References of "Surdej, Jean"
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See detailCompared sensitivity of VLT, JWST and ELT for direct exoplanet detection in nearby stellar moving groups
Hanot, Charles ULg; Absil, Olivier ULg; Surdej, Jean ULg et al

in Villegas, Daniela; Kissler-Patig, Markus (Eds.) JWST and the ELTs: An ideal Combination (2010)

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast imaging has allowed direct images ... [more ▼]

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast imaging has allowed direct images of several exoplanetary systems to be taken (cf. HR 8799, Fomalhaut). In the near future, several new instruments are going to dramatically improve our sensitivity to exoplanet detection. Among these, SPHERE ( Spectro Polarimetric High contrast Exoplanet REsearch ) at the VLT, MIRI ( Mid Infra-Red Instrument) onboard JWST and the ELT will be equipped with coronagraphs to reveal faint objects in the vicinity of nearby stars. We made use of the Lyon group (COND) evolutionary models of young (sub-) stellar objects and exoplanets to compare the sensitivity of these different instruments using their estimated coronagraphic profiles. From this comparison, we present a catalogue of targets which are particularilly well suited for the different instruments. [less ▲]

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See detailEvolution des pratiques d'évaluation : le cas des sciences astrophysiques
Surdej, Jean ULg

Conference (2009, December 10)

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See detailPhysical Properties of the 0.94-Day Period Transiting Planetary System WASP-18
Southworth, John; Hinse, T. C.; Dominik, M. et al

in Astrophysical Journal (2009), 707

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we ... [more ▼]

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we achieve a photometric precision of 0.47-0.83 mmag per observation over complete transit events. The data are analyzed using the JKTEBOP code and three different sets of stellar evolutionary models. We find the mass and radius of the planet to be M [SUB]b[/SUB] = 10.43 ± 0.30 ± 0.24 M [SUB]Jup[/SUB] and R [SUB]b[/SUB] = 1.165 ± 0.055 ± 0.014 R [SUB]Jup[/SUB] (statistical and systematic errors), respectively. The systematic errors in the orbital separation and the stellar and planetary masses, arising from the use of theoretical predictions, are of a similar size to the statistical errors and set a limit on our understanding of the WASP-18 system. We point out that seven of the nine known massive transiting planets (M [SUB]b[/SUB] > 3 M [SUB]Jup[/SUB]) have eccentric orbits, whereas significant orbital eccentricity has been detected for only four of the 46 less-massive planets. This may indicate that there are two different populations of transiting planets, but could also be explained by observational biases. Further radial velocity observations of low-mass planets will make it possible to choose between these two scenarios. Based on data collected by MiNDSTEp with the Danish 1.54  m telescope at the ESO La Silla Observatory. [less ▲]

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See detailTransiting planetary system WASP-4 (Southworth+, 2009)
Southworth, J.; Hinse, T. C.; Burgdorf, M. J. et al

Textual, factual or bibliographical database (2009)

Light curves of four transit events of the transiting extrasolar planetary system WASP-4 are presented. The data were obtained using the Danish 1.5m telescope and DFOSC camera at ESO La Silla in 2008 ... [more ▼]

Light curves of four transit events of the transiting extrasolar planetary system WASP-4 are presented. The data were obtained using the Danish 1.5m telescope and DFOSC camera at ESO La Silla in 2008, with substantial telescope defocussing in order to improve the photometric precision of the observations. A Cousins R filter and exposure times of 120s were used. (1 data file). [less ▲]

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See detailHigh-precision photometry by telescope defocussing - II. The transiting planetary system WASP-4
Southworth, John; Hinse, T. C.; Burgdorf, M. J. et al

in Monthly Notices of the Royal Astronomical Society (2009)

We present and analyse light curves of four transits of the Southern hemisphere extrasolar planetary system WASP-4, obtained with a telescope defocused so the radius of each point spread function was 17 ... [more ▼]

We present and analyse light curves of four transits of the Southern hemisphere extrasolar planetary system WASP-4, obtained with a telescope defocused so the radius of each point spread function was 17 arcsec (44 pixels). This approach minimizes both random and systematic errors, allowing us to achieve scatters of between 0.60 and 0.88 mmag per observation over complete transit events. The light curves are augmented by published observations and analysed using the JKTEBOP code. The results of this process are combined with theoretical stellar model predictions to derive the physical properties of the WASP-4 system. We find that the mass and radius of the planet are M[SUB]b[/SUB] = 1.289[SUP]+0.090[/SUP][SUB]-0.090[/SUB][SUP]+0.039[/SUP][SUB]-0.000[/SUB]M[SUB]Jup[/SUB] and R[SUB]b[/SUB] = 1.371[SUP]+0.032[/SUP][SUB]-0.035[/SUB][SUP]+0.021[/SUP][SUB]-0.000[/SUB]R[SUB]Jup[/SUB], respectively (statistical and systematic uncertainties). These quantities give a surface gravity and density of g[SUB]b[/SUB] = 17.03[SUP]+0.97[/SUP][SUB]-0.54[/SUB]ms[SUP]-2[/SUP] and rho[SUB]b[/SUB] = 0.500[SUP]+0.032[/SUP][SUB]-0.021[/SUB][SUP]+0.000[/SUP][SUB]-0.008[/SUB] rho[SUB]Jup[/SUB], and fit the trends for short-period extrasolar planets to have relatively high masses and surface gravities. WASP-4 is now one of the best-quantified transiting extrasolar planetary systems, and significant further progress requires improvements to our understanding of the physical properties of low-mass stars. Based on data collected by MiNDSTEp with the Danish 1.54m telescope at the ESO La Silla Observatory. E-mail: jkt@astro.keele.ac.uk â ¡ Royal Society University Research Fellow. [less ▲]

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See detailHigh-precision photometry by telescope defocusing - I. The transiting planetary system WASP-5
Southworth, John; Hinse, T. C.; Jørgensen, U. G. et al

in Monthly Notices of the Royal Astronomical Society (2009), 396

We present high-precision photometry of two transit events of the extrasolar planetary system WASP-5, obtained with the Danish 1.54-m telescope at European Southern Obseratory La Silla. In order to ... [more ▼]

We present high-precision photometry of two transit events of the extrasolar planetary system WASP-5, obtained with the Danish 1.54-m telescope at European Southern Obseratory La Silla. In order to minimize both random and flat-fielding errors, we defocused the telescope so its point spread function approximated an annulus of diameter 40 pixel (16 arcsec). Data reduction was undertaken using standard aperture photometry plus an algorithm for optimally combining the ensemble of comparison stars. The resulting light curves have point-to-point scatters of 0.50mmag for the first transit and 0.59mmag for the second. We construct detailed signal-to-noise ratio calculations for defocused photometry, and apply them to our observations. We model the light curves with the JKTEBOP code and combine the results with tabulated predictions from theoretical stellar evolutionary models to derive the physical properties of the WASP-5 system. We find that the planet has a mass of M[SUB]b[/SUB] = 1.637 +/- 0.075 +/- 0.033M[SUB]Jup[/SUB], a radius of R[SUB]b[/SUB] = 1.171 +/- 0.056 +/- 0.012R [SUB]Jup[/SUB], a large surface gravity of g[SUB]b[/SUB] = 29.6 +/- 2.8ms[SUP]-2[/SUP] and a density of rho[SUB]b[/SUB] = 1.02 +/- 0.14 +/- 0.01rho[SUB]Jup[/SUB] (statistical and systematic uncertainties). The planet's high equilibrium temperature of T[SUB]eq[/SUB] = 1732 +/- 80K makes it a good candidate for detecting secondary eclipses. Based on data collected by Microlensing Network for the Detection of Small Terrestrial Exoplanets (MiNDSTEp) with the Danish 1.54-m telescope at the ESO La Silla Observatory. E-mail: j.k.taylor@warwick.ac.uk â ¡ Royal Society University Research Fellow. [less ▲]

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See detailExoplanet Characterization and the Search for Life
Kasting, James; Traub, W.; Roberge, A. et al

E-print/Working paper (2009)

Over 300 extrasolar planets (exoplanets) have been detected orbiting nearby stars. We now hope to conduct a census of all planets around nearby stars and to characterize their atmospheres and surfaces ... [more ▼]

Over 300 extrasolar planets (exoplanets) have been detected orbiting nearby stars. We now hope to conduct a census of all planets around nearby stars and to characterize their atmospheres and surfaces with spectroscopy. Rocky planets within their star's habitable zones have the highest priority, as these have the potential to harbor life. Our science goal is to find and characterize all nearby exoplanets; this requires that we measure the mass, orbit, and spectroscopic signature of each one at visible and infrared wavelengths. The techniques for doing this are at hand today. Within the decade we could answer long-standing questions about the evolution and nature of other planetary systems, and we could search for clues as to whether life exists elsewhere in our galactic neighborhood. [less ▲]

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See detailPEGASE, an infrared interferometer to study stellar environments and low mass companions around nearby stars
Ollivier, M.; Absil, Olivier ULg; Allard, F. et al

in Experimental Astronomy (2009), 23

PEGASE is a mission dedicated to the exploration of the environment (including habitable zone) of young and solar-type stars (particularly those in the DARWIN catalogue) and the observation of low mass ... [more ▼]

PEGASE is a mission dedicated to the exploration of the environment (including habitable zone) of young and solar-type stars (particularly those in the DARWIN catalogue) and the observation of low mass companions around nearby stars. It is a space interferometer project composed of three free flying spacecraft, respectively featuring two 40 cm siderostats and a beam combiner working in the visible and near infrared. It has been proposed to ESA as an answer to the first ``Cosmic Vision'' call for proposals, as an M mission. The concept also enables full-scale demonstration of space nulling interferometry operation for DARWIN. [less ▲]

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See detailA multi-wavelength survey of AGN in the XMM-LSS field. I. Quasar selection via the KX technique
Nakos, Theodoros; Willis, J. P.; Andreon, S. et al

in Astronomy and Astrophysics (2009), 494

Aims. We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg[SUP]2[/SUP] of the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey area where ... [more ▼]

Aims. We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg[SUP]2[/SUP] of the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey area where overlapping multi-wavelength imaging data permits an investigation of the physical nature of selected sources. Methods: The KX method identifies quasars on the basis of their optical (R and z') to near-infrared (K_s) photometry and point-like morphology. We combine these data with optical (u^*,g', r',i',z') and mid-infrared (3.6-24 mum) wavebands to reconstruct the spectral energy distributions (SEDs) of candidate quasars. Results: Of 93 sources selected as candidate quasars by the KX method, 25 are classified as quasars by the subsequent SED analysis. Spectroscopic observations are available for 12/25 of these sources and confirm the quasar hypothesis in each case. Even more, 90% of the SED-classified quasars show X-ray emission, a property not shared by any of the false candidates in the KX-selected sample. Applying a photometric redshift analysis to the sources without spectroscopy indicates that the 25 sources classified as quasars occupy the interval 0.7 <= z <= 2.5. The remaining 68/93 sources are classified as stars and unresolved galaxies. [less ▲]

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See detail2009 sera télescopique Le miroir liquide liégeois bientôt installé en Inde
Surdej, Jean ULg

Article for general public (2009)

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See detailTransiting planetary system WASP-5 (Southworth+, 2009)
Southworth, J.; Hinse, T~C; Jorgensen, U~G et al

Textual, factual or bibliographical database (2009)

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See detailThe International Liquid Mirror Telescope
Borra, Ermanno; Hickson, Paul; Surdej, Jean ULg

in Optics and Photonics News [= OPN] (2009), 20(4), 28-33

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See detailMilli-arcsecond Astrophysics with VSI, the VLTI Spectro-imager in the ELT Era
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Moorwood, Alan (Ed.) Science with the VLT in the ELT Era (2009)

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be ... [more ▼]

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be investigated at milli-arcsecond scales only with the VLT in its interferometric mode. We propose a spectro-imager, named VSI (VLTI spectro-imager), which is capable to probe these sources both over spatial and spectral scales in the near-infrared domain. This instrument will provide information complementary to what is obtained at the same time with ALMA at different wavelengths and the extreme large telescopes. [less ▲]

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See detailDiversity among other worlds: characterization of exoplanets by direct detection (Update of a White Paper submitted to the ESA ExoPlanet Roadmap Advisory Team)
Schneider, J.; Boccaletti, A.; Aylward, A. et al

Report (2008)

The physical characterization of exoplanets will require to take spectra at several orbital positions. For that purpose, a direct imaging capability is necessary. Direct imaging requires an efficient ... [more ▼]

The physical characterization of exoplanets will require to take spectra at several orbital positions. For that purpose, a direct imaging capability is necessary. Direct imaging requires an efficient stellar suppression mechanism, associated with an ultrasmooth telescope. We show that before future large space missions (interferometer, 4-8 m class coronograph, external occulter or Fresnel imager), direct imaging of giant planets and close-by super-Earth are at the cross-road of a high scientific interest and a reasonable feasibility. The scientific interest lies in the fact that super-Earths share common geophysical attributes with Earths. They already begin to be detected by radial velocity (RV) and, together with giant planets, they have a larger area than Earths, making them detectable with a 1.5-2 m class telescope in reflected light. We propose such a (space) telescope be a first step before large direct imaging missions. [less ▲]

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See detailGravitational Lensing, Dark Matter and the Optical Gravitational Lens Experiment
Surdej, Jean ULg; Claeskens, Jean-François ULg; Delacroix, Christian ULg et al

in Matagne, N.; Cugnon, Joseph; Lansberg, Jean-Philippe (Eds.) American Institute of Physics Conference Proc. Volume 1038 (2008, August 01)

After briefly reviewing the history of gravitational lensing, we recall the basic principles of the theory. We then describe and use a simple optical gravitational lens experiment which has the virtue of ... [more ▼]

After briefly reviewing the history of gravitational lensing, we recall the basic principles of the theory. We then describe and use a simple optical gravitational lens experiment which has the virtue of accounting for all types of image configurations observed so far among the presently known gravitational lens systems. Finally, we briefly present the 4m International Liquid Mirror Telescope project in the context of a photometric monitoring of multiply imaged quasars. [less ▲]

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See detailScience case for 1 mas spectro-imagining in the near-infrared
Garcia, Paulo J V; Berger, Jean-Phillipe; Marconi, Alessandro et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

We present the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data ... [more ▼]

We present the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data cubes in the near-infrared, with several spectral resolutions up to 12 000, by combining up to 8 VLTI telescopes. In the design of an instrument, the science case plays a central role by supporting the instrument construction decision, defining the top-level requirements and balancing design options. The overall science philosophy of VSI was that of a general user instrument serving a broad community. The science team addressed themes which included several areas of astrophysics and illustrated specific modes of operation of the instrument: a) YSO disks and winds; b) Multiplicity of young stars; c) Exoplanets; d) Debris disks; e) Stellar surface imaging; f) The environments of evolved stars; g) AGN tori; h) AGN's Broad Line Region; i) Supermassive black-holes; and j) Microlensing. The main conclusions can be summarized as follows: a) The accessible targets and related science are extremely sensitive to the instrument limiting magnitude; the instrument should be optimized for sensitivity and have its own fringe tracker. b) Most of the science cases are readily achievable with on-axis fringe tracking, off-axis fringe tracking enabling extra science. c) In most targets (YSOs, evolved stars and AGNs), the interpretation and analysis of circumstellar/nuclear dust morphology requires direct access to the gas via spectral resolved studies of emission lines, requiring at least a spectral resolution of 2 500. d) To routinely deliver images at the required sensitivity, the number of telescopes in determinant, with 6 telescopes being favored. e) The factorial increase in the number of closure phases and visibilities, gained in a single observation, makes massive surveys of parameters and related science for the first time possible. f) High dynamic range imaging and very high dynamic range differential closure phase are possible allowing the study of debris disks and characterization of pegasides. g) Spectro-imaging in the near-infrared is highly complementary to ALMA, adaptive optics and interferometric imaging in the thermal infrared. [less ▲]

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See detailVSI: the VLTI spectro-imager
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at ... [more ▼]

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions down to 1.1 milliarcsecond and spectral resolutions up to R = 12000. Targets as faint as K = 13 will be imaged without requiring a brighter nearby reference object; fainter targets can be accessed if a suitable reference is available. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral resolution enables a scientific program which serves a broad user community and at the same time provides the opportunity for breakthroughs in many areas of astrophysics. The high level specifications of the instrument are derived from a detailed science case based on the capability to obtain, for the first time, milliarcsecond-resolution images of a wide range of targets including: probing the initial conditions for planet formation in the AU-scale environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities using technologies which have been extensively tested in the past and VSI requires little in terms of new infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize the scientific return. [less ▲]

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See detailPhase closure image reconstruction for future VLTI instrumentation
Filho, Mercedes E; Renard, Stephanie; Garcia, Paulo et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

Classically, optical and near-infrared interferometry have relied on closure phase techniques to produce images. Such techniques allow us to achieve modest dynamic ranges. In order to test the feasibility ... [more ▼]

Classically, optical and near-infrared interferometry have relied on closure phase techniques to produce images. Such techniques allow us to achieve modest dynamic ranges. In order to test the feasibility of next generation optical interferometers in the context of the VLTI-spectro-imager (VSI), we have embarked on a study of image reconstruction and analysis. Our main aim was to test the influence of the number of telescopes, observing nights and distribution of the visibility points on the quality of the reconstructed images. Our results show that observations using six Auxiliary Telescopes (ATs) during one complete night yield the best results in general and is critical in most science cases; the number of telescopes is the determining factor in the image reconstruction outcome. In terms of imaging capabilities, an optical, six telescope VLTI-type configuration and ~200 meter baseline will achieve 4 mas spatial resolution, which is comparable to ALMA and almost 50 times better than JWST will achieve at 2.2 microns. Our results show that such an instrument will be capable of imaging, with unprecedented detail, a plethora of sources, ranging from complex stellar surfaces to microlensing events. [less ▲]

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See detailPhase referencing in optical interferometry
Filho, Mercedes E; Garcia, Paulo; Duvert, Gilles et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

One of the aims of next generation optical interferometric instrumentation is to be able to make use of information contained in the visibility phase to construct high dynamic range images. Radio and ... [more ▼]

One of the aims of next generation optical interferometric instrumentation is to be able to make use of information contained in the visibility phase to construct high dynamic range images. Radio and optical interferometry are at the two extremes of phase corruption by the atmosphere. While in radio it is possible to obtain calibrated phases for the science objects, in the optical this is currently not possible. Instead, optical interferometry has relied on closure phase techniques to produce images. Such techniques allow only to achieve modest dynamic ranges. However, with high contrast objects, for faint targets or when structure detail is needed, phase referencing techniques as used in radio interferometry, should theoretically achieve higher dynamic ranges for the same number of telescopes. Our approach is not to provide evidence either for or against the hypothesis that phase referenced imaging gives better dynamic range than closure phase imaging. Instead we wish to explore the potential of this technique for future optical interferometry and also because image reconstruction in the optical using phase referencing techniques has only been performed with limited success. We have generated simulated, noisy, complex visibility data, analogous to the signal produced in radio interferometers, using the VLTI as a template. We proceeded with image reconstruction using the radio image reconstruction algorithms contained in aips imagr (clean algorithm). Our results show that image reconstruction is successful in most of our science cases, yielding images with a 4 milliarcsecond resolution in K band. We have also investigated the number of target candidates for optical phase referencing. Using the 2MASS point source catalog, we show that there are several hundred objects with phase reference sources less than 30 arcseconds away, allowing to apply this technique. [less ▲]

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See detailHST observations of gravitationally lensed QSOs
Claeskens, Jean-François ULg; Sluse, Dominique ULg; Surdej, Jean ULg

in proceedings of the 41st ESLAB Symposium "The Impact of HST on European Astronomy" (June 2007) (2008, June)

Thanks to its sharp view, HST has significantly improved our knowledge of tens of gravitationally lensed quasars in four different respects: (1) confirming their lensed nature; (2) detecting the lensing ... [more ▼]

Thanks to its sharp view, HST has significantly improved our knowledge of tens of gravitationally lensed quasars in four different respects: (1) confirming their lensed nature; (2) detecting the lensing galaxy responsible for the image splitting; (3) improving the astrometric accuracy on the positions of the unresolved QSO images and of the lens; (4) resolving extended lensed structures from the QSO hosts into faint NIR or optical rings or arcs. These observations have helped to break some degeneracies on the lens potential, to probe the galaxy evolution and to reconstruct the true shape of the QSO host with an increased angular resolution. [less ▲]

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