References of "Nazé, Yaël"
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See detailThe multiwavelength view of hot, massive stars
Rauw, Grégor ULg; De Becker, Michaël ULg; Nazé, Yaël ULg et al

in Bulletin de la Société Royale des Sciences de Liège (2011), 80

Massive stars are certainly among the most fascinating objects of stellar populations. They trigger many astrophysical processes from star formation to the chemical enrichment of the interstellar medium ... [more ▼]

Massive stars are certainly among the most fascinating objects of stellar populations. They trigger many astrophysical processes from star formation to the chemical enrichment of the interstellar medium. Yet, their properties are still not fully understood and these objects are therefore at the core of many ongoing research activities. With the advent of new, high-performance, ground-based and space-borne facilities, the multi-wavelength investigation of hot, massive stars has definitely been boosted over the last decade. It is indeed nowadays possible to study these objects over a wide part of the electromagnetic spectrum, all the way from radio waves to gamma-rays. Motivated by this fact, we decided to organize a conference devoted to this topic in the framework of the well-established series of Liege International Astrophysical Colloquia (LIAC). The resonance in the community was extremely positive, with many proposals for high-quality contributions. During the week of 12 - 16 July 2010, 138 astrophysicists, from institutes in 21 countries all over the world, gathered in Liege to discuss how the multi-wavelength approach has revolutionized their research on massive stars. The colloquium was organized into five thematic sessions, and the present proceedings are organized along the same chapters: (1) stellar winds, diagnostics across the electromagnetic spectrum; (2) massive star formation, confronting theory and observation; (3) evolution and interaction of massive stars with their environment; (4) future instrumentation and its application to massive star research; (5) massive binaries: interaction and evolution. [less ▲]

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See detailMassive non-thermal radio emitters: new data and their modelling
Volpi, D.; Blomme, R.; De Becker, Michaël ULg et al

Poster (2011)

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See detailThe Herschel view of nebulae around evolved massive stars
Vamvatira Nakou, Chloi ULg; Royer, P.; Hutsemekers, Damien ULg et al

Conference (2011)

The detailed study of the nebulae ejected from Luminous Blue Variables and the circumstellar bubbles around Wolf-Rayet stars, which radiate strongly in the IR due to the heating of dust, is crucial for ... [more ▼]

The detailed study of the nebulae ejected from Luminous Blue Variables and the circumstellar bubbles around Wolf-Rayet stars, which radiate strongly in the IR due to the heating of dust, is crucial for understanding the massive stars evolution. With Herschel, the largest telescope ever flown in space, we are able to study the gas and the dust in these circumstellar environments in the full far-infrared waveband. In the context of 'Mass-loss of Evolved StarS' Herschel guaranteed time key programme, we have obtained imaging and spectroscopic observations of nebulae associated with Luminous Blue Variable and Wolf-Rayet stars using PACS, one of the three instruments onboard Herschel. A description of these observations and first results of the data analysis are presented. [less ▲]

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See detailResults from the Herschel Key Program MESS
Groenewegen, M. A. T.; Waelkens, C.; Barlow, M. J. et al

in Kerschbaum, F.; Lebzelter, T.; Wing, R. F. (Eds.) Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants. ASPC 445 (2011)

MESS (Mass loss of Evolved StarS) is a Herschel Guaranteed Time Key Program that will image about 100, and do spectroscopy of about 50, post-main-sequence objects of all flavours: AGB stars, post-AGB ... [more ▼]

MESS (Mass loss of Evolved StarS) is a Herschel Guaranteed Time Key Program that will image about 100, and do spectroscopy of about 50, post-main-sequence objects of all flavours: AGB stars, post-AGB stars, planetary nebulae, luminous blue variables, Wolf-Rayet stars, and supernova remnants. In this review the implementation and current status of MESS is outlined, and first results are presented. [less ▲]

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See detailLe ciel est bleu comme une horloge...
Nazé, Yaël ULg

Article for general public (2011)

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See detailLe centre, les planètes et la noirceur : Controverses cosmiques et terrestres
Nazé, Yaël ULg

Article for general public (2011)

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See detailA Chandra search for low-mass companions of late B-stars in Tr16
Evans, N. R.; DeGioia-Eastwood, K.; Gagné, M. et al

Poster (2011)

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See detailPlasma Motion and Kinematics in Cool and Hot Stars
Güdel, Manuel; Nazé, Yaël ULg

in Space Science Reviews (2010), 157

The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams ... [more ▼]

The environments of both hot and cool stars are the sites of highly dynamic processes involving motion of gas and plasma in winds, flows across shocks, plasma motions in closed magnetic fields, or streams along magnetospheric accretion funnels. X-ray spectroscopy has opened new windows toward the study of these processes. Kinematics are evident in line shifts and line broadening, and also more indirectly through the analysis and interpretation of density-sensitive lines. In hot stellar winds, expanding-wind kinematics are directly seen in broadened lines although the broadening has turned out to often be smaller than anticipated, and some lines are so narrow that coronal models have been revived. Although X-ray spectra of cool stars have shown line shifts and broadening due to the kinematics of the entire corona, e.g., in binary systems, intrinsic mass motions are challenging to observe at the presently available resolution. Much indirect evidence for mass motion in magnetic coronae is nevertheless available. And finally, spectral diagnostics has also led to a new picture of X-ray production in accreting pre-main sequence stars where massive accretion flows collide with the photospheric gas, producing shocks in which gas is heated to high temperatures. We summarize evidence for the above mechanisms based on spectroscopic data from XMM-Newton and Chandra. [less ▲]

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See detailPanorama des couleurs de l'univers
Nazé, Yaël ULg

Article for general public (2010)

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See detailUne course aux limites des télescopes - étudier en détail une exoplanète
Nazé, Yaël ULg

Article for general public (2010)

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See detailPetit mais costaud: une nouvelle façon de voir les planètes
Nazé, Yaël ULg

Article for general public (2010)

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See detailA Best Practice Guide for Outreach to Schools
Heward, A.; Doran, R.; Nazé, Yaël ULg et al

(2010, September 01)

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See detailNew findings on the prototypical Of?p stars
Nazé, Yaël ULg; Ud-Doula, Asif; Spano, Maxime et al

in Astronomy and Astrophysics (2010), 520

<BR /> Aims: In recent years several in-depth investigations of the three prototypical Of?p stars were undertaken. These multiwavelength studies revealed the peculiar properties of these objects (in the X ... [more ▼]

<BR /> Aims: In recent years several in-depth investigations of the three prototypical Of?p stars were undertaken. These multiwavelength studies revealed the peculiar properties of these objects (in the X-rays as well as in the optical): magnetic fields, periodic line profile variations, recurrent photometric changes. However, many questions remain unsolved. <BR /> Methods: To clarify some of the properties of the Of?p stars, we have continued their monitoring. A new xmm-Newton observation and two new optical datasets were obtained. <BR /> Results: Additional information about the prototypical Of?p trio has been found. HD 108 has now reached its quiescent, minimum-emission state for the first time in 50-60 yr. The échelle spectra of HD 148937 confirm the presence of the 7d variations in the Balmer lines and reveal similar periodic variations (though of lower amplitudes) in the He i λ 5876 and He ii λ 4686 lines, underlining its similarities with the other two prototypical Of?p stars. The new xmm-Newton observation of HD 191612 was taken at the same phase in the line modulation cycle, but at a different orbital phase from previous data. It clearly shows that the X-ray emission of HD 191612 is modulated by the 538d period and not by the orbital period of 1542d - it is thus not of colliding-wind origin. The phenomenon responsible for the optical changes appears also at work in the high-energy domain. There are problems however: our MHD simulations of the wind magnetic confinement predict both a harder X-ray flux of a much larger strength than what is observed (the modelled differential emission measure peaks at 30-40 MK, whereas the observed one peaks at 2 MK) and narrow lines (hot gas moving with velocities of 100-200 km s[SUP]-1[/SUP], whereas the observed full width at half maximum is ~2000 km s[SUP]-1[/SUP]). Based on observations collected at the Haute-Provence Observatory, at the La Silla and San Pedro Mártir Observatories, and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]

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See detailFirst Orbital Solution for the Non-thermal Emitter Cyg OB2 No. 9
Nazé, Yaël ULg; Damerdji, Yassine ULg; Rauw, Grégor ULg et al

in Astrophysical Journal (2010), 719

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star ... [more ▼]

After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star. Since the discovery paper of 2008, a second periastron passage has occurred in 2009 February. Using a variety of techniques, the radial velocities could be estimated and a first, preliminary orbital solution was derived from the He I 5876 line. The mass ratio appears close to unity and the eccentricity is large, i.e., 0.7-0.75. X-ray data from 2004 and 2007 are also analyzed in quest of peculiarities linked to binarity. The observations reveal neither large overluminosity nor strong hardness, but it must be noted that the high-energy data were taken after the periastron passage, at a time where colliding wind emission may be low. Some unusual X-ray variability is however detected, with a 10% flux decrease between 2004 and 2007. To clarify their origin and find a more obvious signature of the wind-wind collision, additional data, taken at periastron and close to it, are needed. Based on observations collected at the Haute-Provence Observatory and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [less ▲]

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See detailMassive binaries as seen with GAIA
Palate, Matthieu ULg; Rauw, Grégor ULg; Gosset, Eric ULg et al

Poster (2010, July)

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See detailThe quest for the most massive star
Nazé, Yaël ULg

Article for general public (2010)

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See detailVénus version Express
Nazé, Yaël ULg

Article for general public (2010)

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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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