et des sources écrites encore accessibles. Les tablettes mésopotamiennes, les annales chinoises, les chroniques médiévales, etc. sont en outre d'une singulière utilité pour les astronomes modernes : comment sinon remonter aux variations de la durée du jour au cours des siècles, ou percer la nature de l'explosion qui a frappé tant d'observateurs en 1054 ? Ce livre offre un voyage magnifiquement illustré à travers les âges, entre astronomie et archéologie. [less ▲]

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See detailcahier d'exploration du ciel
Nazé, Yaël ULg

Book published by Réjouisciences (2009)

Ce cahier, conçu par Yaël Nazé, astrophysicienne à l'Université de Liège, vous emmène à la découverte de notre Univers. Vous y voyagerez dans le temps et l'espace, comprendrez le pourquoi des saisons sur ... [more ▼]

Ce cahier, conçu par Yaël Nazé, astrophysicienne à l'Université de Liège, vous emmène à la découverte de notre Univers. Vous y voyagerez dans le temps et l'espace, comprendrez le pourquoi des saisons sur Terre et des phases de la Lune, explorerez notre Système solaire et la voûte céleste constellée d'étoiles, et lancerez finalement des fusées ! Les notions astronomiques de base sont expliquées grâce à un texte clair, des images vivantes, et surtout, via une douzaine d'expériences réalisables avec du matériel facile à trouver (oranges, lampes de poche, carton,...). A la fin, divers exercices sont proposés pour récapituler les connaissances acquises : ils touchent tant aux compétences en français qu'aux compétences en sciences ou en mathématiques. Ce cahier multidisciplinaire est accessible à tous et particulièrement destiné aux 10-15 ans et à leurs enseignants. [less ▲]

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See detailThe X-ray stellar population of the LMC
Nazé, Yaël ULg

in IAU Symposium (2009, March 01)

In the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive ... [more ▼]

In the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC. [less ▲]

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See detail1609, la révolution de l'observation
Nazé, Yaël ULg

Article for general public (2009)

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See detailHistoire du télescope, la contemplation de l'Univers, des premiers instruments aux actuelles machines célestes
Nazé, Yaël ULg

Book (2009)

Alors que la plupart des scientifiques réalisent leurs expérimentations en laboratoire, les astronomes sont condamnés à ne jamais pouvoir toucher l'objet de leurs travaux: le ciel se laisse contempler ... [more ▼]

Alors que la plupart des scientifiques réalisent leurs expérimentations en laboratoire, les astronomes sont condamnés à ne jamais pouvoir toucher l'objet de leurs travaux: le ciel se laisse contempler mais demeure hors d'atteinte. Pour déchiffrer le message céleste, l'oeil ne suffit pas. Il fallut attendre la naissance de la première lunette astronomique pour ouvrir une nouvelle voie à notre insatiable désir de savoir. Ancêtre de tous les télescopes petits et grands, ce tout premier instrument d'observation allait en effet étendre vers l'infini le pouvoir de nos yeux. Quatre cents ans aprè, ce sont d'immenses machines qui scrutent pour nous l'Univers, en nous permettant même de remonter le temps. C'est leur histoire qui nous est racontée ici mais, par deça les engins les plus complexes, ce livre nous parle de leurs bâtisseurs. Démontant au passage certaines idées reçues, ce livre nous plonge dans les balbutiements de ces instruments avant de nous emmener côtoyer les premiers géants et découvrir les révolutions en cours. Illustré de nombreux documents historiques et techniques, ce récit est également pourvu d'encadrés expliquant en profondeur le fonctionnement des instruments. [less ▲]

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See detailAurores, les lumières atmosphériques
Nazé, Yaël ULg

Article for general public (2009)

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See detailLunettes et télescopes, l'Univers se dévoile
Jaminon, Martine ULg; Nazé, Yaël ULg; Taton, Fabrice

Learning material (2009)

Plaquette de l'exposition "Lunettes et Télescopes : l'Univers se dévoile" + animations flash illustrant la réflexion par des miroirs sphériques et la réfraction par des lentilles divergentes et ... [more ▼]

Plaquette de l'exposition "Lunettes et Télescopes : l'Univers se dévoile" + animations flash illustrant la réflexion par des miroirs sphériques et la réfraction par des lentilles divergentes et convergentes. [less ▲]

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See detailAstronomie et religion
Nazé, Yaël ULg

Article for general public (2009)

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See detailLes planètes
Nazé, Yaël ULg

Article for general public (2009)

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See detailThe Europlanet national nodes network
Fouchet, T.; Heward, A.; Chatzchristou, E. T. et al

Poster (2009)

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See detailThe strange case of the Of?p stars
Nazé, Yaël ULg; Walborn, N. R.; Martins, F. et al

Poster (2009)

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See detailHot stars survey with the GAIA space mission
Lobel, A.; Liu, C.; Frémat, Y. et al

Poster (2009)

Detailed reference viewed: 13 (7 ULg)
See detailEmission line stars in the Milky Way with the GAIA space mission
Martayan, C.; Frémat, Y.; Blomme, R. et al

Poster (2009)

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