Showing results 21 to 24 of 24
  Deconvolution of HST images of the Cloverleaf gravitational lens - Detection of the lensing galaxy and a partial Einstein ringChantry, Virginie  ; Magain, Pierre in Astronomy and Astrophysics (2007), 470(2), 467-473 Archival HST/NICMOS-2 images of the Cloverleaf gravitational lens ( H1413+ 117), a quadruply-imaged quasar, were analysed with a new method derived from the MCS deconvolution algorithm (Magain et al. 1998 ... [more ▼] Archival HST/NICMOS-2 images of the Cloverleaf gravitational lens ( H1413+ 117), a quadruply-imaged quasar, were analysed with a new method derived from the MCS deconvolution algorithm (Magain et al. 1998). This method is based on an iterative process which simultaneously allows us to determine the Point Spread Function ( PSF) and to perform a deconvolution of images containing several point sources plus extended structures. As such, it is well-adapted to the processing of gravitational lens images, especially in the case of multiply-imaged quasars. Two sets of data were analysed: the first one, which was obtained through the F160W filter in 1997, basically corresponds to a continuum image, while the second one, obtained through the narrower F180M filter in 2003, is centered around the forbidden [OIII] emission lines at the source redshift, thus probing the narrow-line region of the quasar. The deconvolution gives astrometric and photometric measurements in both filters and reveals the primary lensing galaxy as well as a partial Einstein ring. The high accuracy of the results is particularly important in order to model the lensing system and to reconstruct the source undergoing the strong lensing. The reliability of the method is checked on a synthetic image similar to H1413+117. [less ▲] Detailed reference viewed: 39 (11 ULg)High precision photometry in crowded stellar fieldsMagain, Pierre ; ; Gillon, Michaël et alin SPIE Newsroom (2006) A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for ... [more ▼] A deconvolution-based method which allows to derive high-precision photometry of stars in crowded fields, proves very useful for a variety of astronomical projects, including transit searches for extrasolar planets. [less ▲] Detailed reference viewed: 20 (3 ULg)Effets de la composition chimique sur les oscillations des étoiles de type $\beta$ Cephei: application au cas de EN (16) Lacertae.Chantry, Virginie Master's dissertation (2004) Detailed reference viewed: 9 (0 ULg) Evolution of the Io footprint brightness I: Far-UV observationsBonfond, Bertrand ; ; Gérard, Jean-Claude et alin Planetary and Space Science (n.d.) The Io footprint (IFP) is a set of auroral spots and an extended tail resulting from the strong interaction between Io and the Jovian magnetosphere. For the first time, we present measurements of the ... [more ▼] The Io footprint (IFP) is a set of auroral spots and an extended tail resulting from the strong interaction between Io and the Jovian magnetosphere. For the first time, we present measurements of the brightness and precipitated power for each individual spot, using the image database gathered from 1997 to 2009 with the Hubble Space Telescope in the Far-UV domain. We show that the relative brightness of the spots varies with the System III longitude, which is a further indication that they originate from different processes. Moreover, our novel measurement method based on 3D simulations of the auroral features allows to derive the precipitated energy fluxes from images on which the emission region is observed at a slant angle. Peak values as high as 2000 mW/m2 are observed for the main spot, probably triggering a localized and sudden heating of the atmosphere. Additionally, strong brightness differences are observed from one hemisphere to another. This result indicates that the location of Io in the plasma torus is not the only parameter to control the brightness, but that the magnetic field asymmetries also play a key role. Finally, we present new data confirming that significant variations of the spots’ brightness on timescales of 2-4 minutes are ubiquitous, which suggests a relationship with intermittent double layers close to Jovian surface. [less ▲] Detailed reference viewed: 15 (6 ULg)
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