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See detailThe discovery and properties of pentaquarks
Stancu, Floarea ULg

in International Journal of Modern Physics A : Particles & Fields, Gravitation, Cosmology, Nuclear Physics (2005), 20(2-3), 209-218

The pentaquarks are exotic baryons formed of four quarks and an antiquarks. Their existence has been discussed in the literature over the last 30 years or more, first in connection with kaon nucleon ... [more ▼]

The pentaquarks are exotic baryons formed of four quarks and an antiquarks. Their existence has been discussed in the literature over the last 30 years or more, first in connection with kaon nucleon scattering data. The subject has been revived by the end of 2002 when experimental evidence of a narrow baryon of strangeness S = +1, and mass M similar or equal to 1530 MeV has been found. This is interpreted as the lightest member of an SU(3)-flavor antidecuplet. Here we shall mainly review the predictions of pentaquark properties as e.g. mass, spin and parity, within constituent quark models. Both light and heavy pentaquarks will be presented. [less ▲]

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See detailDiscovery en de WHPC (case note : Commercial Court of Termonde - 3 January 2000
Wautelet, Patrick ULg

in Revue de Droit Commercial Belge [= RDC] = Tijdschrift voor Belgisch Handelsrecht [=TBH] (2000)

In this short comment on a decision issued by the Commercial Court of Termonde, I offer some thoughts on the possibility for a business established in Belgium to seek protection in Belgium against ... [more ▼]

In this short comment on a decision issued by the Commercial Court of Termonde, I offer some thoughts on the possibility for a business established in Belgium to seek protection in Belgium against discovery proceedings in which it is involved before a court in the US. In the case commented, the court refused the relief sought mainly because it found that enjoining the defendant would constitute undue influence in the proceedings pending in the US. [less ▲]

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See detailDiscovery of a bright quasar without a massive host galaxy
Magain, Pierre ULg; Letawe, Géraldine ULg; Courbin, F. et al

in Nature (2005), 437(7057), 381-384

A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy(1,2). Because the optical luminosity of quasars exceeds that of their host galaxy ... [more ▼]

A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy(1,2). Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars(3-7). Since then, the connection between quasars and galaxies has been well established(8). Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected(8,9) for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole. [less ▲]

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See detailDiscovery of a Companion Candidate in the HD 169142 Transition Disk and the Possibility of Multiple Planet Formation
Reggiani, Maddalena; Quanz, Sascha P.; Meyer, Michael R. et al

in Astrophysical Journal Letters (2014), 792

We present L'- and J-band high-contrast observations of HD 169142, obtained with the Very Large Telescope/NACO AGPM vector vortex coronagraph and the Gemini Planet Imager, respectively. A source located ... [more ▼]

We present L'- and J-band high-contrast observations of HD 169142, obtained with the Very Large Telescope/NACO AGPM vector vortex coronagraph and the Gemini Planet Imager, respectively. A source located at 0.''156 ± 0.''032 north of the host star (P.A. = 7.4° ± 11.3°) appears in the final reduced L' image. At the distance of the star (~145 pc), this angular separation corresponds to a physical separation of 22.7 ± 4.7 AU, locating the source within the recently resolved inner cavity of the transition disk. The source has a brightness of L' = 12.2 ± 0.5 mag, whereas it is not detected in the J band (J >13.8 mag). If its L' brightness arose solely from the photosphere of a companion and given the J - L' color constraints, it would correspond to a 28-32 MJup object at the age of the star, according to the COND models. Ongoing accretion activity of the star suggests, however, that gas is left in the inner disk cavity from which the companion could also be accreting. In this case, the object could be lower in mass and its luminosity enhanced by the accretion process and by a circumplanetary disk. A lower-mass object is more consistent with the observed cavity width. Finally, the observations enable us to place an upper limit on the L'-band flux of a second companion candidate orbiting in the disk annular gap at ~50 AU, as suggested by millimeter observations. If the second companion is also confirmed, HD 169142 might be forming a planetary system, with at least two companions opening gaps and possibly interacting with each other. [less ▲]

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See detailDiscovery of a Lochkovian flora (Lower Devonian) in the Iberian Peninsula
Cascales - Miñana, Borja ULg; Martínez-Pérez, Carlos; Botella, Héctor

in Geodiversitas (2011), 33(1), 33-41

The Lower Devonian represents an important episode in plant life history, which was marked by the diversification of land plants. Unfortunately, remains of early Devonian plants in the Iberian Peninsula ... [more ▼]

The Lower Devonian represents an important episode in plant life history, which was marked by the diversification of land plants. Unfortunately, remains of early Devonian plants in the Iberian Peninsula are scarce. In the present paper, we describe a small assemblage of early land plants from the Lochkovian (Lower Devonian) of the Teruel Province in Spain. The main element consists of Taeniocrada-like sterile stems that are predominantly dichotomous and ribbon-like with a narrow central strand. An unidentified fossil formed by dichotomous axes together with an uncertain globular structure were also observed. This finding increases our knowledge of the palaeogeographical distribution of early land plants. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris. [less ▲]

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See detailDiscovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317
Briquet, Maryline ULg; Neiner, C.; Leroy, B. et al

in Astronomy and Astrophysics (2013), 557

Context. A promising way of testing the impact of a magnetic field on internal mixing (core overshooting, internal rotation) in main-sequence B-type stars is to perform asteroseismic studies of a sample ... [more ▼]

Context. A promising way of testing the impact of a magnetic field on internal mixing (core overshooting, internal rotation) in main-sequence B-type stars is to perform asteroseismic studies of a sample of magnetic pulsators. <BR /> Aims: The CoRoT satellite revealed that the B3IV star HD 43317 is a hybrid SPB/β Cep-type pulsator that has a wealth of pulsational constraints on which one can perform a seismic modelling, in particular, probing the extent of its convective core and mixing processes. Moreover, indirect indicators of a magnetic field in the star were observed: rotational modulation due to chemical or temperature spots and X-ray emission. Our goal was to directly investigate the field in HD 43317 and, if it is magnetic, to characterise it. <BR /> Methods: We collected data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL, Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from HD 43317. We modelled the longitudinal field measurements directly with a dipole. <BR /> Results: Zeeman signatures in the Stokes V profiles of HD 43317 are clearly detected and rotationally modulated, which proves that this star exhibits an oblique magnetic field. The modulation with the rotation period deduced from the CoRoT light curve is also confirmed, and we found a field strength at the poles of about 1 kG. Our result must be taken into account in future seismic modelling work of this star. Based on observations obtained using the Narval spectropolarimeter at the Observatoire du Pic du Midi (France), which is operated by the Institut National des Sciences de l'Univers (INSU). [less ▲]

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See detailDiscovery of a magnetic field in the rapidly rotating O-type secondary of the colliding-wind binary HD 47129 (Plaskett's star)
Grunhut, J. H.; Wade, G. A.; Leutenegger, M. et al

in Monthly Notices of the Royal Astronomical Society (2013), 428

We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context ... [more ▼]

We report the detection of a strong, organized magnetic field in the secondary component of the massive O8III/I+O7.5V/III double-lined spectroscopic binary system HD 47129 (Plaskett's star) in the context of the Magnetism in Massive Stars survey. Eight independent Stokes V observations were acquired using the Echelle SpectroPolarimetric Device for the Observations of Stars (ESPaDOnS) spectropolarimeter at the Canada-France-Hawaii Telescope and the Narval spectropolarimeter at the Télescope Bernard Lyot. Using least-squares deconvolution we obtain definite detections of signal in Stokes V in three observations. No significant signal is detected in the diagnostic null (N) spectra. The Zeeman signatures are broad and track the radial velocity of the secondary component; we therefore conclude that the rapidly rotating secondary component is the magnetized star. Correcting the polarized spectra for the line and continuum of the (sharp-lined) primary, we measured the longitudinal magnetic field from each observation. The longitudinal field of the secondary is variable and exhibits extreme values of -810 ± 150 and +680 ± 190 G, implying a minimum surface dipole polar strength of 2850 ± 500 G. In contrast, we derive an upper limit (3σ) to the primary's surface magnetic field of 230 G. The combination of a strong magnetic field and rapid rotation leads us to conclude that the secondary hosts a centrifugal magnetosphere fed through a magnetically confined wind. We revisit the properties of the optical line profiles and X-ray emission - previously interpreted as a consequence of colliding stellar winds - in this context. We conclude that HD 47129 represents a heretofore unique stellar system - a close, massive binary with a rapidly rotating, magnetized component - that will be a rich target for further study. [less ▲]

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See detailDiscovery of a Mississippian Reef in Turkey: The Upper Viséan Microbial-Sponge-Bryozoan-Coral Bioherm from Kongul Yayla (Taurides, S Turkey)
Denayer, Julien ULg; Aretz, Markus

in Turkish Journal of Earth Sciences (2012), 21(3), 375-389

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See detailDiscovery of a natural thiamine adenine nucleotide
Bettendorff, Lucien ULg; Wirtzfeld, Barbara; Makarchikov, Alexander F et al

in Nature Chemical Biology (2007), 3(4), 211-212

Several important cofactors are adenine nucleotides with a vitamin as the catalytic moiety. Here, we report the discovery of the first adenine nucleotide containing vitamin B1: adenosine thiamine ... [more ▼]

Several important cofactors are adenine nucleotides with a vitamin as the catalytic moiety. Here, we report the discovery of the first adenine nucleotide containing vitamin B1: adenosine thiamine triphosphate (AThTP, 1), or thiaminylated ATP. We discovered AThTP in Escherichia coli and found that it accumulates specifically in response to carbon starvation, thereby acting as a signal rather than a cofactor. We detected smaller amounts in yeast and in plant and animal tissues. [less ▲]

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See detailDiscovery of a New AM CVn System with the Kepler Satellite
Fontaine, G.; Brassard, P.; Green, E. M. et al

in Astrophysical Journal (2011), 726

We report the discovery of a new AM CVn system on the basis of broadband photometry obtained with the Kepler satellite supplemented by ground-based optical spectroscopy. Initially retained on Kepler ... [more ▼]

We report the discovery of a new AM CVn system on the basis of broadband photometry obtained with the Kepler satellite supplemented by ground-based optical spectroscopy. Initially retained on Kepler target lists as a potential compact pulsator, the blue object SDSS J190817.07+394036.4 (KIC 004547333) has turned out to be a high-state AM CVn star showing the He-dominated spectrum of its accretion disk significantly reddened by interstellar absorption. We constructed new grids of NLTE synthetic spectra for accretion disks in order to analyze our spectroscopic observations. From this analysis, we infer preliminary estimates of the rate of mass transfer, the inclination angle of the disk, and the distance to the system. The AM CVn nature of the system is also evident in the Kepler light curve, from which we extracted 11 secure periodicities. The luminosity variations are dominated by a basic periodicity of 938.507 s, likely to correspond to a superhump modulation. The light curve folded on the period of 938.507 s exhibits a pulse shape that is very similar to the superhump wavefront seen in AM CVn itself, which is a high-state system and the prototype of the class. Our Fourier analysis also suggests the likely presence of a quasi-periodic oscillation similar to those already observed in some high-state AM CVn systems. Furthermore, some very low-frequency, low-amplitude aperiodic photometric activity is likely present, which is in line with what is expected in accreting binary systems. Inspired by previous work, we further looked for and found some intriguing numerical relationships between the 11 secure detected frequencies, in the sense that we can account for all of them in terms of only three basic clocks. This is further evidence in favor of the AM CVn nature of the system. [less ▲]

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

in The 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)

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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 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, Nick; Stiepen, Arnaud ULg; Jain, S et al

Conference (2015)

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