Publications ORBi OA
Bookmark and Share    
Full Text
Peer Reviewed
See detailCircumstellar material in the Vega inner system revealed by CHARA/FLUOR
Absil, Olivier ULg; di Folco, E.; Mérand, A. et al

in Astronomy and Astrophysics (2006), 452

Context: Only a handful of debris disks have been imaged up to now. Due to the need for high dynamic range and high angular resolution, very little is known about the inner planetary region, where small ... [more ▼]

Context: Only a handful of debris disks have been imaged up to now. Due to the need for high dynamic range and high angular resolution, very little is known about the inner planetary region, where small amounts of warm dust are expected to be found. Aims: We investigate the close neighbourhood of Vega with the help of infrared stellar interferometry and estimate the integrated K-band flux originating from the central 8 AU of the debris disk. Methods: We performed precise visibility measurements at both short (~30 m) and long (~150 m) baselines with the FLUOR beam-combiner installed at the CHARA Array (Mt Wilson, California) in order to separately resolve the emissions from the extended debris disk (short baselines) and from the stellar photosphere (long baselines). Results: After revising Vega's K-band angular diameter (theta_UD = 3.202 ± 0.005 mas), we show that a significant deficit in squared visibility (Delta V[SUP]2[/SUP] = 1.88 ± 0.34%) is detected at short baselines with respect to the best-fit uniform disk stellar model. This deficit can be either attributed to the presence of a low-mass stellar companion around Vega, or as the signature of the thermal and scattered emissions from the debris disk. We show that the presence of a close companion is highly unlikely, as well as other possible perturbations (stellar morphology, calibration), and deduce that we have most probably detected the presence of dust in the close neighbourhood of Vega. The resulting flux ratio between the stellar photosphere and the debris disk amounts to 1.29 ± 0.19% within the FLUOR field-of-view (~7.8 AU). Finally, we complement our K-band study with archival photometric and interferometric data in order to evaluate the main physical properties of the inner dust disk. The inferred properties suggest that the Vega system could be currently undergoing major dynamical perturbations. [less ▲]

Detailed reference viewed: 31 (7 ULg)
Full Text
See detailL'astronomie dans le monde
Manfroid, Jean ULg

Article for general public (2006)

Deep Impact; Comète 73P/Schwassmann-Wachmann 3; L'anneau bleu d'Uranus; Triplet de neptunes; Triton; Dunes de Titan; Aréologie; Tache Rouge Junior; Obliquité des grosses planètes; Le jour de Saturne; Xéna ... [more ▼]

Deep Impact; Comète 73P/Schwassmann-Wachmann 3; L'anneau bleu d'Uranus; Triplet de neptunes; Triton; Dunes de Titan; Aréologie; Tache Rouge Junior; Obliquité des grosses planètes; Le jour de Saturne; Xéna; Un compagnon pour le Soleil; Galaxies satellites; Séisme sur une étoile à  neutrons; Trou noir double; Hydrogène lointain [less ▲]

Detailed reference viewed: 2 (0 ULg)
Full Text
Peer Reviewed
See detailA View to the Future: Ultraviolet Studies of the Solar System
Brosch, Noah; Davies, John; Festou, Michel C et al

in Astrophysics & Space Science (2006), 303

We discuss the status of ultraviolet knowledge of Solar System objects. We begin with a short historical survey, followed by a review of knowledge gathered so far and of existing observational assets. The ... [more ▼]

We discuss the status of ultraviolet knowledge of Solar System objects. We begin with a short historical survey, followed by a review of knowledge gathered so far and of existing observational assets. The survey indicates that UV observations, along with data collected in other spectral bands, are necessary and in some cases essential to understand the nature of our neighbors in the Solar System. By extension, similar observations are needed to explore the nature of extrasolar planets, to support or reject astro-biology arguments, and to compose and test scenarios for the formation and evolution of planetary systems. We propose a set of observations, describing first the necessary instrumental capabilitites to collect these and outlining what would be the expected scientific return. We identify two immediate programmatic requirements: the establishment of a mineralogic database in the ultraviolet for the characterization of planetary, ring, satellite, and minor planet surfaces, and the development and deployment of small orbital solar radiation monitors. The first would extend the methods of characterizing surfaces of atmosphere-less bodies by adding the UV segment. The latter are needed to establish a baseline against which contemporaneous UV observations of Solar System objects must be compared. We identify two types of UV missions, one appropriate for a two-meter-class telescope using almost off-the-shelf technology that could be launched in the next few years, and another for a much larger (5--20 meter class) instrument that would provide the logical follow-up after a decade of utilizing the smaller facility. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
See detailThe Host Galaxies of the Brightest Quasars: Gas-Rich Galaxies, Mergers, and Young Stars
Courbin, Frédéric; Letawe, Géraldine ULg; Meylan, Georges et al

in The Messenger (2006), 124

Because they are faint and hidden in the glare of a much brighter unresolved source, quasar host galaxies still challenge the most powerful telescopes, instrumentation and processing techniques ... [more ▼]

Because they are faint and hidden in the glare of a much brighter unresolved source, quasar host galaxies still challenge the most powerful telescopes, instrumentation and processing techniques. Determining their basic morphological parameters and their integrated colours is feasible, but difficult, from imaging alone. However, detailed information on their stellar and gas contents and on their dynamics is achievable with deep spectroscopy. [less ▲]

Detailed reference viewed: 21 (2 ULg)
Full Text
Peer Reviewed
See detailCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses. II. SDSS J0924+0219: the redshift of the lensing galaxy, the quasar spectral variability and the Einstein rings
Eigenbrod, A.; Courbin, F.; Dye, S. et al

in Astronomy and Astrophysics (2006), 451

Aims.To provide the observational constraints required to use the gravitationally lensed quasar SDSS J0924+0219 for the determination of H[SUB]0[/SUB] from the time delay method. We measure here the ... [more ▼]

Aims.To provide the observational constraints required to use the gravitationally lensed quasar SDSS J0924+0219 for the determination of H[SUB]0[/SUB] from the time delay method. We measure here the redshift of the lensing galaxy, we show the spectral variability of the source, and we resolve the lensed host galaxy of the source. <BR />Methods.We present our VLT/FORS1 deep spectroscopic observations of the lensed quasar SDSS J0924+0219, as well as archival HST/NICMOS and ACS images of the same object. The two-epoch spectra, obtained in the Multi Object Spectroscopy (MOS) mode, allow for very accurate flux calibration and spatial deconvolution. This strategy provides spectra for the lensing galaxy and for the quasar images A and B, free of any mutual light contamination. We deconvolve the HST images as well, which reveal a double Einstein ring. The mass distributions in the lens, reconstructed in several ways, are compared. <BR />Results.We determine the redshift of the lensing galaxy in SDSS J0924+0219: z_lens = 0.394±0.001. Only slight spectral variability is seen in the continuum of quasar images A and B, while the C III] , Mg II and Fe II emission lines display obvious changes. The flux ratio between the quasar images A and B is the same in the emission lines and in the continuum. One of the Einstein rings found using deconvolution corresponds to the lensed quasar host galaxy at z=1.524 and a second bluer one, is the image either of a star-forming region in the host galaxy, or of another unrelated lower redshift object. A broad range of lens models give a satisfactory fit to the data. However, they predict very different time delays, making SDSS J0924+0219 an object of particular interest for photometric monitoring. In addition, the lens models reconstructed using exclusively the constraints from the Einstein rings, or using exclusively the astrometry of the quasar images, are not compatible. This suggests that multipole-like structures play an important role in SDSS J0924+0219. <BR /> [less ▲]

Detailed reference viewed: 29 (2 ULg)
Full Text
Peer Reviewed
See detailDiscovery of magnetic fields in the βCephei star ξ1 CMa and in several slowly pulsating B stars*
Hubrig, S.; Briquet, Maryline ULg; Schöller, M. et al

in Monthly Notices of the Royal Astronomical Society (2006), 369

We present the results of a magnetic survey of a sample of eight βCephei stars and 26 slowly pulsating B (SPBs) stars with the FOcal Reducer low dispersion Spectrograph at the Very Large Telescope. A weak ... [more ▼]

We present the results of a magnetic survey of a sample of eight βCephei stars and 26 slowly pulsating B (SPBs) stars with the FOcal Reducer low dispersion Spectrograph at the Very Large Telescope. A weak mean longitudinal magnetic field of the order of a few hundred Gauss is detected in the βCephei star ξ[SUP]1[/SUP]CMa and in 13 SPB stars. The star ξ[SUP]1[/SUP]CMa becomes the third magnetic star among the βCephei stars. Before our study, the star ζCas was the only known magnetic SPB star. All magnetic SPB stars for which we gathered several magnetic field measurements show a field that varies in time. We do not find a relation between the evolution of the magnetic field with stellar age in our small sample. Our observations imply that βCephei and SPB stars can no longer be considered as classes of non-magnetic pulsators, but the effect of the fields on the oscillation properties remains to be studied. [less ▲]

Detailed reference viewed: 2 (0 ULg)
Full Text
Peer Reviewed
See detailApplying the electronic nose in the environment : requirements for the instrument
Nicolas, Jacques ULg; Romain, Anne-Claude ULg; Delva, Julien

Conference (2006, June 01)

Applying the electronic nose to monitor environmental odours is not straightforward. The instrument must be adapted to the final objectives. It has to pass different steps : suitable sensor selection ... [more ▼]

Applying the electronic nose to monitor environmental odours is not straightforward. The instrument must be adapted to the final objectives. It has to pass different steps : suitable sensor selection, right choice of the target when supervised methods are used for data processing, choosing an odour-related dependant variable when using regressions, coping with the variability of environmental odour, taking the sensor drift into account, working only in concentrations above the limit of detection of the sensors, working with a mobile instrument in the field and coping with the ambient parameters. [less ▲]

Detailed reference viewed: 69 (45 ULg)
Full Text
Peer Reviewed
See detailValorisation of dietary fibre concentrate from date pulp.
Roiseux, Olivier; Blecker, Christophe ULg; Vanderbeke, E. et al

Poster (2006, June)

Detailed reference viewed: 2 (2 ULg)
Full Text
See detailPotential estimation of fatty acid content in cow milk by mid-infrared spectrometry
Soyeurt, Hélène ULg; Dardenne, Pierre; Lognay, Georges ULg et al

Conference (2006, June)

Detailed reference viewed: 26 (5 ULg)
Full Text
Peer Reviewed
See detailL’oracle et le messager. Fiction de l’interview chez Mallarmé
Durand, Pascal ULg

in Lieux Littéraires / La Revue (2006), 9/10

Detailed reference viewed: 31 (12 ULg)
Full Text
See detailExtraction and characterisation of a dietary fibre concentrate from date pulp
Roiseux, O.; Blecker, Christophe ULg; Besbes, S. et al

Poster (2006, June)

Detailed reference viewed: 15 (2 ULg)
Full Text
See detailPrêt public et droit d’auteur : le "droit de prêt", c’est pour bientôt
Habrand, Tanguy ULg

Article for general public (2006)

Detailed reference viewed: 10 (2 ULg)
Full Text
See detailIntegration of longevity into the Walloon genetic evaluation system
Vanderick, Sylvie ULg; Croquet, Coraline; Soyeurt, Hélène ULg et al

Conference (2006, June)

Detailed reference viewed: 30 (3 ULg)
Full Text
See detailEtat de l'Environnement Wallon – Chapitre "Odeur"
Nicolas, Jacques ULg

Report (2006)

The report constitutes a part of the Walloon Environmental status. It refers to environmental odours. It inventories the potential odour sources in Wallonia and presents the available data concerning ... [more ▼]

The report constitutes a part of the Walloon Environmental status. It refers to environmental odours. It inventories the potential odour sources in Wallonia and presents the available data concerning complaints and responses of the society to cope with the odour problems. [less ▲]

Detailed reference viewed: 22 (0 ULg)
Full Text
See detailContribution à l'état de l'environnement wallon - Partie : pollutions intérieures
Nicolas, Jacques ULg

Report (2006)

The document is a draft version for a contribution to the Walloon environmental state. It concerns the indoor air pollution. It inventory the possibles pollutants, their sources, their health risks, the ... [more ▼]

The document is a draft version for a contribution to the Walloon environmental state. It concerns the indoor air pollution. It inventory the possibles pollutants, their sources, their health risks, the methods to measure them and their actual guideline values. [less ▲]

Detailed reference viewed: 46 (2 ULg)
Full Text
Peer Reviewed
See detailRegulated discharge produces important changes of fish community in the grayling zone of a small salmonid stream.
Ovidio, Michaël ULg; Capra, Hervé; Orban, Patrice et al

Conference (2006, June)

Detailed reference viewed: 16 (4 ULg)
Full Text
Peer Reviewed
See detailModeling and computing ternary projective relations between regions
Clementini, Eliseo; Billen, Roland ULg

in IEEE Transactions on Knowledge and Data Engineering (2006), 18(6), 799-814

Current spatial database systems offer limited querying capabilities beyond binary topological relations. This paper introduces a model for projective relations between regions to support other ... [more ▼]

Current spatial database systems offer limited querying capabilities beyond binary topological relations. This paper introduces a model for projective relations between regions to support other qualitative spatial queries. The relations are ternary because they are based on the collinearity invariant of three points under projective geometry. The model is built on a partition of the plane into separate zones that are obtained from projective properties of two reference objects: Then, by considering the empty/ nonempty intersections of a primary object with these zones, the model is able to distinguish between 34 different projective relations. Then, the paper proposes original algorithms for computing the relations under the assumption that regions of the plane are stored as vector polygons in a spatial database. These algorithms run in optimal O(n log n) time. [less ▲]

Detailed reference viewed: 83 (18 ULg)