References of "Nazé, Yaël"
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See detailEuroPlaNet is celebrating a very special year
Chatzchristou, E. T.; Nazé, Yaël ULg

Poster (2007)

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See detailNGC6231: X-ray Properties of the Early-Type Star Population
Sana, H.; Nazé, Yaël ULg; Gosset, Eric ULg et al

in Massive Stars in Interactive Binaries (2007)

Based on a deep XMM-Newton observation of the young open cluster NGC6231, we derive the main X-ray properties of its early-type star population. Among the 610 X-ray sources detected in the field, 42 are ... [more ▼]

Based on a deep XMM-Newton observation of the young open cluster NGC6231, we derive the main X-ray properties of its early-type star population. Among the 610 X-ray sources detected in the field, 42 are associated with early-type stars. We investigate their L[SUB]X[/SUB]/L[SUB]bol[/SUB] relationship and confirm the clear dichotomy between O- and B-type stars. The cut-off line between the two behaviours occurs at L[SUB]bol[/SUB] ~ 10[SUP]38[/SUP] erg s[SUP]-1[/SUP] as previously proposed by Berghöfer et al. (1997). The distinction between single and binary stars is not clear cut, except for the colliding wind system HD152248. The X-ray detected B-stars in NGC6231 appear to be more luminous than predicted from the Berghöfer et al. relation. Though this suggests a bimodal distribution of the B-star X-ray emission, we caution however that these results might be biased by detection limits. Finally we investigate the X-ray variability of the detected sources and we find that about 40% of the X-ray emitters in the field of view present consistent signs of variability in the EPIC instruments. This fraction is much larger than previously thought. About one third of the early-type star population, either singles or binaries, further show variability. These variations do not seem to be exclusively related to binarity and could thus not be systematically interpreted in the framework of a wind-wind collision phenomenon. [less ▲]

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See detailThe first orbital solution for the massive colliding-wind binary HD 93162 ( WR 25)
Gamen, R.; Gosset, Eric ULg; Morrell, N. et al

in Astronomy and Astrophysics (2006), 460(3), 777-782

Context. Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD 93162 (equivalent to WR 25), this object has been predicted to be a colliding-wind binary system ... [more ▼]

Context. Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD 93162 (equivalent to WR 25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the suspected binary nature have yet to be found. Aims. We spectroscopically monitored this object to investigate its possible variability to address this discordance. Methods. We compiled the largest available radial-velocity data set for this star to look for variations that might be due to binary motion. We derived radial velocities from spectroscopic data acquired mainly between 1994 and 2006, and searched these radial velocities for periodicities using different numerical methods. Results. For the first time, periodic radial-velocity variations are detected. Our analysis definitively shows that the Wolf-Rayet star WR 25 is an eccentric binary system with a probable period of about 208 days. [less ▲]

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See detailAn XMM-Newton view of the young open cluster NGC 6231 - II. The OB star population
Sana, H.; Rauw, Grégor ULg; Nazé, Yaël ULg et al

in Monthly Notices of the Royal Astronomical Society (2006), 372(2), 661-678

In this second paper of the series, we pursue the analysis of the 180-ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature ... [more ▼]

In this second paper of the series, we pursue the analysis of the 180-ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature-based census of the OB stars in the field of view with more than one hundred objects, among which 30 per cent can be associated with an X-ray source. All the O-type stars are detected in the X-ray domain as soft and reasonably strong emitters. In the 0.5-10.0 keV band, their X-ray luminosities scale with their bolometric luminosities as log L-X - log L-bol = -6.912 +/- 0.153. Such a scaling law holds in the soft (0.5-1.0 keV) and intermediate (1.0-2.5 keV) bands but breaks down in the hard band. While the two colliding wind binaries in our sample clearly deviate from this scheme, the remaining O-type objects show a very limited dispersion (40 or 20 per cent according to whether 'cool' dwarfs are included or not), much smaller than that obtained from previous studies. At our detection threshold and with our sample, the sole identified mechanism that produces significant modulations in the O star X-ray emission is related to wind interaction. We thus propose that the intrinsic X-ray emission of non-peculiar O-type stars can be considered as constant for a given star. In addition, the level of X-ray emission is accurately related to the star luminosity or, equivalently, to its wind properties. Among B-type stars, the detection rate is only about 25 per cent in the subtype range B0-B4 and remains mostly uniform throughout the different subpopulations while it drops significantly at later subtypes. The associated X-ray spectra are harder than those of O-type stars. Our analysis points towards the detected emission being associated with a physical (in a multiple system) PMS companion. However, we still observe a correlation between the bolometric luminosity of the B stars and the measured X-ray luminosity. The best-fitting power law in the 0.5-10.0 keV band yields log L-X = 0.22(+/- 0.06) log L-bol + 22.8(+/- 2.4). [less ▲]

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See detailVera Rubin, la femme qui a changé la face de l'Univers
Nazé, Yaël ULg

Article for general public (2006)

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See detailThe atypical emission-line star Hen 3-209
Nazé, Yaël ULg; Rauw, Grégor ULg; Hutsemekers, Damien ULg et al

in Monthly Notices of the Royal Astronomical Society (2006), 371(4), 1594-1600

We analyse observations, spanning 15 yr, dedicated to the extreme emission-line object Hen 3-209. Our photometric data indicate that the luminosity of the star undergoes marked variations with a peak-to ... [more ▼]

We analyse observations, spanning 15 yr, dedicated to the extreme emission-line object Hen 3-209. Our photometric data indicate that the luminosity of the star undergoes marked variations with a peak-to-peak amplitude of 0.65 mag. These variations are recurrent, with a period of 16.093 +/- 0.005 d. The spectrum of Hen 3-209 is peculiar with many different lines (H I, He I, Fe II,. showing P Cygni profiles. The line profiles are apparently changing in harmony with the photometry. The spectrum also contains [O III] lines that display a saddle profile topped by three peaks, with a maximum separation of about 600 km s(-1). Hen 3-209 is most likely an evolved luminous object suffering from mass ejection events and maybe belonging to a binary system. [less ▲]

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See detailL'univers des Hautes Energies dévoilé par Integral
Nazé, Yaël ULg; Rauw, Grégor ULg

Article for general public (2006)

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See detailHigh Resolution X-ray Spectroscopy of Early-Type Stars
Rauw, Grégor ULg; Pollock, A. M. T.; Nazé, Yaël ULg

in High Resolution X-ray Spectroscopy: towards XEUS and Con-X (2006, August 01)

Although X-ray emission from massive, early-type stars has been known for almost thirty years, it is only with the advent of the high-resolution spectrographs aboard Chandra and XMM-Newton that a detailed ... [more ▼]

Although X-ray emission from massive, early-type stars has been known for almost thirty years, it is only with the advent of the high-resolution spectrographs aboard Chandra and XMM-Newton that a detailed investigation of the X-ray spectra of these stars has become possible. The existing observations of both single and binary early-type stars have been used to study the properties of their stellar winds. While some results agree with the expectations from theoretical models, other spectra show unexpected features. In this contribution, we review our current knowledge on the X-ray emission of stars of spectral type O and Wolf-Rayet and discuss the possibilities to test some new ideas with future high-resolution X-ray observations. [less ▲]

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See detailRecords stellaires
Nazé, Yaël ULg

Article for general public (2006)

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See detailRévélations cosmiques - l'astronomie TeV prend son envol
Nazé, Yaël ULg

Article for general public (2006)

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See detailLive fast, die young
Nazé, Yaël ULg

Article for general public (2006)

Massive stars: How far away are they? How do they form? What is a star's maximum mass? What role did they play after the big bang? How do massive binaries form? Can planets form around massive stars? What ... [more ▼]

Massive stars: How far away are they? How do they form? What is a star's maximum mass? What role did they play after the big bang? How do massive binaries form? Can planets form around massive stars? What role do rotation and magnetic fields play? How do massive single and binaries evolve? How do they die? [less ▲]

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See detailNew light on the peculiar star HD108
Nazé, Yaël ULg; Barbieri, C.; Segafredo, A. et al

in Information Bulletin on Variable Stars (2006), 5693

HD 108 is a peculiar massive star of type Of?p, which present recurrent line profile variations. Archival data confirm the very long (50-60 yr) period of this star. Recent data show that the minimum state ... [more ▼]

HD 108 is a peculiar massive star of type Of?p, which present recurrent line profile variations. Archival data confirm the very long (50-60 yr) period of this star. Recent data show that the minimum state is not yet reached. [less ▲]

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See detailL'astronomie au féminin
Nazé, Yaël ULg

Book (2006)

Qui détient le record des découvertes de comètes ? Une femme. Qui a permis de comprendre comment est organisée la population des étoiles ? Une femme. Qui a découvert la loi permettant d'arpenter l'Univers ... [more ▼]

Qui détient le record des découvertes de comètes ? Une femme. Qui a permis de comprendre comment est organisée la population des étoiles ? Une femme. Qui a découvert la loi permettant d'arpenter l'Univers, a trouvé des phares dans l'espace, a compris le fonctionnement des forges stellaires et a bouleversé notre vision de l'Univers ? Encore et toujours une femme... Pourtant, quand on doit citer un astronome -- historique -- au hasard, on pense le plus souvent -- des hommes : Ptolémée, Galilée, Copernic ou, plus prè de nous par exemple, Hubble. Certes, au cours des siècles, les femmes n'ont guère eu accè aux sciences en général et -- l'astronomie en particulier mais ce n'est pas une raison pour croire en l'absence totale de contributions dues au beau sexe ! C'est ce que dévoile ici l'auteur. Loin de toute forme de féminisme enragé, on suivra le parcours de quelques scientifiques importantes qui ont par hasard en commun une même particularité : leur sexe. [less ▲]

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See detailLe ciel selon XMM-Newton
Rauw, Grégor ULg; Nazé, Yaël ULg

Article for general public (2006)

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See detailLa merveilleuse cannibale
Nazé, Yaël ULg

Article for general public (2006)

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See detailThe Peculiar Of?p Stars HD 108 and HD 191612: The X-ray View
Nazé, Yaël ULg; Rauw, Grégor ULg; Walborn, N. R. et al

in The X-ray Universe 2005 (2006, January 01)

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See detailSpectroscopy of Massive Stars
Nazé, Yaël ULg

in Bulletin de la Société Royale des Sciences de Liège (2006), 75

Although rare, massive stars, being the main sources of ionizing radiation, chemical enrichment and mechanical energy in the Galaxy, are the most important objects of the stellar population. This review ... [more ▼]

Although rare, massive stars, being the main sources of ionizing radiation, chemical enrichment and mechanical energy in the Galaxy, are the most important objects of the stellar population. This review presents the many different aspects of the main tool used to study these stars, i.e. spectroscopy. The first part consists in an introduction on these objects and their physical properties (mass, wind, evolution, relation with their environment). Next, the spectral behaviour of single massive stars is investigated, in the visible as well as in the X-ray domain. Finally, the last part of this paper deals with massive binaries, especially those exhibiting a colliding wind phenomenon. [less ▲]

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See detailPhase-resolved observations of a peculiar O star
Nazé, Yaël ULg

Poster (2006)

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See detailAn outreach experience
Nazé, Yaël ULg

in European Planetary Science Congress 2006 (2006)

In our technological world, Science is everywhere and to participate to the public debates, citizens will need some basic scientific notions. Raising awareness of the public in Science is thus always ... [more ▼]

In our technological world, Science is everywhere and to participate to the public debates, citizens will need some basic scientific notions. Raising awareness of the public in Science is thus always worthwhile, even though only a small fraction of the audience will envisage a career in the field. Bringing science to the layman should even be a duty for scientists: we should not forget that we are paid by taxpayers, and are part of a public service; and besides, people tend to reject things that they do not understand - to get support, scientists need to enter the public arena and confront the crowd. Relying on attractive images and a timeless fascination, astronomy is particularly suited to do that. But what should a willing astronomer do to share (his/her) knowledge? There is certainly no definitive answer for that, but a few hints can still be given. Based on personal experience, this talk will present a few tips and things to avoid in three cases: animations (for kids and grown-ups), writing, and talking. [less ▲]

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See detailLe chemin céleste à travers les âges
Nazé, Yaël ULg

Article for general public (2005)

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