Publications of Jean-Marie Vreux
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See detailHD 108: The mystery deepens with XMM-Newton observations
Nazé, Yaël ULiege; Rauw, Grégor ULiege; Vreux, Jean-Marie ULiege et al

in Astronomy and Astrophysics (2004), 417(2), 667-677

In 2001, using a large spectroscopic dataset from an extensive monitoring campaign, we discovered that the peculiar Of star HD 108 displayed extreme line variations. This strange behaviour could be ... [more ▼]

In 2001, using a large spectroscopic dataset from an extensive monitoring campaign, we discovered that the peculiar Of star HD 108 displayed extreme line variations. This strange behaviour could be attributed to a variety of models, and an investigation of the high energy properties of HD 108 was needed to test the predictions from these models. Our dedicated XMM-Newton observation of HD 108 shows that its spectrum is well represented by a two temperature thermal plasma model with kT(1) similar to 0.2 keV and kT(2) similar to 1.4 keV. In addition, we find that the star does not display any significant short-term changes during the XMM-Newton exposure. Compared to previous Einstein and ROSAT detections, it also appears that HD 108 does not present long-term flux variations either. While the line variations continue to modify HD 108's spectrum in the optical domain, the X-ray emission of the star appears thus surprisingly stable: no simple model is for the moment able to explain such an unexpected behaviour. Thanks to its high sensitivity, the XMM-Newton observatory has also enabled the serendipitous discovery of 57 new X-ray sources in the field of HD 108. Their properties are also discussed in this paper. [less ▲]

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See detailWR bubbles and HeII emission
Nazé, Yaël ULiege; Rauw, Grégor ULiege; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2003), 408(1), 171-186

We present the very first high quality images of the He II lambda4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99 ... [more ▼]

We present the very first high quality images of the He II lambda4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99-2, was analysed in a previous letter. Using VLT FORS data, we investigate the morphology of the ring nebulae around the early-type WN stars BAT99-49 [less ▲]

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See detailXMM-Newton high-resolution X-ray spectroscopy of the Wolf-Rayet object WR 25 in the Carina OB1 association
Raassen, A. J. J.; van der Hucht, K. A.; Mewe, R. et al

in Astronomy and Astrophysics (2003), 402(2), 653-666

We report the analysis of the first high-resolution X-ray spectra of the Wolf-Rayet (WR) object WR25 (HD 93162, WN6ha+O4f) obtained with the reflection Grating spectrometers (RGS) and the European photon ... [more ▼]

We report the analysis of the first high-resolution X-ray spectra of the Wolf-Rayet (WR) object WR25 (HD 93162, WN6ha+O4f) obtained with the reflection Grating spectrometers (RGS) and the European photon imaging cameras (EPIC-MOS and PN) CCD spectrometers on board the XMM-Newton satellite. The spectrum exhibits bright emission lines of the H- and He-like ions of Ne, Mg, Si and S, as well as Fe XVIII to Fe XX and Fe XXV lines. Line fluxes have been measured. The RGS and e pi c spectra have been simultaneously fitted to obtain self-consistent temperatures, emission measures, and elemental abundances. Strong absorption by the dense WR stellar wind and the interstellar medium (ISM) is observed equivalent to N-H = 7x10(21) cm(-2). Multi-temperature (DEM) fitting yields two dominant components around temperatures of 7.0 and 32 MK, respectively. The XMM intrinsic (i.e. unabsorbed, corrected for the stellar wind absorption and the absorption of ISM) X-ray luminosity of WR25 is L-x(0.5-10 keV) = 1.3x10(34) erg s(-1), and L-x(0.5-10 keV) = 0.85 x 10(34) erg s(-1), (when correcting for the ISM only) assuming d = 3.24 kpc. The obtained chemical abundances are subsolar, except for S. This may be real, but could equally well be due to a weak coupling to the continuum, which is strongly influenced by the absorption column density and the subtracted background. The expected high N-abundance, as observed in the optical wavelength region, could not be confirmed due to the strong wind absorption, blocking out its spectral signature. The presence of the Fe XXV emission-line complex at similar to6.7 keV is argued as being indicative for colliding winds inside a WR+O binary system. [less ▲]

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See detailVLT observations of the highly ionized nebula around Brey2
Nazé, Yaël ULiege; Rauw, Grégor ULiege; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2003), 401(2), 13-16

We present the first high resolution He II lambda4686 images of the high excitation nebula around the WR star Brey2 in the LMC. This nebula presents a striking morphology: a small arc-like feature some 3 ... [more ▼]

We present the first high resolution He II lambda4686 images of the high excitation nebula around the WR star Brey2 in the LMC. This nebula presents a striking morphology: a small arc-like feature some 3.6 pc in radius is particularly prominent in the He II lambda4686 line. We further discover a previously unknown faint He II emission that extends over an area of 22 x 17 pc(2). An even fainter He II emission is apparently associated with the interstellar bubble blown by the progenitor of Brey2. The total He II flux corresponds to an ionizing flux of 4 x 10(47) photons s(-1). Halpha, [O III], and He I lambda5876 images and long-slit spectra are also examined in this letter, enabling us to investigate the detailed physical properties at various locations of the nebula. [less ▲]

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See detailLine profile variability in the spectra of Oef stars. I. BD + 60deg 2522
Rauw, Grégor ULiege; De Becker, Michaël ULiege; Vreux, Jean-Marie ULiege

in Astronomy and Astrophysics (2003), 399

We report the analysis of a long term observing campaign designed to monitor the spectroscopic variability of the Oef star BD +60deg 2522. We find that the double-peaked He {II} lambda 4686 emission line ... [more ▼]

We report the analysis of a long term observing campaign designed to monitor the spectroscopic variability of the Oef star BD +60deg 2522. We find that the double-peaked He {II} lambda 4686 emission line undergoes strong profile variability on time scales of 2-3 day. However, the time scale as well as the pattern of these variations turn out to be epoch dependent and the phenomenon is thus most likely not ruled by a single stable clock. On the other hand, the absorption lines in the spectrum of BD +60deg 2522 display line profile variability on time scales of a few hours that might be related to non-radial pulsations. We tentatively propose that the beating of several non-radial pulsation modes triggers transient large-scale density perturbations in a confined stellar wind that produce the 2-3 day time scale variability. [less ▲]

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See detailPreliminary results from XMM-Newton observations of the massive Wolf-Rayet binary WR 22 (WN7h+O9III-V)
Gosset, Eric ULiege; Rauw, Grégor ULiege; Vreux, Jean-Marie ULiege et al

in A Massive Star Odyssey: From Main Sequence to Supernova (2003)

We present preliminary results from observations of the massive WR+O binary WR 22 performed with the XMM observatory. The star is brighter in the X-ray domain near apastron and fainter at periastron. The ... [more ▼]

We present preliminary results from observations of the massive WR+O binary WR 22 performed with the XMM observatory. The star is brighter in the X-ray domain near apastron and fainter at periastron. The change in brightness is very progressive and mainly corresponds to a lowering of the soft part of the spectrum. [less ▲]

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See detailSearch for X-ray Variability in Early-type Stars in the Carina OB1 Association with XMM-Newton
Antokhin, I. I.; Rauw, Grégor ULiege; Vreux, Jean-Marie ULiege et al

in Astronomical Society of the Pacific Conference Series (2003)

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See detailXMM-Newton high-resolution X-ray spectroscopy of the Wolf-Rayet object WR25 (WN6ha+O4f)
Raassen, A. J. J.; van der Hucht, K. A.; Mewe, R. et al

in Advances in Space Research (2003), 32(6), 1161-1165

We report the analysis of the X-ray spectrum of the Wolf-Rayet star WR 25, observed by RGS and EPIC-MOS on board XMM-Newton. Temperatures up to 40 MK have been determined. Strong absorption, exceeding the ... [more ▼]

We report the analysis of the X-ray spectrum of the Wolf-Rayet star WR 25, observed by RGS and EPIC-MOS on board XMM-Newton. Temperatures up to 40 MK have been determined. Strong absorption, exceeding the value due to the Inter Stellar Medium (ISM) has been detected and assigned to the dense stellar wind. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe evolved early-type binary HDE 228766 revisited
Rauw, Grégor ULiege; Crowther, P. A.; Eenens, P. R. J. et al

in Astronomy and Astrophysics (2002), 392(2), 563-574

We use an extensive set of spectroscopic observations to reinvestigate the properties of the massive binary HDE 228766. Conventional classification criteria suggest that HDE 228766 consists of an O7 ... [more ▼]

We use an extensive set of spectroscopic observations to reinvestigate the properties of the massive binary HDE 228766. Conventional classification criteria suggest that HDE 228766 consists of an O7 primary and an Of(+) secondary. However, several spectral features of the secondary, such as the simultaneous presence of N III, N IV and N V emissions, make it a rather unusual object. We find that the orbital motion of the secondary is probably best described by the radial velocities of the narrow N III emission lines. Our orbital solution yields m(1) sin(3) i = 31:7 and m(2) sin(3) i = 25:5 M. for the primary and secondary respectively. The He II lambda 4542 absorption in the secondary's spectrum appears considerably blue-shifted with respect to the narrow emission lines, indicating that the absorption is probably formed in the accelerating part of the secondary's wind. We use a tomographic technique to investigate the profile variability of the broader emission lines. In addition to a strong emission from the secondary, the Halpha line displays a weak emission feature that is probably associated with a wind interaction region located near the surface of the primary star. Finally, our analysis of the spectrum with a non-LTE code indicates that the secondary is an evolved object that exhibits some CNO processed material in its atmosphere and has a large mass loss rate. Assuming a distance of 3.5 kpc (which follows from adopting M-V,M-s = -6 for the secondary) we infer (M) over dot similar or equal to 10(5) M. yr(-1) for the secondary. Our results suggest that HDE 228766 could be in a post-Roche lobe overflow stage. The secondary may be classified as WN8ha and is currently in a transition stage between a "normal" Of staranda WNL-type Wolf-Rayet star. [less ▲]

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See detailPhase-resolved X-ray and optical spectroscopy of the massive binary HD 93403
Rauw, Grégor ULiege; Vreux, Jean-Marie ULiege; Stevens, I. R. et al

in Astronomy and Astrophysics (2002), 388(2), 552-562

We report the first results of a campaign aimed at the study of early-type binaries with the XMM-Newton observatory. Phase-resolved EPIC spectroscopy of the eccentric binary HD93403 reveals a clear ... [more ▼]

We report the first results of a campaign aimed at the study of early-type binaries with the XMM-Newton observatory. Phase-resolved EPIC spectroscopy of the eccentric binary HD93403 reveals a clear orbital modulation of the X-ray luminosity as a function of the orbital phase. Below 1.0 keV, the observed X-ray flux is modulated by the opacity of the primary wind. Above 1.0 keV, the observed variation of the X-ray flux is roughly consistent with a 1/r dependence expected for an adiabatic colliding wind interaction. HD93403 appears less overluminuous in X-rays than previously thought and a significant fraction of the total X-ray emission arises probably within the winds of the individual components of the binary. Optical monitoring of the system reveals strong variability of the He II lambda 4686 and Halpha line profiles. The He II lambda 4686 line displays a broad asymmetrical emission component which is found to be significantly stronger between phases 0.80 and 0.15 than around apastron. This suggests that part of the emission arises in the interaction region and most probably in the trailing arm of a shock cone wrapped around the secondary. Some absorption lines of the secondary's spectrum display equivalent width variations reminiscent of the so-called Struve-Sahade effect. The differences in behaviour between individual lines suggest that the temperature may not be the only relevant parameter that controls this effect. [less ▲]

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See detailOptical Spectroscopy of Colliding-Wind Systems to be Observed with XMM
Sana, H.; Rauw, Grégor ULiege; Gosset, Eric ULiege et al

in Interacting Winds from Massive Stars (2002)

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See detailSearching for Colliding-Wind Signatures in a Sample of O-Star Binaries
Rauw, Grégor ULiege; Sana, H.; Vreux, Jean-Marie ULiege et al

in Interacting Winds from Massive Stars (2002)

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See detailA first detailed study of the colliding wind WR+O binary WR 30a
Gosset, Eric ULiege; Royer, P.; Rauw, Grégor ULiege et al

in Monthly Notices of the Royal Astronomical Society (2001), 327

We present a detailed, extensive investigation of the photometric and spectroscopic behaviour of WR 30a. This star is definitely a binary system with a period around 4.6d. We propose the value P=4.619d ... [more ▼]

We present a detailed, extensive investigation of the photometric and spectroscopic behaviour of WR 30a. This star is definitely a binary system with a period around 4.6d. We propose the value P=4.619d (sigma=0.002d). The identification of the components as WO4+O5((f)) indicates a massive evolved binary system; the O5 component is a main-sequence or, more likely, a giant star. The radial velocities of the O star yield a circular orbit with an amplitude K[SUB]O[/SUB]=29.9 (sigma=2.1)kms[SUP]-1[/SUP] and a mass function of 0.013 (sigma=0.003)M[SUB]solar[/SUB]. The spectrum of WR 30a exhibits strong profile variations of the broad emission lines that are phase-locked with the orbital period. We report the detection of the orbital motion of the WO component with K[SUB]WO[/SUB]=189kms[SUP]-1[/SUP], but this should be confirmed by further observations. If correct, it implies a mass ratio M[SUB]WO[/SUB] /M[SUB]O[/SUB]=0.16. The star exhibits sinusoidal light variations of amplitude 0.024mag peak-to-peak with the minimum of light occurring slightly after the conjunction with the O star in front. On the basis of the phase-locked profile variations of the Civ lambda4658 blend in the spectrum of the WO, we conclude that a wind-wind collision phenomenon is present in the system. We discuss some possibilities for the geometry of the interaction region. [less ▲]

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See detailOptical spectroscopy of XMEGA targets in the Carina Nebula - III. The multiple system Tr 16-104 (â ¡CPD -59° 2603)
Rauw, Grégor ULiege; Sana, H.; Antokhin, I. I. et al

in Monthly Notices of the Royal Astronomical Society (2001), 326

We discuss the orbital elements of the multiple system Tr 16-104 which is usually believed to be a member of the open cluster Trumpler 16 in the Carina complex. We show that Tr 16-104 could be a ... [more ▼]

We discuss the orbital elements of the multiple system Tr 16-104 which is usually believed to be a member of the open cluster Trumpler 16 in the Carina complex. We show that Tr 16-104 could be a hierarchical triple system consisting of a short-period (2.15d) eclipsing O7V+O9.5V binary bound to a B0.2 IV star. Our preliminary orbital solution of the third body indicates that the B star most probably describes an eccentric orbit with a period of ~285 or ~1341d around the close binary. Folding photometric data from the literature with our new ephemerides, we find that the light curve of the close binary exhibits rather narrow eclipses indicating that the two O stars must be well inside their Roche lobes. Our analysis of the photometric data yields a lower limit on the inclination of the orbit of the close binary of i>=77°. The stellar radii and luminosities of the O7 V and O9.5 V stars are significantly smaller than expected for stars of this spectral type. Our results suggest that Tr 16-104 lies at a distance of the order of 2.5kpc and support a fainter absolute magnitude for zero-age main-sequence O stars than usually adopted. We find that the dynamical configuration of Tr 16-104 corresponds to a hierarchical system that should remain stable provided that it suffers no strong perturbation. Finally, we also report long-term temporal variations of high-velocity interstellar Caii absorptions in the line of sight towards Tr 16-104. [less ▲]

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See detailWhat is the real nature of HD 108?
Nazé, Yaël ULiege; Vreux, Jean-Marie ULiege; Rauw, Grégor ULiege

in Astronomy and Astrophysics (2001), 372

Since the beginning of the past century, the nature of HD 108 has been a subject of intense debate. One after another, astronomers explored its variability and attributed it either to binarity, or to ... [more ▼]

Since the beginning of the past century, the nature of HD 108 has been a subject of intense debate. One after another, astronomers explored its variability and attributed it either to binarity, or to changes in the stellar wind of a single star. In this article, we analyse a 30 year campaign of spectroscopic observations of this star with special emphasis on the last 15 years during which photographic plates have been replaced by CCD detectors. Our investigation of the radial velocities of HD 108 yields no significant short- or long-term period and does not confirm the published periodicities either. Though the radial velocity of HD 108 appears clearly variable, the variations cannot be explained by the orbital motion in a spectroscopic binary. However, our data reveal spectacular changes in the H I Balmer lines and some He I profiles over the years. These lines continuously evolved from P Cygni profiles to ``pure'' absorption lines. A similar behaviour has already been observed in the past, suggesting that these changes are recurrent. HD 108 seems to share several characteristics of Oe stars and we discuss different hypotheses for the origin of the observed long-term variations. As we are now in a transition period, a continuous monitoring of HD 108 should be considered for the next few years. Based on observations collected at the Observatoire de Haute-Provence (France). [less ▲]

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See detailThe strange case of the massive binary HD 149404
Rauw, Grégor ULiege; Nazé, Yaël ULiege; Carrier, F. et al

in Astronomy and Astrophysics (2001), 368

We report the analysis of an extensive set of high-resolution spectroscopic observations of the massive binary system HD 149404. We compare different techniques to measure the radial velocities of the ... [more ▼]

We report the analysis of an extensive set of high-resolution spectroscopic observations of the massive binary system HD 149404. We compare different techniques to measure the radial velocities of the heavily blended absorption lines and we derive a new orbital solution. The absorption lines display strong variability that slightly affects the orbital solution and the determination of the spectral types of the components of the binary. We find that the primary is probably of spectral type O7.5 I(f), while the secondary is most likely an ON9.7 I supergiant. The secondary seems to be the most evolved component of the system and its current evolutionary status could best be explained if the system has undergone a Roche lobe overflow episode during the past. The secondary could actually still be rather close to filling its critical volume and this could lead to an enhanced mass loss of the secondary. The spectrum of HD 149404 displays many emission lines some of which show phase-locked line profile variations. In particular, the Halpha line displays a double-peaked morphology at orbital phases near conjunction. We investigate the radial velocity behaviour of the emission lines and we find that some of them must be formed in an interaction region. We propose a simple model where some of the optical emission lines arise in a heavily bended shock region. Based on observations collected at the European Southern Observatory (La Silla, Chile) and at the Cerro Tololo Inter-American Observatory (CTIO). [less ▲]

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See detailThe WR content of IC10 - first detection of WC9 stars in a low metallicity environment?
Royer, P.; Smartt, S. J.; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2001), 366

We present deep, narrow-band photometry of the Local Group starburst galaxy IC 10. Our dedicated photometric system provides detection of 13 new Wolf-Rayet (WR) stars and allows spectral subtypes to be ... [more ▼]

We present deep, narrow-band photometry of the Local Group starburst galaxy IC 10. Our dedicated photometric system provides detection of 13 new Wolf-Rayet (WR) stars and allows spectral subtypes to be assigned. Three of these new stars appear to be WC9 subtypes. If confirmed, these would be the very first WC9 stars ever detected in a low metallicity environment, hence putting strong new constraints on the formation and evolution models of massive stars. Eight of the new WR stars are of the WC subtype, which does not significantly modify the anomalously high WC/WN ratio in IC 10. However it is likely that a number of Wolf-Rayet stars of the WNE and WC spectral subtypes are still to be discovered in the heart of the galaxy. Based on observations at the William Herschel Telescope on La Palma and at the Observatoire de Haute-Provence. [less ▲]

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See detailThe spectral variability of HD 192639 and its implications for the star's wind structure
Rauw, Grégor ULiege; Morrison, N. D.; Vreux, Jean-Marie ULiege et al

in Astronomy and Astrophysics (2001), 366

We report the analysis of an extensive set of spectroscopic data of the O(f) supergiant HD 192639. A Fourier analysis of our time-series reveals a recurrent variability with a ``period'' of roughly 4.8 ... [more ▼]

We report the analysis of an extensive set of spectroscopic data of the O(f) supergiant HD 192639. A Fourier analysis of our time-series reveals a recurrent variability with a ``period'' of roughly 4.8 days which is most prominent in the absorption components of the He {ii}\ lambda 4686 and Halpha P-Cygni profiles. The same periodicity is also detected in the blue wing of several absorption lines (e.g. Hbeta ). The variations of the absorption components correspond most probably to a cyclical modulation of the amount of stellar wind material along the line of sight towards the star. The 4.8-day period affects also the morphology of the double-peaked He {ii}\ lambda 4686 and Halpha emission components, although these emission components display also variations on other (mainly longer) time scales. The most likely explanation for the 4.8-day modulation is that this cycle reflects the stellar rotational period (or half this period). We find that the most important observational properties can be explained - at least qualitatively - by a corotating interaction region or a tilted confined corotating wind. Based on observations collected at the Observatoire de Haute Provence, France and the Ritter Observatory, Toledo, USA. [less ▲]

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See detailHigh resolution X-ray spectroscopy of zeta Puppis with the XMM-Newton reflection grating spectrometer
Kahn, S. M.; Leutenegger, M. A.; Cottam, J. et al

in Astronomy and Astrophysics (2001), 365

We present the first high resolution X-ray spectrum of the bright O4Ief supergiant star zeta Puppis, obtained with the Reflection Grating Spectrometer on-board XMM-Newton. The spectrum exhibits bright ... [more ▼]

We present the first high resolution X-ray spectrum of the bright O4Ief supergiant star zeta Puppis, obtained with the Reflection Grating Spectrometer on-board XMM-Newton. The spectrum exhibits bright emission lines of hydrogen-like and helium-like ions of nitrogen, oxygen, neon, magnesium, and silicon, as well as neon-like ions of iron. The lines are all significantly resolved, with characteristic velocity widths of order 1000-1500 km s[SUP]-1[/SUP]. The nitrogen lines are especially strong, and indicate that the shocked gas in the wind is mixed with CNO-burned material, as has been previously inferred for the atmosphere of this star from ultraviolet spectra. We find that the forbidden to intercombination line ratios within the helium-like triplets are anomalously low for N VI, O VII, and Ne IX. While this is sometimes indicative of high electron density, we show that in this case, it is instead caused by the intense ultraviolet radiation field of the star. We use this interpretation to derive constraints on the location of the X-ray emitting shocks within the wind that are consistent with current theoretical models for this system. [less ▲]

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See detailAn XMM-Newton Study of 9SGR and the Lagoon Nebula
Rauw, Grégor ULiege; Blomme, R.; Waldron, W. L. et al

Conference (2001, January 01)

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