References of "Surdej, Jean"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailLarger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration
Southworth, John; Mancini, L.; Tregloan-Reed, J. et al

in Monthly Notices of the Royal Astronomical Society (2015), 454

Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 ... [more ▼]

Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5 s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the subsolar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet's radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets. [less ▲]

Detailed reference viewed: 29 (1 ULiège)
Full Text
See detailPerformance evaluation of mid-IR vortex coronagraphs with centrally obscured segmented pupils
Carlomagno, Brunella ULiege; Absil, Olivier ULiege; Ruane, Garreth J. et al

Poster (2015, October)

In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L ... [more ▼]

In its original design, the E-ELT/Metis instrument envisages a vortex coronagraph in the mid-IR regime for detection and characterization of exoplanets, with a contrast of 1e-4 at 2 lambda/D (~40 mas in L band). The AGPM (Annular Groove Phase Mask) is a vortex phase mask with impressive characteristics: small inner working angle, high throughput, achromaticity. A non-perfectly circular pupil and non-flat input wavefront result in a starlight leakage, degrading the performance of the vortex coronagraph. In this work, we present end-to-end performance simulations using Fourier optical propagation to determine the quality of the starlight rejection obtained with an infrared vortex coronagraph. We first analyse the performance facing E-ELT pupil variations (segmentations, central obscuration, spiders, missing segments), then pointing jitter and random adaptive optics residual phase screens are introduced to derive more realistic performance. Finally, more advanced concepts of the infrared vortex coronagraph are presented, in order to compensate for performance degradation. [less ▲]

Detailed reference viewed: 31 (5 ULiège)
Full Text
See detailCours No 1: Astrophysique et Techniques Spatiales: Ingés aéro/ Ingés Phys 2015-2016 (Fichier PDF + vidéos: mov)
Surdej, Jean ULiege

Learning material (2015)

Dans la première partie du cours consacré à l'astrophysique galactique, nous étudierons les propriétés globales des astres (luminosités, couleurs, distances, masses, rayons). Dans la seconde partie, nous ... [more ▼]

Dans la première partie du cours consacré à l'astrophysique galactique, nous étudierons les propriétés globales des astres (luminosités, couleurs, distances, masses, rayons). Dans la seconde partie, nous aborderons l'étude des astres extragalactiques. Enfin, la troisième partie du cours sera consacrée à la compréhension des instruments et télescopes modernes utilisés tant au sol que dans l'espace. [less ▲]

Detailed reference viewed: 99 (18 ULiège)
Full Text
See detailA Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency
Piron, Pierre ULiege; Delacroix, Christian; Huby, Elsa ULiege et al

in Shaklan, Stuart (Ed.) Techniques and Instrumentation for Detection of Exoplanets VII (2015, September 11)

The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a ... [more ▼]

The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a telescope element provides a continuous helical phase ramp for an on axis sources, which creates the orbital angular momentum. Thanks to that phase, the intensity of the central source is canceled by a down-stream pupil stop, while the off axis sources are not affected. However due to experimental conditions the nulling is hardly perfect. To improve the null, a Mach-Zehnder interferometer containing Dove prisms differently oriented can be proposed to sort out light based on its orbital angular momentum (OAM). Thanks to the differential rotation of the beam, a π phase shift is achieved for the on axis light affected by a non zero OAM. Therefore the contrast between the star and its faint companion is enhanced. Nevertheless, due the Dove prisms birefringence, the performance of the interferometer is relatively poor. To solve this problem, we propose to add a birefringent wave-plate in each arm to compensate this birefringence. In this paper, we will develop the mathematical model of the wave front using the Jones formalism. The performance of the interferometer is at first computed for the simple version without the birefringent plate. Then the effect of the birefringent plate is be mathematically described and the performance is re-computed. [less ▲]

Detailed reference viewed: 42 (11 ULiège)
See detailThe 4m International Liquid Mirror Telescope
Surdej, Jean ULiege

Conference (2015, September 07)

The International Liquid Mirror Telescope (ILMT) consists of a 4-m diameter zenith telescope with a liquid mirror characterized by a f/2 focal ratio. It is a collaborative project between Belgium, Canada ... [more ▼]

The International Liquid Mirror Telescope (ILMT) consists of a 4-m diameter zenith telescope with a liquid mirror characterized by a f/2 focal ratio. It is a collaborative project between Belgium, Canada, India and Poland. The participating institutions are: Institute of Astrophysics and Geophysics of the Liege University (IAGL), the Royal Observatory of Belgium (ROB), six Canadian universities (British Columbia, Laval, Montreal, Toronto, Victoria and York), the Aryabatta Research Institute of Observational Sciences (ARIES, Nainital, India) and the Observatory of Poznan (UAM, Poland). This telescope is being installed at the Devasthal observatory, India (Longitude 79° 41' 04'' E, +29° 21' 40'' N, altitude 2450m), in the central Himalayas. First light should happen in early 2016. It will image every night a strip of sky having an approximate width of 27' in declination using a 4096 x 4096 pixel CCD detector that will work in the time delay integration (TDI) mode. The ILMT will thus perform a deep survey of a long and narrow strip of sky by looking at stars, galaxies, AGN, quasars, asteroids, space debris, ... crossing its field of view. It will observe in the i', r', g' SDSS spectral bands. This survey will thus be mainly dedicated to photometric and astrometric variability studies of faint objects. Among the main scientific goals, let us mention the detection and follow up of a few tens of multiply imaged quasars produced by gravitational lensing, hundreds of supernovae every year, detection of nearby brown dwarfs, white dwarfs and other faint stars based upon their trigonometric parallax and/or proper motion measurements, photometric variability studies of thousands of quasars and millions of stars as well as space debris detection at dusk and/or at dawn. Right now, numerous data sets have already been obtained of the ILMT strip of sky with smaller telescopes in the TDI mode. These will be used to carry out preliminary scientific projects and calibration of the ILMT data. A pipeline and database are presently in construction at the Poznan Observatory. Some videos and recent photographs will illustrate the present status of the ILMT project. [less ▲]

Detailed reference viewed: 43 (9 ULiège)
Full Text
See detailDirect exoplanet imaging with small-angle Vortex coronagraphs
Defrere, Denis ULiege; Absil, Olivier ULiege; Mawet, D. et al

Conference (2015, July 16)

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They enhance the dynamic range at very small inner working angle ... [more ▼]

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They enhance the dynamic range at very small inner working angle (down to the diffraction limit of the telescope) and provide a clear 360 degree discovery space for high-contrast direct imaging of exoplanets. In this talk, we will report on the first scientific results obtained with Vortex coronagraphs installed on 10-m class telescopes (i.e., the VLT and the LBT) and on the recent installation of one Vortex at Keck. We will describe the in-lab and on-sky performance of the Vortex, and describe the lessons learned after a few years of operation. Finally, we will discuss the prospects of our vortices for future extremely large telescopes and space missions. [less ▲]

Detailed reference viewed: 23 (3 ULiège)
Full Text
Peer Reviewed
See detailSingle Wavelength Coarse Phasing In Segmented Telescopes
Simar, Juan Felipe ULiege; Stockman, Yvan ULiege; Surdej, Jean ULiege

in Applied Optics (2015), 54

Space observations of fainter and more distant astronomical objects constantly require telescope primary mirrors with a larger size. The diameter of monolithic primary mirrors is limited to 10 m because ... [more ▼]

Space observations of fainter and more distant astronomical objects constantly require telescope primary mirrors with a larger size. The diameter of monolithic primary mirrors is limited to 10 m because of manufacturing limitations. For space telescopes, the primary mirrors are limited to less than 5 m due to fairing capacity. Segmented primary mirrors thus constitute an alternative solution to deal with the steadily increase of the primary mirror size. The optical path di erence between the individual segments must be close to zero (few nm) in order to be di raction limited. We propose in this paper a new inter-segment piston sensor based on coherence measurement of a star image. This sensor is intended to be used in the co-phasing system of future segmented mirrors. [less ▲]

Detailed reference viewed: 98 (59 ULiège)
Full Text
Peer Reviewed
See detailSearching for variable stars in the cores of five metal-rich globular clusters using EMCCD observations
Skottfelt, J.; Bramich, D. M.; Figuera Jaimes, R. et al

in Astronomy and Astrophysics (2015), 573

Aims. In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal-rich ([Fe/H] > -1) globular clusters: NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652. The ... [more ▼]

Aims. In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal-rich ([Fe/H] > -1) globular clusters: NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652. The data have been used to perform a census of the variable stars in the central parts of these clusters. Methods. The observations were made with the electron-multiplying charge-couple device (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile, and they were analysed using difference image analysis to obtain high-precision light curves of the variable stars. Results. It was possible to identify and classify all of the previously known or suspected variable stars in the central regions of the five clusters. Furthermore, we were able to identify and, in most cases, classify 48, 49, 7, 8, and 2 previously unknown variables in NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652, respectively. Especially interesting is the case of NGC 6441, for which the variable star population of about 150 stars has been thoroughly examined by previous studies, including a Hubble Space Telescope study. In this paper we are able to present 49 new variable stars for this cluster, of which one (possibly two) are RR Lyrae stars, two are W Virginis stars, and the rest are long-period semi-regular or irregular variables on the red giant branch. We have also detected the first double-mode RR Lyrae in the cluster. © ESO 2015. [less ▲]

Detailed reference viewed: 17 (0 ULiège)
Full Text
Peer Reviewed
See detailTransits and starspots in the WASP-6 planetary system
Tregloan-Reed, J.; Southworth, J.; Burgdorf, M. et al

in Monthly Notices of the Royal Astronomical Society (2015), 450(2), 1760-1769

We present updates to PRISM, a photometric transit-starspot model, and GEMC, a hybrid optimization code combining MCMC and a genetic algorithm. We then present high-precision photometry of four transits ... [more ▼]

We present updates to PRISM, a photometric transit-starspot model, and GEMC, a hybrid optimization code combining MCMC and a genetic algorithm. We then present high-precision photometry of four transits in the WASP-6 planetary system, two of which contain a starspot anomaly. All four transits were modelled using PRISM and GEMC, and the physical properties of the system calculated. We find the mass and radius of the host star to be 0.836 ± 0.063 M<inf>⊙</inf> and 0.864 ± 0.024 R<inf>⊙</inf>, respectively. For the planet, we find a mass of 0.485 ± 0.027 M<inf>Jup</inf>, a radius of 1.230 ± 0.035 R<inf>Jup</inf> and a density of 0.244 ± 0.014 ρ<inf>Jup</inf>. These values are consistent with those found in the literature. In the likely hypothesis that the two spot anomalies are caused by the same starspot or starspot complex, we measure the stars rotation period and velocity to be 23.80 ± 0.15 d and 1.78 ± 0.20 km s-1, respectively, at a colatitude of 75.8°. We find that the sky-projected angle between the stellar spin axis and the planetary orbital axis is λ = 7.2° ± 3.7°, indicating axial alignment. Our results are consistent with and more precise than published spectroscopic measurements of the Rossiter-McLaughlin effect. These results suggest that WASP-6 b formed at amuch greater distance from its host star and suffered orbital decay through tidal interactions with the protoplanetary disc. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]

Detailed reference viewed: 11 (0 ULiège)
Full Text
Peer Reviewed
See detailPredicted multiply imaged X-ray AGNs in the XXL survey
Finet, F.; Elyiv, A.; Melnyk, O. et al

in Monthly Notices of the Royal Astronomical Society (2015), 452(2), 1480-1492

We estimate the incidence of multiply imaged active galactic nuclei (AGNs) among the optical counterparts of X-ray selected point-like sources in the XXL field.We also derive the expected statistical ... [more ▼]

We estimate the incidence of multiply imaged active galactic nuclei (AGNs) among the optical counterparts of X-ray selected point-like sources in the XXL field.We also derive the expected statistical properties of this sample, such as the redshift distribution of the lensed sources and of the deflectors that lead to the formation of multiple images, modelling the deflectors using both spherical and ellipsoidal singular isothermal mass distributions. We further assume that the XXL survey sample has the same overall properties as the smaller XMM-COSMOS sample restricted to the same flux limits and taking into account the detection probability of the XXL survey. Among the X-ray sources with a flux in the [0.5-2] keVband larger than 3.0×10-15 erg cm-2 s-1 and with optical counterparts brighter than an r-band magnitude of 25, we expect ~20 multiply imaged sources. Out of these, ~16 should be detected if the search is made among the seeing-limited images of the X-ray AGN optical counterparts and only one of them should be composed of more than two lensed images. Finally, we study the impact of the cosmological model on the expected fraction of lensed sources. © 2015 The Authors. [less ▲]

Detailed reference viewed: 13 (0 ULiège)
Full Text
Peer Reviewed
See detailOGLE-2011-BLG-0265Lb: A jovian microlensing planet orbiting an m dwarf
Skowron, J.; Shin, I.-G.; Udalski, A. et al

in Astrophysical Journal (2015), 804(1),

We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the ... [more ▼]

We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution. High-cadence temporal coverage of the planetary signal, combined with extended observations throughout the event, allows us to accurately model the observed light curve. However, the final microlensing solution remains degenerate, yielding two possible configurations of the planet and the host star. In the case of the preferred solution, the mass of the planet is Mp = 0.9 ± 0.3 MJ, and the planet is orbiting a star with a mass M = 0.22 ± 0.06 M. The second possible configuration (2? away) consists of a planet with Mp = 0.6 ± 0.3 MJ and host star with M = 0.14 ± 0.06 M. The system is located in the Galactic disk 34 kpc toward the Galactic bulge. In both cases, with an orbit size of 1.52.0 AU, the planet is a cold Jupiterlocated well beyond the snow line of the host star. Currently available data make the secure selection of the correct solution difficult, but there are prospects for lifting the degeneracy with additional follow-up observations in the future, when the lens and source star separate. © 2015. The American Astronomical Society. All rights reserved. [less ▲]

Detailed reference viewed: 13 (0 ULiège)