References of "Nazé, Yaël"
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See detailHot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newton field
Nazé, Yaël ULg; Rauw, Grégor ULg; Ud-Doula, A.

in Astronomy and Astrophysics (2010), 510

High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4-333344, and derived their spectral ... [more ▼]

High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4-333344, and derived their spectral properties for the first time. The X-ray spectrum of HD 155806 appears soft, even slightly softer than usual for O-type stars (as shown by a comparison with the O9 star HD 155889 in the same XMM-Newton field). It is well-fitted with a two-component thermal model with low temperatures (0.2 and 0.6 keV), and it shows no overluminosity (log[L_X/L_BOL] = -6.75). The high-resolution spectrum, though noisy, reveals a few broad, symmetric X-ray lines (FWHMË 2500 km s[SUP]-1[/SUP]). The X-ray emission is compatible with the wind-shock model and therefore appears unaffected by the putative dense equatorial regions at the origin of the Oe classification. 1RXS J171502.4-333344 is a nearby flaring source of moderate X-ray luminosity (log[L_X/L_BOL] = -3), with a soft thermal spectrum composed of narrow lines and presenting a larger abundance of elements (e.g. Ne) with a high first ionization potential (FIP) compared to lower-FIP elements. All the evidence indicates a coronal origin for the X-ray emission, in agreement with the dMe classification of this source. 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).Research Associate FNRS. [less ▲]

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See detailA New Investigation of the Binary HD 48099
Mahy, Laurent ULg; Rauw, Grégor ULg; Martins, F. et al

in Astrophysical Journal (2010), 708

With an orbital period of about 3.078 days, the double-lined spectroscopic binary HD 48099 is, until now, the only short-period O+O system known in the Mon OB2 association. Even though an orbital solution ... [more ▼]

With an orbital period of about 3.078 days, the double-lined spectroscopic binary HD 48099 is, until now, the only short-period O+O system known in the Mon OB2 association. Even though an orbital solution has already been derived for this system, few information are available about the individual stars. We present, in this paper, the results of a long-term spectroscopic campaign. We derive a new orbital solution and apply a disentangling method to recover the mean spectrum of each star. To improve our knowledge concerning both components, we determine their spectral classifications and their projected rotational velocities. We also constrain the main stellar parameters of both stars by using the CMFGEN atmosphere code and provide the wind properties for the primary star through the study of International Ultraviolet Explorer spectra. This investigation reveals that HD 48099 is an O5.5 V ((f)) + O9 V binary with M [SUB]1[/SUB]sin[SUP]3[/SUP] i = 0.70 M [SUB]sun[/SUB] and M [SUB]2[/SUB]sin[SUP]3[/SUP] i = 0.39 M [SUB]sun[/SUB], implying a rather low orbital inclination. This result, combined with both a large effective temperature and log g, suggests that the primary star (vsin i sime 91 km s[SUP]â 1[/SUP]) is actually a fast rotator with a strongly clumped wind and a nitrogen abundance of about 8 times the solar value. [less ▲]

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See detailObservations of nebulae ejected by massive stars with PACS
Vamvatira-Nakou, Chloi ULg; Royer, P.; Hutsemekers, Damien ULg et al

Poster (2010)

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See detailA close look at the RGS spectra of the O4Ief star Zeta Pup
Rauw, Grégor ULg; Flores, A.; Nazé, Yaël ULg et al

Poster (2010)

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See detailNumerical simulations o the wind of magnetic massive star HD191612
ud-Doula, Asif; Nazé, Yaël ULg

Diverse speeche and writing (2010)

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See detailVision multicolore de reines stellaires
Nazé, Yaël ULg

Article for general public (2010)

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See detailL'Astronomie des anciens
Nazé, Yaël ULg

Article for general public (2010)

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See detailRecherche de vie extrasolaire
Nazé, Yaël ULg

in Mémoires et Publications de la Société des Sciences, des Arts et des Lettres du Hainaut (2010), 105

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See detailL'art d'avancer masque sous une métaphore
Nazé, Yaël ULg; Gillis, P.

in Cahiers internationaux de symbolisme (2010), 125-126-127

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See detailImages de l'Univers, l'Univers en images
Nazé, Yaël ULg

in Visible (2010), 6

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See detailThe Chandra Carina Complex Project: massive stars
Gagné, M.; Fehon, G.; Dickerson, K. et al

Poster (2010)

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See detailMassive stars, a lifetime of influence
Nazé, Yaël ULg

Poster (2010)

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See detailNumerical simulations of the wind of magnetic massive star HD191612
ud-Doula, A.; Nazé, Yaël ULg

Poster (2010)

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See detailA mid-size city and IYA09: a case study
Nazé, Yaël ULg

Poster (2010)

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See detailPhase-resolved XMM-Newton observations of the massive WR+O binary WR 22
Gosset, Eric ULg; Nazé, Yaël ULg; Sana, H. et al

in Astronomy and Astrophysics (2009), 508

Aims. To better understand the phenomenon of colliding winds in massive binary stars, we study the X-ray lightcurve of a WR+O system of the Carina region, a system well known for the high mass of its ... [more ▼]

Aims. To better understand the phenomenon of colliding winds in massive binary stars, we study the X-ray lightcurve of a WR+O system of the Carina region, a system well known for the high mass of its primary.<BR /> Methods: Phase-resolved X-ray observations of the massive WR+O binary system WR 22 were performed with the XMM-Newton facility. We observed the object at seven different phases from near apastron to near periastron.<BR /> Results: The X-ray spectrum can be represented by a two-component, optically thin, thermal plasma model with a first one at a typical temperature of 0.6 keV and a second hotter one in the range 2.0-4.5 keV. The hot component is indicative of a colliding wind phenomenon, but its flux is remarkably constant with time despite the high eccentricity of the orbit. Although surprising at first, this actually does not contradict the results of the hydrodynamical simulations of the wind collision that we performed. When the system goes from apastron to periastron, the soft part of the X-ray flux is progressively lowered by an increasing intervening absorbing column. This behaviour can be interpreted in terms of an X-ray emitting plasma located near the O star, but not fully intrinsic to it, and accompanying the star when it dives into the wind of the WR component. A model is presented that interprets most of the observational constraints. This model suggests that the mass-loss rate of dot{M}[SUB]WR[/SUB] 1.6 à 10[SUP]-5[/SUP] {M}[SUB]ȯ[/SUB] yr[SUP]-1[/SUP] assumed for the WR could still be slightly too high, whereas it is already lower than other published values. From the comparison of the observed and the expected absorptions at phases near periastron, we deduce that the hard X-ray emitting collision zone should at least have a typical size of 50-60 R[SUB]ȯ[/SUB], but that the size for the soft X-ray emitting region could reach 244 R[SUB]ȯ[/SUB] if the assumed mass-loss rate is correct. We also present an upper limit to the X-ray luminosity of the WR component that further questions the existence of intrinsic X-ray emission from single WN stars.<BR /> Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). Research Associate FNRS (Belgium). Postdoctoral Researcher FNRS (Belgium). [less ▲]

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See detailUne décennie très... X!
Nazé, Yaël ULg

Article for general public (2009)

Il y a dix ans étaient lancés deux observatoires X de nouvelle génération : XMM-NEWTON (ESA) et CHANDRA (NASA). Une moisson assez extraordinaire de découvertes leur permet de révolutionner l'astronomie X ... [more ▼]

Il y a dix ans étaient lancés deux observatoires X de nouvelle génération : XMM-NEWTON (ESA) et CHANDRA (NASA). Une moisson assez extraordinaire de découvertes leur permet de révolutionner l'astronomie X, voire l'astronomie tout court, en commençant par les objets proches jusqu'à ceux des confins de l'Universe. [less ▲]

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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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