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See detailDiscovery of a new spore assemblage in the Middle Devonian of Iberian Peninsula
Rial, Gonzalo; Cascales-Miñana, Borja ULg; Gozalo, Rodolfo et al

Conference (2015, July)

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See detailThe discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370
Hrudková, M.; Hatzes, A.; Karjalainen, R. et al

in Monthly Notices of the Royal Astronomical Society (2017), 464

We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 ± 1.0 M[SUB]Jupiter[/SUB] orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target ... [more ▼]

We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 ± 1.0 M[SUB]Jupiter[/SUB] orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our programme to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coudé echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph High Efficiency and Resolution Mercator Echelle Spectrograph of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 ± 4.5 d) variation with a semi-amplitude K = 133 ± 25 m s[SUP]- 1[/SUP], superimposed on a long-term trend. A low-mass stellar companion with an orbital period of ˜88 yr in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this system may answer this uncertainty. From Kepler photometry, we find that HD 175370 is most likely a low-mass red giant branch or asymptotic giant branch star. [less ▲]

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See detailDiscovery of a Probable Physical Triple Quasar
Djorgovski, S. G.; Courbin, F.; Meylan, G. et al

in Astrophysical Journal Letters (2007), 662

We report the discovery of the first known probable case of a physical triple quasar. A previously known double system, QQ 1429-008 at z=2.076, is shown to contain a third, fainter QSO component at the ... [more ▼]

We report the discovery of the first known probable case of a physical triple quasar. A previously known double system, QQ 1429-008 at z=2.076, is shown to contain a third, fainter QSO component at the same redshift. Deep optical and IR imaging has failed to reveal a plausible lensing galaxy group or a cluster, and we are unable to construct any viable lensing model that could lead to the observed distribution of source positions and relative intensities of the three QSO image components. There are also hints of differences in the broadband spectral energy distributions of the different components, which are more naturally understood if they are physically distinct active galactic nuclei (AGNs). Therefore, we conclude that this system is most likely a physical triple quasar, the first such close QSO grouping known at any redshift. The projected component separations are ~30-50 kpc, typical of interacting galaxy systems. The existence of this highly unusual system supports the standard picture in which galaxy interactions lead to the onset of QSO activity. Based in part on the data obtained at the W. M. Keck Observatory, a scientific partnership among the California Institue of Technology, the University of California, and NASA, made possible by the generous financial support of the W. M. Keck Foundation; data obtained with VLT/Antu telescope at ESO-Paranal Observatory; and data obtained with the Hubble Space Telescope (HST), operated by NASA. This research also made use of data obtained from the US National Virtual Observatory, which is sponsored by the NSF. [less ▲]

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See detailDiscovery of a Probable Triple Quasar
Djorgovski, Stanislav G.; Courbin, F.; Meylan, G. et al

Conference (2007, January)

We report the discovery of a first known probable case of a physical triple quasar (not a gravitational lens). A previously known double system, QQ 1429-008 at z = 2.076, is shown to contain a third ... [more ▼]

We report the discovery of a first known probable case of a physical triple quasar (not a gravitational lens). A previously known double system, QQ 1429-008 at z = 2.076, is shown to contain a third, fainter QSO component at the same redshift within the measurement errors. Deep optical and IR imaging at the Keck and VLT telescopes has failed to reveal a plausible lensing galaxy group or a cluster, and moreover, we are unable to construct any viable lensing model which could lead to the observed distribution of source positions and relative intensities of the three QSO image components. Therefore, we conclude that this system is most likely a physical triple quasar, the first such close grouping known at any redshift. The projected component separations in the restframe are 30 50 kpc for the standard concordance cosmology, typical of interacting galaxy systems. The existence of this highly unusual system supports the standard picture in which galaxy interactions lead to the onset of QSO activity. [less ▲]

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See detailDiscovery of a quadruply imaged quasar surrounded by a ring
Sluse, Dominique ULg; Claeskens, Jean-François ULg; Surdej, Jean ULg et al

Conference (2003, January)

Detailed reference viewed: 21 (8 ULg)
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See detailDiscovery of a quadruply lensed quasar - The 'clover leaf' H1413 + 117
Magain, Pierre ULg; Surdej, Jean ULg; Swings, J.-P. et al

in Nature (1988), 334

The authors report the discovery of a second gravitational lens system in the broad absorption line quasar H1413+117. Four images of comparable brightness are seen, separated by â ¡1 arcsec. The unique ... [more ▼]

The authors report the discovery of a second gravitational lens system in the broad absorption line quasar H1413+117. Four images of comparable brightness are seen, separated by â ¡1 arcsec. The unique configuration of the images, together with the fairly rare occurrence of this type of quasar, makes it incontrovertible that this is a lensed system, not a cluster of quasars. (See also 159.062). [less ▲]

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See detailDiscovery of a ring around Neptune
Haefner, R.; Manfroid, Jean ULg

Article for general public (1985)

The history of the discovery of Neptune and of the rings of Uranus is briefly reviewed, and the discovery of a ring around Neptune is described. The determination of some ring parameters is reported ... [more ▼]

The history of the discovery of Neptune and of the rings of Uranus is briefly reviewed, and the discovery of a ring around Neptune is described. The determination of some ring parameters is reported. Significant questions posed by the observations, e.g., why detections did not always occur when the ring zone passed in front of a star, are discussed. [less ▲]

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See detailDiscovery of a woman portrait behind La Violoniste by Kees Van Dongen through hyperspectral imaging
Herens, Elodie ULg; Defeyt, Catherine ULg; Walter, Philippe et al

in Heritage Science (2017), 5(14),

Despite the fact that Kees Van Dongen was one of the most famous painter of the 20th century, only little information about his palette and his technique is available. To contribute to the ... [more ▼]

Despite the fact that Kees Van Dongen was one of the most famous painter of the 20th century, only little information about his palette and his technique is available. To contribute to the characterization of Van Dongen's painting materials, La Violoniste, painted by the artist around 1923, has been analyzed by using three complementary techniques: macro X-ray fluorescence (MA-XRF), Raman spectroscopy and hyperspectral imaging. The elemental repartition given by MA-XRF and the results obtained thanks to Raman spectroscopy help us to complete the identification of pigments contained in La Violoniste (lead white, iron oxides, cadmium yellow, vermilion, Prussian blue, titanium white, ultramarine, a chromium pigment and carbon black) while the results obtained via hyperspectral imaging reveal a hidden woman portrait. Besides the fact that Kees Van Dongen was particularly renowned for his female portraits, this hidden composition presents obvious stylistic similarities with the well-known portraits produced by the artist during his Parisian stay (starting from 1899). Thanks to Raman spectroscopy, visual examination and MA-XRF, we show that the original background contains ultramarine, the hidden portrait's clothes are probably made of the same colour as the present violinist's dress and her carnation contains zinc, contrary to the violinist's flesh which is mainly made of lead white. [less ▲]

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See detailDiscovery of concentric broken rings at sub-arcsec separations in the HD 141569A gas-rich, debris disk with VLT/SPHERE
Perrot, C.; Boccaletti, A.; Pantin, E. et al

in Astronomy and Astrophysics (2016), 590

Context. Transition disks correspond to a short stage between the young protoplanetary phase and older debris phase. Along this evolutionary sequence, the gas component disappears leaving room for a dust ... [more ▼]

Context. Transition disks correspond to a short stage between the young protoplanetary phase and older debris phase. Along this evolutionary sequence, the gas component disappears leaving room for a dust-dominated environment where already-formed planets signpost their gravitational perturbations. <BR /> Aims: We endeavor to study the very inner region of the well-known and complex debris, but still gas-rich disk, around HD 141569A using the exquisite high-contrast capability of SPHERE at the VLT. Recent near-infrared (IR) images suggest a relatively depleted cavity within ~200 au, while former mid-IR data indicate the presence of dust at separations shorter than ~100 au. <BR /> Methods: We obtained multi-wavelength images in the near-IR in J, H2, H3 and Ks-bands with the IRDIS camera and a 0.95-1.35 μm spectral data cube with the IFS. Data were acquired in pupil-tracking mode, thus allowing for angular differential imaging. <BR /> Results: We discovered several new structures inside 1'', of which the most prominent is a bright ring with sharp edges (semi-major axis: 0.4'') featuring a strong north-south brightness asymmetry. Other faint structures are also detected from 0.4'' to 1'' in the form of concentric ringlets and at least one spiral arm. Finally, the VISIR data at 8.6 μm suggests the presence of an additional dust population closer in. Besides, we do not detect companions more massive than 1-3 mass of Jupiter. <BR /> Conclusions: The performance of SPHERE allows us to resolve the extended dust component, which was previously detected at thermal and visible wavelengths, into very complex patterns with strong asymmetries; the nature of these asymmetries remains to be understood. Scenarios involving shepherding by planets or dust-gas interactions will have to be tested against these observations. Based on data collected at the European Southern Observatory, Chile, ESO programs 095.C-0381 and 095.C-0298. [less ▲]

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See detailDiscovery of Diffure Aurora on Mars
Stiepen, Arnaud ULg; Schneider; Jain et al

Conference (2015, September)

The Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2014) onboard the MAVEN spacecraft has discovered diffuse aurora in Mars’ northern hemisphere spanning a wide range of geographic latitudes ... [more ▼]

The Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2014) onboard the MAVEN spacecraft has discovered diffuse aurora in Mars’ northern hemisphere spanning a wide range of geographic latitudes and longitudes (Figure 1). This widespread aurora differs from the small auroral patches discovered by the SPICAM instrument onboard the Mars Express spacecraft (Bertaux et al., 2005; Leblanc et al., 2008; Gérard et al., submitted; Soret et al., submitted) restricted to regions of crustal magnetic fields in the southern hemisphere. Furthermore, the northern diffuse aurora appears to peak at altitudes below 100 km, while the crustal field aurora peaked around 120 km. [less ▲]

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See detailDiscovery of diffuse aurora on Mars
Schneider, N. M.; Deighan, J. I.; Jain, S. K. et al

in Science (2015), 350(6261),

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern ... [more ▼]

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern hemisphere, coincident with a solar energetic particle outburst. The Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, detected auroral emission in virtually all nightside observations for ~5 days, spanning nearly all geographic longitudes. Emission extended down to ~60 kilometer (km) altitude (1 microbar), deeper than confirmed at any other planet. Solar energetic particles were observed up to 200 kilo-electron volts; these particles are capable of penetrating down to the 60 km altitude. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit auroras more globally than Earth. [less ▲]

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See detailDiscovery of Diffuse Aurora on Mars
Schneider, Nick; Stiepen, Arnaud ULg; Jain, S et al

Conference (2015)

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See detailDiscovery of English Grain Aphid (Hemiptera: Aphididae) Biotypes in China
Xu, Zhao-Huan; Chen, Julian; Cheng, Deng-Fa et al

in Journal of Economic Entomology (2011), 104(3), 1080-1086

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See detailDiscovery of Magnetic Fields in Slowly Pulsating B Stars
Hubrig, S.; Briquet, Maryline ULg; Schöller, M. et al

in Active OB-Stars: Laboratories for Stellar and Circumstellar Physics, ASP Conference Series, Vol. 361, Proceedings of the conference held 29 August - 2 September, 2005 at Hokkai-Gakuen University, Sapporo, Japan. (2007, March 01)

We present the first observations and conclusions of a magnetic survey with FORS 1 at the VLT of a sample of 25 Slowly Pulsating B stars. A clear mean longitudinal magnetic field of the order of a few ... [more ▼]

We present the first observations and conclusions of a magnetic survey with FORS 1 at the VLT of a sample of 25 Slowly Pulsating B stars. A clear mean longitudinal magnetic field of the order of a few hundred Gauss was detected in eleven SPBs. Among them several SPBs show a magnetic field that varies in time. It becomes clear that SPBs cannot be regarded anymore as non-magnetic stars. [less ▲]

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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 ▲]

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See detailDiscovery of magnetic fields in three He variable Bp stars with He and Si spots
Briquet, Maryline ULg; Hubrig, S.; Schöller, M. et al

in Astronomische Nachrichten (2007), 328

It is essential for the understanding of stellar structure models of high mass stars to explain why constant stars, non-pulsating chemically peculiar hot Bp stars and pulsating stars co-exist in the ... [more ▼]

It is essential for the understanding of stellar structure models of high mass stars to explain why constant stars, non-pulsating chemically peculiar hot Bp stars and pulsating stars co-exist in the slowly pulsating B stars and β Cephei instability strips. We have conducted a search for magnetic fields in the four Bp stars HD 55522, HD 105382, HD 131120, and HD 138769 which previously have been wrongly identified as slowly pulsating B stars. A recent study of these stars using the Doppler Imaging technique revealed that the elements He and Si are inhomogeneously distributed on the stellar surface, causing the periodic variability. Using FORS 1 in spectropolarimetric mode at the VLT, we have acquired circular polarisation spectra to test the presence of a magnetic field in these stars. A variable magnetic field is clearly detected in HD 55522 and HD 105382, but no evidence for the existence of a magnetic field was found in HD 131120. The presence of a magnetic field in HD 138769 is suggested by one measurement at 3 σ level. We discuss the occurrence of magnetic B stars among the confirmed pulsating B stars and find strong magnetic fields of order kG and oscillations to be mutually exclusive. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO programmes 71.D-0308(A), 072.D-0377(A), and 073.D-0466(A)). [less ▲]

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See detailDiscovery of Neptune's ring at La Silla
Haefner, R.; Manfroid, Jean ULg; Bouchet, P.

in The Messenger (1985), 42

The unexpected rediscovery of the Uranian rings in 1977 and the discovery of the faint Jovian rings in 1979 led to an intensified search for rings around Neptune. A description is given of observing ... [more ▼]

The unexpected rediscovery of the Uranian rings in 1977 and the discovery of the faint Jovian rings in 1979 led to an intensified search for rings around Neptune. A description is given of observing programs at the European Southern Observatory (ESO) in Chile, which led to a discovery of such a ring, taking into account the utilization of the ESO 0.5 m and 1 m telescopes. The discovery is based on observations made on the night of July 22, 1984, in connection with a stellar occultation by the planet. Explanations for the observed differences in shape and timing of the occultation event, as recorded by both telescopes, are discussed. The obtained conclusions could be confirmed by a study of the results of a group of American astronomers working at the Cerro Tololo observatory. The observations strongly favor the existence of, at least, a part of a ring which has a width of roughly 10-15 km over a length of at least 100 km. [less ▲]

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See detailDiscovery of New Inhibitors of Resistant Streptococcus pneumoniae Penicillin Binding Protein (PBP) 2x by Structure-Based Virtual Screening.
Miguet, Laurence; Zervosen, Astrid ULg; Gerards, Thomas ULg et al

in Journal of Medicinal Chemistry (2009)

Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer constitutive of the bacterial envelope. They have been targeted for more than half a century by extensively ... [more ▼]

Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer constitutive of the bacterial envelope. They have been targeted for more than half a century by extensively derived molecular scaffolds of penicillins and cephalosporins. Streptococcus pneumoniae resists the antibiotic pressure by inducing highly mutated PBPs that can no longer bind the beta-lactam containing agents. To find inhibitors of PBP2x from Streptococcus pneumoniae (spPBP2x) with novel chemical scaffold so as to circumvent the resistance problems, a hierarchical virtual screening procedure was performed on the NCI database containing approximately 260000 compounds. The calculations involved ligand-based pharmacophore mapping studies and molecular docking simulations in a homology model of spPBP2x from the highly resistant strain 5204. A total of 160 hits were found, and 55 were available for experimental tests. Three compounds harboring two novel chemical scaffolds were identified as inhibitors of the resistant strain 5204-spPBP2x at the micromolar range. [less ▲]

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