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See detailA brown dwarf orbiting an M-dwarf: MOA 2009-BLG-411L
Bachelet, E.; Fouqué, P.; Han, C. et al

in Astronomy and Astrophysics (2012), 547

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the ... [more ▼]

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the companion signal to be extracted. <BR /> Aims: MOA 2009-BLG-411 was detected on August 5, 2009 by the MOA-Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. <BR /> Methods: Thanks to observations by all the collaborations, this event was well monitored. We first decided to characterize the source star properties by using a more refined method than the classical one: we measure the interstellar absorption along the line of sight in five different passbands (VIJHK). Secondly, we model the lightcurve by using the standard technique: make (s,q,α) grids to look for local minima and refine the results by using a downhill method (Markov chain Monte Carlo). Finally, we use a Galactic model to estimate the physical properties of the lens components. <BR /> Results: We find that the source star is a giant G star with radius 9 R[SUB]&sun;[/SUB]. The grid search gives two local minima, which correspond to the theoretical degeneracy s ≡ s[SUP]-1[/SUP]. We find that the lens is composed of a brown dwarf secondary of mass M[SUB]S[/SUB] = 0.05 M[SUB]&sun;[/SUB] orbiting a primary M-star of mass M[SUB]P[/SUB] = 0.18 M[SUB]&sun;[/SUB]. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries. <BR /> Conclusions: As far as we are aware, this is the first detection using the microlensing technique of a binary system in our Galaxy composed of an M-star and a brown dwarf. Appendix is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailPlein de Soleils … à nos pieds
Surdej, Jean ULg

Learning material (2012)

Expérience: En nous promenant sous des feuillages en automne, au printemps ou en été, on peut apercevoir sur le sol plein de petits disques elliptiques plus ou moins lumineux qui ne sont rien d’autres que ... [more ▼]

Expérience: En nous promenant sous des feuillages en automne, au printemps ou en été, on peut apercevoir sur le sol plein de petits disques elliptiques plus ou moins lumineux qui ne sont rien d’autres que des images fidèles du Soleil projetées au travers de minuscules trous présents dans les feuillages des arbres ... [less ▲]

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See detailTélescope à miroir liquide: Astrophysique et Techniques Spatiales: Cours No 8/ Ingés aéro/Ingés phys, Cours No 5/Phys Master en Sciences Spatiales 2011-2012 (Fichiers pdf + vidéos:mov, m4v)
Surdej, Jean ULg

Learning material (2011)

Description du projet international de construction d'un télescope à miroir liquide de 4M de diamètre (ILMT)

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See detailDiscovery and Mass Measurements of a Cold, 10 Earth Mass Planet and Its Host Star
Muraki, Y.; Han, C.; Bennett, D. P. et al

in Astrophysical Journal (2011), 741

We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, performed with the gravitational microlensing method. This planet has a mass of m[SUB]p[/SUB] = 10.4 ± 1.7 M ... [more ▼]

We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, performed with the gravitational microlensing method. This planet has a mass of m[SUB]p[/SUB] = 10.4 ± 1.7 M[SUB]⊕[/SUB] and orbits a star of mass M [SUB]sstarf[/SUB] = 0.56 ± 0.09 M[SUB]sun[/SUB] at a semimajor axis of a = 3.2{+1.9\atop -0.5} AU and an orbital period of P = 7.6{+7.7\atop -1.5} yrs. The planet and host star mass measurements are enabled by the measurement of the microlensing parallax effect, which is seen primarily in the light curve distortion due to the orbital motion of the Earth. But the analysis also demonstrates the capability to measure the microlensing parallax with the Deep Impact (or EPOXI) spacecraft in a heliocentric orbit. The planet mass and orbital distance are similar to predictions for the critical core mass needed to accrete a substantial gaseous envelope, and thus may indicate that this planet is a "failed" gas giant. This and future microlensing detections will test planet formation theory predictions regarding the prevalence and masses of such planets. [less ▲]

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See detailThe XMM-LSS survey: optical assessment and properties of different X-ray selected cluster classes
Adami, C.; Mazure, A.; Pierre, M. et al

in Astronomy and Astrophysics (2011), 526(A18), 36

XMM and Chandra opened a new area for the study of clusters of galaxies. Not only for cluster physics but also, for the detection of faint and distant clusters that were inaccessible with previous ... [more ▼]

XMM and Chandra opened a new area for the study of clusters of galaxies. Not only for cluster physics but also, for the detection of faint and distant clusters that were inaccessible with previous missions. This article presents 66 spectroscopically confirmed clusters (0.05<z<1.5) within an area of 6 deg2 enclosed in the XMM-LSS survey. Almost two thirds have been confirmed with dedicated spectroscopy only and 10% have been confirmed with dedicated spectroscopy supplemented by literature redshifts. Sub-samples, or classes, of extended-sources are defined in a two-dimensional X-ray parameter space allowing for various degrees of completeness and contamination. We describe the procedure developed to assess the reality of these cluster candidates using the CFHTLS photometric data and spectroscopic information from our own follow-up campaigns. Most of these objects are low mass clusters, hence constituting a still poorly studied population. In a second step, we quantify correlations between the optical properties such as richness or velocity dispersion and the cluster X-ray luminosities. We examine the relation of the clusters to the cosmic web. Finally, we review peculiar structures in the surveyed area like very distant clusters and fossil groups. [less ▲]

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See detailLentilles gravitationnelles, Cours No 3: Astrophysique et Techniques Spatiales: Ingés aéro/Ingés Phys 2011-2012 (Fichiers pdf + vidéos: mov, avi, m4v)
Surdej, Jean ULg

Learning material (2011)

Introduction à la théorie des lentilles gravitationnelles (3ème partie)

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See detailLentilles gravitationnelles, Cours No 2: Astrophysique et Techniques Spatiales: Ingés aéro/ Ingés Phys 2011-2012 (Fichier PDF + vidéos: mov, avi, m4v)
Surdej, Jean ULg

Learning material (2011)

Introduction à la théorie des lentilles gravitationnelles (2ème partie)

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See detailLentilles gravitationnelles, Cours No 1: Astrophysique et Techniques Spatiales: Ingés aéro/ Ingés Phys 2011-2012 (Fichier PDF + vidéos: mov, m4v)
Surdej, Jean ULg

Learning material (2011)

Introduction à la théorie des lentilles gravitationnelles (1ère partie)

Detailed reference viewed: 517 (85 ULg)