Daniel Rouan

Performance of the Canada-France-Hawaii Telescope Adaptive Optics Bonnette

ABSTRACT Extensive results from the commissioning phase of PUEO, the adaptive optics instrument adaptor for the Canada‐France‐Hawaii Telescope (CFHT), are presented and discussed. Analyses of more than 750 images recorded with a CCD and a near‐IR camera on 16 nights in wavelengths from B to H are used to derive the properties of the compensated wavefront and images in a variety of conditions. The performance characteristics of the system are analyzed and presented in several ways, in terms of delivered Strehl ratios, full width half‐maxima (FWHM), and quantities describing the improvements of both. A qualitative description is given of how the properties of the corrected images result from the structure function of the compensated phase. Under median seeing conditions, PUEO delivers essentially diffraction‐limited images at H and K and images with FWHM ∼ 0 documentclass{aastex} usepackage{amsbsy} usepackage{amsfonts} usepackage{amssymb} usepackage{bm} usepackage{mathrsfs} usepackage{pifont} usepac...

Transiting exoplanets from the CoRoT space mission IX. CoRoT-6b: a transiting 'hot Jupiter' planet in an 8.9d orbit around a low-metallicity star ?

The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations ‐ photometric and spectroscopic ‐ carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a ‘hot Jupiter’ planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high 7 Li abundance. While the light curve indicates a much higher level of activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Caii] H&K lines.

Transiting exoplanets from the CoRoT space mission - V. CoRoT-Exo-4b: stellar and planetary parameters

Aims. The CoRoT satellite has announced its fourth transiting planet (Aigrain et al. 2008, A&A, 488, L43) with space photometry. We describe and analyse complementary observations of this system performed to establish the planetary nature of the transiting body and to estimate the fundamental parameters of the planet and its parent star. Methods. We have analysed high precision radial-velocity data, ground-based photometry, and high signal-to-noise ratio spectroscopy.

Hot Very Small dust Grains in NGC 1068 seen in jet induced structures thanks to VLT/NACO adaptive optics

We present K, L and M diffraction-limited images of NGC 1068 obtained with NAOS+CONICA at VLT/YEPUN over a 3.5 field around the central engine. Hot dust (Tcol = 550-650 K) is found in three different regions : (a) in the true nucleus, seen as a slightly NS elongated, core of extremely hot dust, resolved in K and L with respective diameters of ~5 pc and 8.5 pc ; (b) along the NS direction, as a spiral arm and a southern tongue ; (c) as a set of parallel elongatednodules (wave-like) bracketting the jet. Several structures observed on radio maps, mid-IR or HST UV-visible maps are seen, so that a precise registration can be done from UV to 6 cm. These results dosupport the current interpretion that source (a) corresponds to emission from dust near sublimation temperature delimiting the walls of the cavity in the central obscuring torus. Structure (b) is thought tobe a mixture of hot dust and active star forming regions along a micro spiral structure that could trace the tidal mechanism bringing matter to the central engine. Structure c)which was not known, exhibits too high a temperature for classical grains ; it is most probably the signature of transiently heated very small dust grains (VSG) : nano-diamonds, whichare resistant and can form in strong UV field or in shocks, are very attractive candidates. The waves can be condensations triggered by jet induced shocks, as predicted by recent models. First estimates, based on a simple VSG model and on a detailed radiative transfer model, do agree with those interpretations,both qualitatively and quantitatively.

The SARS algorithm: detrending CoRoT light curves with Sysrem using simultaneous external parameters

Surveys for exoplanetary transits are usually limited not by photon noise but rather by the amount of red noise in their data. In particular, although the CoRoT space-based survey data are being carefully scrutinized, significant new sources of systematic noises are still being discovered. Recently, a magnitude-dependant systematic effect was discovered in the CoRoT data by Mazeh et al. and a phenomenological correction was proposed. Here we tie the observed effect to a particular type of effect, and in the process generalize the popular Sysrem algorithm to include external parameters in a simultaneous solution with the unknown effects. We show that a post-processing scheme based on this algorithm performs well and indeed allows for the detection of new transit-like signals that were not previously detected.

VLT/NACO infrared adaptive optics images of small scale structures in OMC1 ⋆

Near-infrared observations of line emission from excited H 2 and in the continuum are reported in the direction of the Orion molecular cloud OMC1 , using the European Southern Observatory Very Large Telescope UT4 , equipped with the NAOS adaptive optics system on the CONICA infrared array camera. Spatial resolution has been achieved at close to the diffraction limit of the telescope (0. 08 −0. 12) and images show a wealth of morphological detail. Structure is not fractal but shows two preferred scale sizes of 2. (1100 AU) and 1. 2 (540 AU) , where the larger scale may be associated with star formation. Key words. ISM : individual objects : OMC1 – ISM : circumstellar matter – ISM : kinematics and dynamics – ISM : molecules – infrared : ISM

Polarimetric imaging of NGC 1068 at high angular resolution in the near infrared - Direct evidence of an extended nuclear torus

Aims. One of the main observational challenges for investigating the central regions of active galactic nuclei (AGN) at short wavelengths, using high angular resolution, and high contrast observations, is to directly detect the circumnuclear optically thick material hiding the central core emission when viewed edge-on. The lack of direct evidence is limiting our understanding of AGN, and several scenarios have been proposed to cope for the diverse observed aspects of activity in a unified approach. Methods. Observations in the near-infrared spectral range have shown themselves to be powerful for providing essential hints to the characterisation of the unified model ingredients because of the reduced optical depth of the obscuring material. Moreover, it is possible to trace this material through light scattered from the central engine’s closest environment, so that polarimetric observations are the ideal tool for distinguishing it from purely thermal and stellar emissions. Results. Here we show strong evidence that there is an extended nuclear torus at the center of NGC 1068 thanks to new adaptiveoptics-assisted polarimetric observations in the near-infrared. The orientation of the polarization vectors proves that there is a structured hourglass-shaped bicone and a compact elongated (20 × 60 pc) nuclear structure perpendicular to the bicone axis. The linearly polarized emission in the bicone is dominated by a centro-symmetric pattern, but the central compact region shows a clear deviation from the latter with linear polarization aligned perpendicular to the bicone axis.

Exoplanet Discoveries with the CoRoT Space Observatory

The CoRoT space observatory is a project which is led by the French space agency CNES and leading space research institutes in Austria, Brazil, Belgium, Germany and Spain and also the European Space Agency ESA. CoRoT observed since its launch in December 27, 2006 about 100 000 stars for the exoplanet channel, during 150 days uninterrupted high-precision photometry. Since the The CoRoT-team has several exoplanet candidates which are currently analyzed under its study, we report here the discoveries of nine exoplanets which were observed by CoRoT. Discovered exoplanets such as CoRoT-3b populate the brown dwarf desert and close the gap of measured physical properties between usual gas giants and very low mass stars. CoRoT discoveries extended the known range of planet masses down to about 4.8 Earth-masses (CoRoT-7b) and up to 21 Jupiter masses (CoRoT-3b), the radii to about 1.68 × 0.09 REarth (CoRoT-7b) and up to the most inflated hot Jupiter with 1.49 × 0.09 REarth found so far (CoRoT-1b), and the transiting exoplanet with the longest period of 95.274 days (CoRoT-9b). Giant exoplanets have been detected at low metallicity, rapidly rotating and active, spotted stars. Two CoRoT planets have host stars with the lowest content of heavy elements known to show a transit hinting towards a different planethost-star-metallicity relation then the one found by radial-velocity search programs. Finally the properties of the CoRoT-7b prove that rocky planets with a density close to Earth exist outside the Solar System. Finally the detection of the secondary transit of CoRoT-1b at a sensitivity level of 10−5 and the very clear detection of the “super-Earth” CoRoT-7b at 3.5 × 10−4 relative flux are promising evidence that the space observatory is being able to detect even smaller exoplanets with the size of the Earth.

Science Case and Requirements for the MOSAIC Concept for a Multi-Object Spectrograph for the European Extremely Large Telescope

Over the past 18 months we have revisited the science requirements for a multi-object spectrograph (MOS) for the European Extremely Large Telescope (E-ELT). These efforts span the full range of E-ELT science and include input from a broad cross-section of astronomers across the ESO partner countries. In this contribution we summarise the key cases relating to studies of high-redshift galaxies, galaxy evolution, and stellar populations, with a more expansive presentation of a new case relating to detection of exoplanets in stellar clusters. A general requirement is the need for two observational modes to best exploit the large (≥40 arcmin2) patrol field of the E-ELT. The first mode (‘high multiplex’) requires integrated-light (or coarsely resolved) optical/near-IR spectroscopy of >100 objects simultaneously. The second (‘high definition’), enabled by wide-field adaptive optics, requires spatially-resolved, near-IR of >10 objects/sub-fields. Within the context of the conceptual study for an ELT-MOS called MOSAIC, we summarise the toplevel requirements from each case and introduce the next steps in the design process.

A new concept of achromatic phase shifter for nulling interferometry

Direct detection and characterization of a planet around a star by nulling interferometry, must be efficient in a large wavelength domain in order to detect simultaneously the infrared bio-tracers CO2, O3 and H2O. This condition requires that an achromatic phase shift of π be implemented, with an accuracy sufficient for achieving a deep nulling at all considered wavelengths. Several solutions have been presented. We present here a new concept for designing such an achromatic phase shifter. It is based on two cellular mirrors (alternatively, transparent plates can be used) where cells have thickness which are respectively odd and even multiples of a quarter of the central wavelength. Each cell introduces then a phase shift of (2k + 1)π or of 2kπ, on the fraction of the wave it reflects. Each mirror is introduced in the collimated beam issued from one or the other telescopes. Because of the odd/even distribution, a destructive interference is obviously produced on axis for the central wavelength when recombining the two beams. The trick to obtain a quasi-achromatisation is to distribute the thickness of the cells, so that the nulling is also efficient for a wavelength not too far from the central wavelength. We show that if the thicknesses are distributed according to the Pascal triangle, a fair quasi-achromatism is reached. This effect is the more efficient that the number of cells is large. For instance, with 256 × 256 cells, where phase shift range is between -6π and +6π one shows that the nulling reaches 10-6 on the wavelength range [0.7λ0, 1.3λ0] which corresponds roughly to the DARWIN specification. In a second step, we study the optimum way to distribute the cells in the plane of the pupil. The most important criterion is the isolation of the planet image from the residual image of the star. Several efficient configurations are presented. Finally we consider some practical aspects on a device belonging to the real world and on the bench we are developing. The major interest of this solution is that it allows a compact, simple and fully symmetric design, with essentially no ajustable sub-systems ; extension to multi-telescopes interferometers with phase shift other than π can also be envisioned.