References of "Gosset, Eric"
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See detailCorrection of Systematic Errors in Differential Photometry
Manfroid, Jean ULg; Royer, P.; Rauw, Grégor ULg et al

in Astronomical Data Analysis Software and Systems X (2001)

A common cause of errors in CCD differential photometry is an improper calibration of the array. The importance of these errors is evaluated for different cameras with fields between 3 and 30 arcminutes ... [more ▼]

A common cause of errors in CCD differential photometry is an improper calibration of the array. The importance of these errors is evaluated for different cameras with fields between 3 and 30 arcminutes. The usual superflat illumination corrections based on night sky exposures are often found to be unsatisfactory. ``Photometric superflats'' based on stellar measurements are more reliable and should be used instead. [less ▲]

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See detailSimulations of observations with the Optical Monitor of the X-ray Multi-Mirror Satellite
Royer, P.; Manfroid, Jean ULg; Gosset, Eric ULg et al

in Astronomy and Astrophysics. Supplement Series (2000), 145

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric ... [more ▼]

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric system and its colour transformations towards the standard U BV system. Second, we establish a set of procedures to determine the temperature and the amount of interstellar absorption affecting the observed stars. Last, we address the possibility of isolating quasars in multidimensional colour diagrams based on the XMM-OM filter set. [less ▲]

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See detailA new orbital solution for the massive binary system HD 93403
Rauw, Grégor ULg; Sana, H.; Gosset, Eric ULg et al

in Astronomy and Astrophysics (2000), 360

We present a spectroscopic analysis of the early-type massive binary system HD 93403. Using high resolution optical spectra, we clearly separate the primary and secondary components. For the first time ... [more ▼]

We present a spectroscopic analysis of the early-type massive binary system HD 93403. Using high resolution optical spectra, we clearly separate the primary and secondary components. For the first time, we are able to provide an orbital solution for both stars. Our new orbital parameters show discrepancies with the previous solution published by Thackeray & Emerson (?). We further discuss several spectral features of HD 93403. We finally derive qualitative constraints on the inclination of the system and we discuss its evolutionary status and the position of both components in the Hertzsprung-Russell diagram. Based on observations collected at the European Southern Observatory (La Silla, Chile) and the Cerro Tololo Inter-American Observatory (CTIO). [less ▲]

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See detailOn the perspectives of using XMM to study fundamental parameters of early-type stars
Rauw, Grégor ULg; van der Hucht, K. A.; Mewe, R. et al

in Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies (1999)

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See detailNew observational results on the colliding wind WR+O binary WR 30a
Gosset, Eric ULg; Royer, P.; Rauw, Grégor ULg et al

in Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies (1999)

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See detailNarrow-band photometry of the eclipsing WN7+O binary WR 22
Royer, P.; Rauw, Grégor ULg; Manfroid, Jean ULg et al

in Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies (1999)

In the present paper, we discuss photometric observations of the February 1996 eclipse of the very massive WR+O binary WR 22. Our data were obtained with a set of narrow-band filters, specially designed ... [more ▼]

In the present paper, we discuss photometric observations of the February 1996 eclipse of the very massive WR+O binary WR 22. Our data were obtained with a set of narrow-band filters, specially designed for the study of WR stars. [less ▲]

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See detailX-Ray Spectroscopy with XMM: A New Powerful Tool to Determine Fundamental Parameters of Early-type Stars
Mewe, R.; Rauw, Grégor ULg; van der Hucht, K. A. et al

(1998)

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See detailESO & NOT photometric monitoring of the Cloverleaf quasar
Ostensen, R.; Remy, M.; Lindblad, P. O. et al

in Astronomy and Astrophysics. Supplement Series (1997), 126

The Cloverleaf quasar, H1413+117, has been photometrically monitored at ESO (La Silla, Chile) and with the NOT (La Palma, Spain) during the period 1987--1994. All good quality CCD frames have been ... [more ▼]

The Cloverleaf quasar, H1413+117, has been photometrically monitored at ESO (La Silla, Chile) and with the NOT (La Palma, Spain) during the period 1987--1994. All good quality CCD frames have been successfully analysed using two independent methods (i.e. an automatic image decomposition technique and an interactive CLEAN algorithm). The photometric results from the two methods are found to be very similar, and they show that the four lensed QSO images vary significantly in brightness (by up to 0.45 mag), nearly in parallel. The lightcurve of the $D$ component presents some slight departures from the general trend which are very likely caused by micro-lensing effects. Upper limits, at the 99% confidence level, of 150 days on the absolute value for the time delays between the photometric lightcurves of this quadruply imaged variable QSO, are derived. This is unfortunately too large to constrain the lens model but there is little doubt that a better sampling of the lightcurves should allow to accurately derive these time delays. Pending a direct detection of the lensing galaxy (position and redshift), this system thus constitutes another good candidate for a direct and independent determination of the Hubble parameter. Based on observations collected at the European Southern Observatory (La Silla, Chile) and with the Nordic Optical Telescope (La Palma, Spain). Table 1. Logbook for the ESO and NOT observations together with photometric results for the Cloverleaf quasar. This long table can be accessed on the WWW at the URL address: http://vela.astro.ulg.ac.be/grav_lens/glp_homepage.html} [less ▲]

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See detailLa restauration de la Grande Lunette Méridienne de l'Observatoire de Cointe.
Gosset, Eric ULg

in Ciel (Le) (1997), 59

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See detailSurveys of ultraviolet-excess quasar candidates in large fields
Gosset, Eric ULg; Moreau, O.; Surdej, Jean ULg et al

in Astronomy and Astrophysics. Supplement Series (1997), 123

We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet ... [more ▼]

We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates were selected on the basis of their $U$ image being too bright. The spectroscopic identification of the primary candidates led to the discovery of 59 bona fide quasars (out of which 6 were previously known). The Palomar Schmidt plate was digitised using the MAMA measuring machine and the outcoming data reduced using ad hoc procedures. A photometric calibration allowed us to derive values for the limiting magnitudes and for the U-B index selection threshold of the survey. A catalogue containing 60 quasars is presented with accurate positions, magnitudes and additional information such as redshifts. We studied the spatial distribution of the objects and detected, for the quasars of our sample, a significant deviation from randomness in the form of a propensity to cluster in pairs on the celestial sphere with a typical scale of about 10 arcmin. We also formally detected a tendency towards a 3-D clustering, but this result is induced by a single pair of quasars. A forthcoming paper will deal with a similar work performed in a field around NGC 520; the latter field is located directly to the North of the present one and slightly overlaps it. Based on observations acquired at the Mount Palomar and Las Campanas Observatories as well as at the European Southern Observatory. Also based on Schmidt-plate digitisations performed with the MAMA measuring machine of C.A.I. (I.N.S.U., Paris). [less ▲]

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See detailSearch for Interacting Winds in the WN7 + O Binary WR 22
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Gosset, Eric ULg

in Revista Mexicana de Astronomia y Astrofisica Conference Series (1996, December 01)

We present new spectroscopic observations of the He I Lambda5876 line in WR22 which were obtained around periastron. These data show strong line profile variability. We use recently determined orbital ... [more ▼]

We present new spectroscopic observations of the He I Lambda5876 line in WR22 which were obtained around periastron. These data show strong line profile variability. We use recently determined orbital elements of WR22 to discuss the possibility of tidal interactions or of a colliding wind phenomenon affecting the outer parts of the Wolf-Rayet atmosphere. [less ▲]

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See detailExistence of a short period (3.5-4 hours) in the photometric variability of WR 66.
Rauw, Grégor ULg; Gosset, Eric ULg; Manfroid, Jean ULg et al

in Astronomy and Astrophysics (1996), 306

We report here on an independent detection of a short period (~4hours) in the photometric variations of WR66, thus confirming in broad terms the discovery by Antokhin et al.. In addition, we present the ... [more ▼]

We report here on an independent detection of a short period (~4hours) in the photometric variations of WR66, thus confirming in broad terms the discovery by Antokhin et al.. In addition, we present the first spectroscopic variability analysis for this star. A few peculiarities of the spectrum of WR66 are also discussed. Finally, we perform a brief examination of different possible origins of the phenomenon. [less ▲]

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See detailWR22: the most massive Wolf-Rayet star ever weighed.
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Gosset, Eric ULg et al

in Astronomy and Astrophysics (1996), 306

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the ... [more ▼]

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the orbit, formerly determined on the basis of photographic spectra. The high signal-to-noise ratio of our data also allows the detection of some weak absorption lines which, for the first time, can definitely be attributed to the companion. A study of their radial velocities gives a mass ratio of m_WR_/m_O_=2.78 leading to a minimum mass of 72M[SUB]sun[/SUB]_ for the WN7 star. The companion can be classified as a "late O" (O6.5-O8.5) star with a luminosity ratio of the system q=L_WR_^y^/L_O_^y^ at 5500A of about 8. The exceptionally high mass of the WN7 star and its high hydrogen mass-fraction suggest that WR22 is at the beginning of its Wolf-Rayet evolution. As a matter of fact, with such a high mass, WR22 most probably is still a hydrogen burning object. Therefore, the WN7 component is much closer to a main sequence O star with a "Wolf-Rayet clothing" than to the other members of the Wolf-Rayet family, which are rather highly evolved He-burning descendants of massive progenitors. [less ▲]

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See detailWolf-Rayet stars in the framework of stellar evolution.
Vreux, Jean-Marie ULg; Detal, Alain ULg; Fraipont-Caro, D. et al

Book (1996)

The following topics were dealt with: evolution of massive stars - theory; observational characteristics of Wolf-Rayet stars and related objects; evidences for evolutionary links - transition objects ... [more ▼]

The following topics were dealt with: evolution of massive stars - theory; observational characteristics of Wolf-Rayet stars and related objects; evidences for evolutionary links - transition objects; analysis of the observations - the models and their results; massive stars in starburst. [less ▲]

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See detailWR 134 line-profile variability : preliminary results of the 1994 campaign
Gosset, Eric ULg; Vreux, Jean-Marie ULg

in Vreux, J.-M.; Detal, Alain; Fraipont-Caro, Denise (Eds.) et al Wolf-Rayet stars in the framework of stellar evolution (1996)

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See detailThe Clover Leaf Quasar H1413+117: New Photometric Light Curves
Remy, M.; Gosset, Eric ULg; Hutsemekers, Damien ULg et al

in Kochanek, C. S.; Hewitt, Jacqueline N (Eds.) Astrophysical applications of gravitational lensing: proceedings of the 173rd Symposium of the International Astronomical Union (1996)

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See detailA new orbital solution for the WNL binary system WR12
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Gosset, Eric ULg et al

in Liege International Astrophysical Colloquia (1996)

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See detailA Deep Multicolour CCD Survey for Quasar Candidates with the OCA Schmidt Telescope
Moreau, O.; Gosset, Eric ULg; Royer, P. et al

in ASP Conf. Series (1995), 84

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See detailWR22 as a core hydrogen-burning Wolf-Rayet star
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Gosset, Eric ULg et al

in Stellar evolution: what should be done; 32nd Liege International Astrophysical Coll. (1995)

The analysis of an extensive sample of high resolution spectra of the Wolf-Rayet binary WR22 recently allowed us to determine a minimum mass of 72 M_solar for the WN7 star. With such a high mass, WR22 is ... [more ▼]

The analysis of an extensive sample of high resolution spectra of the Wolf-Rayet binary WR22 recently allowed us to determine a minimum mass of 72 M_solar for the WN7 star. With such a high mass, WR22 is expected to be a core H-Burning star which has just evolved from a progenitor of at least 90-110 M_solar. [less ▲]

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