References of "Surdej, Jean"      in Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others     Showing results 81 to 100 of 537     1 2 3 4 5 6 7 8 9 10     Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoringMancini, L.; Giacobbe, P.; Littlefair, S. P. et alin Astronomy and Astrophysics (2015), 584Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman 16AB is an ... [more ▼]Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman 16AB is an interesting target for such a study, because its components stand at the L/T transition and show high levels of variability. Luhman 16AB is also the third closest system to the solar system, which allows precise astrometric investigations with ground-based facilities. Aims. The aim of the work is to estimate the rotation period and study the astrometric motion of both components. Methods. We have monitored Luhman 16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54 m telescope at La Silla, through a special i + z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20 ± 0.02 mag and 0.34 ± 0.02 mag for Luhman 16A and 16B, respectively. Results. We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman 16B rotates with a period of 5.1 ± 0.1 h, in very good agreement with previous measurements. For Luhman 16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8 h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman 16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system. © ESO, 2015. [less ▲]Detailed reference viewed: 17 (0 ULiège) A method to search for large-scale concavities in asteroid shape modelsDevogele, Maxime ; Rivet, Jean-Pierre; Tanga, Paolo et alin Monthly Notices of the Royal Astronomical Society (2015)Light curve inversion is proven to produce an unique model solution only under the hypothesis that the asteroid is convex. However, it was suggested that the resulting shape model, for the case of non ... [more ▼]Light curve inversion is proven to produce an unique model solution only under the hypothesis that the asteroid is convex. However, it was suggested that the resulting shape model, for the case of non-convex asteroid, is the convex-hull of the true asteroid non-convex shape. While a convex shape is already useful to provide the overall aspect of the target, much information about real shapes is missed, as we know that asteroids are very irregular. It is a commonly accepted evidence that large flat areas sometimes appearing on shapes derived from light curves correspond to concave areas, but this information has not been further explored and exploited so far. We present in this paper a method that allows to predict the presence of concavities from such flat regions. This method analyzes the distribution of the local normals to the facets composing shape models to predict the presence of abnormally large flat surfaces. In order to test our approach, we consider here its application to a large family of synthetic asteroid shapes, and to real asteroids with large scale concavities, whose detailed shape is known by other kinds of observations (radar and spacecraft encounters). The method that we propose is proven to be reliable and capable of providing a qualitative indication of the relevance of concavities on well-constrained asteroid shapes derived from purely photometric data sets. [less ▲]Detailed reference viewed: 42 (9 ULiège) Realizing the diamond annular groove phase masks for the mid infrared region: five years of successful process development of diamond plasma etchingForsberg, Pontus; Vargas Catalan, Ernesto; Delacroix, Christian et alin Navarro, Ramon; Cunningham, Colin; Barto, Allison (Eds.) Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation (2014, August 07)The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in ... [more ▼]The Annular Groove Phase Mask (AGPM) is a circularly symmetric half wave plate consisting of a circular high aspect ratio sub-wavelength grating. Here we present a method for realizing such structures in diamond. To improve the AGPM performance, antireflective sub-wavelength gratings are etched on the backside of the components, and such gratings are also discussed. Components for the N-band (around 10 μm) and the L-band (around 3.8 μm) have been successfully fabricated. We are currently developing the process further to improve the precision of the gratings and produce an AGPM for the K-band (around 2.2 μm). © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. [less ▲]Detailed reference viewed: 24 (2 ULiège) The VORTEX project: first results and perspectivesAbsil, Olivier ; Mawet, Dimitri; Delacroix, Christian et alin Marchetti, Enrico; Close, Laird; Véran, Jean-Pierre (Eds.) Adaptive Optics Systems IV (2014, July 21)Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the ... [more ▼]Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They feature a very small inner working angle (down to the diffraction limit of the telescope), a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric sub-wavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about 6e-5 at 2λ/D. Three of them have now been installed on world-leading diffraction-limited infrared cameras, namely VLT/NACO, VLT/VISIR and LBT/LMIRCam. During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit (0.1"). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imager and on future extremely large telescopes (ELTs). In particular, we will briefly describe our current efforts to improve the manufacturing of mid-infrared AGPMs, to push their operation to shorter wavelengths, and to provide deeper starlight extinction by creating new designs for higher topological charge vortices. Within the VORTEX project, we also plan to develop new image processing techniques tailored to coronagraphic images, and to study some pre- and post-coronagraphic concepts adapted to the vortex coronagraph in order to reduce scattered starlight in the final images. [less ▲]Detailed reference viewed: 107 (49 ULiège) L'-band AGPM vector vortex coronagraph's first light on LBTI/LMIRCamDefrere, Denis ; Absil, Olivier ; Hinz, P. et alin Proceedings of SPIE - The International Society for Optical Engineering (2014, July 21)We present the first observations obtained with the L'-band AGPM vortex coronagraph recently installed on LBTI/LMIRCam. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from ... [more ▼]We present the first observations obtained with the L'-band AGPM vortex coronagraph recently installed on LBTI/LMIRCam. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from diamond subwavelength gratings. It is designed to improve the sensitivity and dynamic range of high-resolution imaging at very small inner working angles, down to 0.09 arcseconds in the case of LBTI/LMIRCam in the L' band. During the first hours on sky, we observed the young A5V star HR8799 with the goal to demonstrate the AGPM performance and assess its relevance for the ongoing LBTI planet survey (LEECH). Preliminary analyses of the data reveal the four known planets clearly at high SNR and provide unprecedented sensitivity limits in the inner planetary system (down to the diffraction limit of 0.09 arcseconds). © 2014 SPIE. [less ▲]Detailed reference viewed: 28 (8 ULiège) The VORTEX coronagraphic test benchJolivet, Aïssa ; Piron, Pierre ; Huby, Elsa et alin Navarro, Ramon; Cunningham, Colin; Barto, Allison (Eds.) Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation (2014, July 18)In this paper, we present the infrared coronagraphic test bench of the University of Liège named VODCA (Vortex Optical Demonstrator for Coronagraphic Applications). The goal of the bench is to assess the ... [more ▼]In this paper, we present the infrared coronagraphic test bench of the University of Liège named VODCA (Vortex Optical Demonstrator for Coronagraphic Applications). The goal of the bench is to assess the performances of the Annular Groove Phase Masks (AGPMs) at near- to mid-infrared wavelengths. The AGPM is a subwavelength grating vortex coronagraph of charge two (SGVC2) made out of diamond. The bench is designed to be completely achromatic and will be composed of a super continuum laser source emitting in the near to mid-infrared, several parabolas, diaphragms and an infrared camera. This way, we will be able to test the different AGPMs in the M, L, K and H bands. Eventually, the bench will also allow the computation of the incident wavefront aberrations on the coronagraph. A reflective Lyot stop will send most of the stellar light to a second camera to perform low-order wavefront sensing. This second system coupled with a deformable mirror will allow the correction of the wavefront aberrations. We also aim to test other pre- and/or post-coronagraphic concepts such as optimal apodization. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. [less ▲]Detailed reference viewed: 55 (12 ULiège) Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)Delacroix, Christian ; Absil, Olivier ; Carlomagno, Brunella et alin Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal ... [more ▼]One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2pi radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation. [less ▲]Detailed reference viewed: 35 (6 ULiège) Mid-IR AGPMs for ELT applicationsCarlomagno, Brunella ; Delacroix, Christian ; Absil, Olivier et alin Ramsay, Suzanne; McLean, Ian; Takami, Hideki (Eds.) Ground-based and Airborne Instrumentation for Astronomy V (2014, July 08)The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This ... [more ▼]The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument. [less ▲]Detailed reference viewed: 34 (9 ULiège) Peculiar polarization and shape properties of Barbarian asteroids: A campaign for their physical characterizationDevogele, Maxime ; Hanus, J.; Tanga, P. et alConference (2014, July)A few years ago, asteroid polarimetry allowed to discover a class of asteroids exhibiting peculiar phase polarization curves, collectively called "Barbarians" (a dozen are known) from the prototype of ... [more ▼]A few years ago, asteroid polarimetry allowed to discover a class of asteroids exhibiting peculiar phase polarization curves, collectively called "Barbarians" (a dozen are known) from the prototype of this class, the asteroid (234) Barbara. All such objects belong to the taxonomic classes L, Ld, and K, all related to the general S-complex. However, the "Barbarian" polarimetric properties are not found among all known L-class asteroids. Therefore, we cannot be sure that composition is the only and one responsible of the wide negative polarization branch. On the other hand, it was also suggested that a peculiar distribution of incidence/diffusion angles, resulting from the presence of large concavities on the object surface, could play a role in the polarimetric behaviour. Based on such motivations, we are running a systematic campaign for shape determination at the C2PU telescope of the Observatoire de la Côte d'Azur (Calern site) and several other sites in the world. By using photometric inversion techniques we hope to obtain indications on the presence of concavities. [less ▲]Detailed reference viewed: 23 (3 ULiège) Observing the Sun with micro-interferometric devices: a didactic experimentDefrere, Denis ; Absil, Olivier ; Hanot, C. et alin Surdej, Jean; Le Coroller, Hervé; Arnold, Luc (Eds.) Improving the Performances of Current Optical Interferometers & Future Designs (2014, April 01)Measuring the angular diameter of celestial bodies has long been the main purpose of stellar interferometry and was its historical motivation. Nowadays, stellar interferometry is widely used for various ... [more ▼]Measuring the angular diameter of celestial bodies has long been the main purpose of stellar interferometry and was its historical motivation. Nowadays, stellar interferometry is widely used for various other scientific purposes that require very high angular resolution measurements. In terms of angular spatial scales probed, o [less ▲]Detailed reference viewed: 107 (6 ULiège) L'-band AGPM vector vortex coronagraph's first light on LBTI/LMIRCAMDefrere, Denis ; Absil, Olivier ; Hinz, P. et alPoster (2014, March)We present the first science observations obtained with the L'-band AGPM coronagraph recently installed on LBTI/LMIRCAM. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from ... [more ▼]We present the first science observations obtained with the L'-band AGPM coronagraph recently installed on LBTI/LMIRCAM. The AGPM (Annular Groove Phase Mask) is a vector vortex coronagraph made from diamond sub-wavelength gratings tuned to the L'-band. It is designed to improve the sensitivity and dynamic range of high-resolution imaging at very small inner working a [less ▲]Detailed reference viewed: 48 (10 ULiège) Physical properties and transmission spectrum of the WASP-80 planetary system from multi-colour photometryMancini, L.; Southworth, J.; Ciceri, S. et alin Astronomy and Astrophysics (2014), 562WASP-80 is one of only two systems known to contain a hot Jupiter which transits its M-dwarf host star. We present eight light curves of one transit event, obtained simultaneously using two defocussed ... [more ▼]WASP-80 is one of only two systems known to contain a hot Jupiter which transits its M-dwarf host star. We present eight light curves of one transit event, obtained simultaneously using two defocussed telescopes. These data were taken through the Bessell I, Sloan g'r'i'z' and near-infrared JHK passbands. We use our data to search for opacity-induced changes in the planetary radius, but find that all values agree with each other. Our data are therefore consistent with a flat transmission spectrum to within the observational uncertainties. We also measure an activity index of the host star of log R '[SUB]HK[/SUB] = -4.495, meaning that WASP-80 A shows strong chromospheric activity. The non-detection of starspots implies that, if they exist, they must be small and symmetrically distributed on the stellar surface. We model all available optical transit light curves and obtain improved physical properties and orbital ephemerides for the system. Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A126 [less ▲]Detailed reference viewed: 20 (0 ULiège) A Super-Jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406Tsapras, Y.; Choi, J.-Y.; Street, R. A. et alin Astrophysical Journal (2014), 782We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve ... [more ▼]We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a $2.73\pm 0.43\ M_{\rm J}$ planet orbiting a $0.44\pm 0.07\ M_{\odot}$ early M-type star. The distance to the lens is $4.97\pm 0.29$\ kpc and the projected separation between the host star and its planet at the time of the event is $3.45\pm 0.26$ AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens. [less ▲]Detailed reference viewed: 96 (4 ULiège) Companion search around β Pictoris with the newly commissioned L'-band vector vortex coronagraph on VLT/NACOMawet, D.; Absil, Olivier ; Milli, J. et alin Booth, Mark; Matthews, Brenda; Graham, James (Eds.) Exploring the Formation and Evolution of Planetary Systems (2014, January 01)Here we present the installation and successful commissioning of an L'-band Annular Groove Phase Mask (AGPM) coronagraph on VLT/NACO. The AGPM is a vector vortex coronagraph made from diamond ... [more ▼]Here we present the installation and successful commissioning of an L'-band Annular Groove Phase Mask (AGPM) coronagraph on VLT/NACO. The AGPM is a vector vortex coronagraph made from diamond subwavelength gratings tuned to the L' band. The vector vortex coronagraph enables high contrast imaging at very small inner working angle (here 0''.09, the diffraction limit of the VLT at L'), potentially being the key to a new parameter space. During technical and science verification runs, we discovered a late-type companion at two beamwidths from an F0V star (Mawet et al. 2013), and imaged the inner regions of β Pictoris down to the previously unexplored projected radius of 1.75 AU. The circumstellar disk was also resolved from ~= 1'' to 5'' (see J. Milli et al., these proceedings). These results showcase the potential of the NACO L-band AGPM over a wide range of spatial scales. [less ▲]Detailed reference viewed: 42 (9 ULiège) X-ray AGN in the XMM-LSS galaxy clusters: No evidence of AGN suppressionKoulouridis, E.; Plionis, M.; Melnyk, O. et alin Astronomy and Astrophysics (2014), 567We present a study of the overdensity of X-ray-selected active galactic nuclei (AGN) in 33 galaxy clusters in the XMM-LSS field (The XMM-Newton Large Scale Structure Survey), up to redshift z = 1.05 and ... [more ▼]We present a study of the overdensity of X-ray-selected active galactic nuclei (AGN) in 33 galaxy clusters in the XMM-LSS field (The XMM-Newton Large Scale Structure Survey), up to redshift z = 1.05 and further divided into a lower (0.14 ≤ z ≤ 0.35) and a higher redshift (0.43 ≤ z ≤ 1.05) subsample. Previous studies have shown that the presence of X-ray-selected AGN in rich galaxy clusters is suppressed, since their number is significantly lower than what is expected from the high galaxy overdensities in the area. In the current study we have investigated the occurrence of X-ray-selected AGN in low ( = 2.7 - 1043 erg/s) and moderate ( = 2.4 × 1044 erg/s) X-ray luminosity galaxy clusters in an attempt to trace back the relation between high-density environments and nuclear activity. Owing to the wide contiguous XMM-LSS survey area, we were able to extend the study to the cluster outskirts. We therefore determined the projected overdensity of X-ray point-like sources around each cluster out to 6r500 radius, within δr500 = 1 annulus, with respect to the field expectations based on the X-ray source log N - log S of the XMM-LSS field. To provide robust statistical results we also conducted a consistent stacking analysis separately for the two z ranges. We investigated whether the observed X-ray overdensities are to be expected thanks to the obvious enhancement of galaxy numbers in the cluster environment by also estimating the corresponding optical galaxy overdensities, and we assessed the possible enhancement or suppression of AGN activity in clusters. We find a positive X-ray projected overdensity in both redshift ranges at the first radial bins, which however has the same amplitude as that of optical galaxies. Therefore, no suppression (or enhancement) of X-ray AGN activity with respect to the field is found, in sharp contrast to previous results based on rich galaxy clusters, implying that the mechanisms responsible for the suppression are not as effective in lower density environments. After a drop to roughly the background level between 2 and 3r500, the X-ray overdensity exhibits a rise at larger radii, significantly greater than the corresponding optical overdensity. The radial distance of this overdensity "bump", corresponding to ∼1.5-3 Mpc, depends on the richness of the clusters, as well as on the overall X-ray overdensity profile. Finally, using the redshift information, photometric or spectroscopic, of the optical counterparts, we derive the spatial overdensity profile of the clusters.We find that the agreement between X-ray and optical overdensities in the first radial bins is also suggested in the 3-dimensional analysis. However, we argue that the X-ray overdensity "bump" at larger radial distance is at least partially a result of flux boosting by gravitational lensing of background quasi-stellar objects, confirming previous results. For high-redshift clusters, the enhancement of X-ray AGN activity in their outskirts appears to be intrinsic. We argue that a spatial analysis is crucial for disentangling irrelevant phenomena affecting the projected analysis, but we are still not able to report statistically significant results on the spatial overdensity of AGN in clusters or their outskirts because we lack the necessary numbers. © ESO 2014. [less ▲]Detailed reference viewed: 15 (0 ULiège) High-precision photometry by telescope defocussing - VI. WASP-24, WASP-25 andWASP-26*Southworth, J.; Hinse, T. C.; Burgdorf, M. et alin Monthly Notices of the Royal Astronomical Society (2014), 444(1), 776-789We present time series photometric observations of 13 transits in the planetary systems WASP-24, WASP-25 and WASP-26. All three systems have orbital obliquity measurements, WASP-24 andWASP-26 have been ... [more ▼]We present time series photometric observations of 13 transits in the planetary systems WASP-24, WASP-25 and WASP-26. All three systems have orbital obliquity measurements, WASP-24 andWASP-26 have been observed with Spitzer, andWASP-25 was previously comparatively neglected. Our light curves were obtained using the telescope-defocussing method and have scatters of 0.5-1.2 mmag relative to their best-fitting geometric models. We use these data to measure the physical properties and orbital ephemerides of the systems to high precision, finding that our improved measurements are in good agreement with previous studies. High-resolution Lucky Imaging observations of all three targets show no evidence for faint stars close enough to contaminate our photometry. We confirm the eclipsing nature of the star closest to WASP-24 and present the detection of a detached eclipsing binary within 4.25 arcmin of WASP-26. © 2014 The Authors. [less ▲]Detailed reference viewed: 30 (3 ULiège) High-precision photometry by telescope defocusing - VII. The ultrashort period planet WASP-103Southworth, J.; Mancini, L.; Ciceri, S. et alin Monthly Notices of the Royal Astronomical Society (2014), 447(1), 711-721We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision ... [more ▼]We present 17 transit light curves of the ultrashort period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision reference epoch for transit timing studies. The time of the reference transit mid-point is now measured to an accuracy of 4.8 s, versus 67.4 s in the discovery paper, aiding future searches for orbital decay. With the help of published spectroscopic measurements and theoretical stellar models, we determine the physical properties of the system to high precision and present a detailed error budget for these calculations. The planet has a Roche lobe filling factor of 0.58, leading to a significant asphericity; we correct its measured mass and mean density for this phenomenon. A high-resolution Lucky Imaging observation shows no evidence for faint stars close enough to contaminate the point spread function of WASP-103. Our data were obtained in the Bessell RI and the SDSS griz passbands and yield a larger planet radius at bluer optical wavelengths, to a confidence level of 7.3σ. Interpreting this as an effect of Rayleigh scattering in the planetary atmosphere leads to a measurement of the planetary mass which is too small by a factor of 5, implying that Rayleigh scattering is not the main cause of the variation of radius with wavelength. © 2014 The Authors. [less ▲]Detailed reference viewed: 30 (1 ULiège) Asymptotic solutions for the case of SIE lens models and application to the quadruply imaged quasar Q2237+0305Wertz, Olivier ; Surdej, Jean in Monthly Notices of the Royal Astronomical Society (2014), 442(1), 428-439Considering a small misalignment between a point-like source, a singular isothermal ellipsoid deflector and an observer, we derive to first order simple relations between the model parameters and the ... [more ▼]Considering a small misalignment between a point-like source, a singular isothermal ellipsoid deflector and an observer, we derive to first order simple relations between the model parameters and the lensed image positions, and an expression for the time delay between pairs of opposed images which is analogue to the one previously derived for the case of ε - γ models. Combined with the first-order astrometric relations, we retrieve a simple expression for the time delays, in agreement with Witt, Mao & Keeton, which solely depends on the lensed image positions. The real advantage of using the first-order equations when dealing with symmetric gravitational lens systems is to directly test the validity of the adopted lens model without having to perform any accurate numerical fit. In this paper, we present in detail the calculations which lead to those relations between the singular isothermal ellipsoid lens model parameters and the lensed image positions. In addition, we model the well-known Einstein cross Q2237+0305 with three families of models: ε - γ, singular isothermal ellipsoid and non-singular isothermal ellipsoid plus shear, using a genetic algorithm from the Qubist Optimization Toolbox. We conclude that although the non-singular isothermal ellipsoid plus shear model shows the best agreement between the calculated and the observed image positions (〈 Δx〉 = 0.0026 arcsec), the more simple singular isothermal ellipsoid also leads to quite satisfactory and acceptable results (〈 Δx〉 = 0.0059 arcsec). © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]Detailed reference viewed: 17 (3 ULiège) Physical properties of the WASP-67 planetary system from multi-colour photometryMancini, L.; Southworth, J.; Ciceri, S. et alin Astronomy and Astrophysics (2014), 568Context. The extrasolar planet WASP-67 b is the first hot Jupiter definitively known to undergo only partial eclipses. The lack of the second and third contact points in this planetary system makes it ... [more ▼]Context. The extrasolar planet WASP-67 b is the first hot Jupiter definitively known to undergo only partial eclipses. The lack of the second and third contact points in this planetary system makes it difficult to obtain accurate measurements of its physical parameters. [less ▲]Detailed reference viewed: 20 (1 ULiège) Planet Formation Imager (PFI): Introduction and technical considerationsMonnier, J. D.; Kraus, S.; Buscher, D. et alin Proceedings of SPIE - The International Society for Optical Engineering (2014), 9146Complex non-linear and dynamic processes lie at the heart of the planet formation process. Through numerical simulation and basic observational constraints, the basics of planet formation are now coming ... [more ▼]Complex non-linear and dynamic processes lie at the heart of the planet formation process. Through numerical simulation and basic observational constraints, the basics of planet formation are now coming into focus. High resolution imaging at a range of wavelengths will give us a glimpse into the past of our own solar system and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions. Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals and from here we launch our planning efforts. The aim of the "Planet Formation Imager" (PFI) project is to develop the roadmap for the construction of a new near-/mid-infrared interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. PFI will be able to detect the emission of the cooling, newlyformed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Here we introduce the Planet Formation Imager (PFI) Project (www.planetformationimager.org) and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements. © 2014 SPIE. [less ▲]Detailed reference viewed: 7 (2 ULiège)