References of "Absil, Olivier"
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See detailImaging the inner regions of debris disks with near-infrared interferometry
Defrère, D.; Absil, Olivier ULg; Augereau, J. C. et al

in EPSC-DPS Joint Meeting 2011 (2011, October 01)

Most debris disks resolved so far show extended structures located at tens to hundreds AU from the host star, and are more analogous to our solar system's dusty Kuiper belt than to the AU-scale zodiacal ... [more ▼]

Most debris disks resolved so far show extended structures located at tens to hundreds AU from the host star, and are more analogous to our solar system's dusty Kuiper belt than to the AU-scale zodiacal disk inside our solar system's asteroid belt. Over the last few years however, a few hot debris disks have been detected around a handful of main sequence stars thanks to the advance of infrared interferometry. The grain populations derived from these observations are quite intriguing, as they point towards very high dust replenishment rates, high cometary activity or major collisional events. In this talk, we review the ongoing efforts to detect bright exozodiacal disks with precision near-infrared interferometry in both hemispheres with CHARA/FLUOR and VLTI/PIONIER. We discuss preliminary statistical trends on the occurrence of bright exozodi around nearby main sequence stars and show how this information could be used to constrain the global architecture and evolution of debris disks. [less ▲]

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See detailHot exozodiacal dust resolved around Vega with IOTA/IONIC
Defrère, D.; Absil, Olivier ULg; Augereau, J.-C. et al

in Astronomy and Astrophysics (2011), 534

Context. Although debris discs have been detected around a significant number of main-sequence stars, only a few of them are known to harbour hot dust in their inner part where terrestrial planets may ... [more ▼]

Context. Although debris discs have been detected around a significant number of main-sequence stars, only a few of them are known to harbour hot dust in their inner part where terrestrial planets may have formed. Thanks to infrared interferometric observations, it is possible to obtain a direct measurement of these regions, which are of prime importance for preparing future exo-Earth characterisation missions. <BR /> Aims: We resolve the exozodiacal dust disc around Vega with the help of infrared stellar interferometry and estimate the integrated H-band flux originating from the first few AUs of the debris disc. <BR /> Methods: Precise H-band interferometric measurements were obtained on Vega with the 3-telescope IOTA/IONIC interferometer (Mount Hopkins, Arizona). Thorough modelling of both interferometric data (squared visibility and closure phase) and spectral energy distribution was performed to constrain the nature of the near-infrared excess emission. <BR /> Results: Resolved circumstellar emission within ~6 AU from Vega is identified at the 3-σ level. The most straightforward scenario consists in a compact dust disc producing a thermal emission that is largely dominated by small grains located between 0.1 and 0.3 AU from Vega and accounting for 1.23 ± 0.45% of the near-infrared stellar flux for our best-fit model. This flux ratio is shown to vary slightly with the geometry of the model used to fit our interferometric data (variations within ± 0.19%). <BR /> Conclusions: The presence of hot exozodiacal dust in the vicinity of Vega, initially revealed by K-band CHARA/FLUOR observations, is confirmed by our H-band IOTA/IONIC measurements. Whereas the origin of the dust is still uncertain, its presence and the possible connection with the outer disc suggest that the Vega system is currently undergoing major dynamical perturbations. [less ▲]

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See detailThe spin-orbit alignment of the Fomalhaut debris disk
Absil, Olivier ULg

Scientific conference (2011, September 30)

The measurement of the Rossiter-MacLaughlin effect in transiting planetary systems has revealed a significant population of hot giant planets orbiting outside the equatorial plane of their parent star. In ... [more ▼]

The measurement of the Rossiter-MacLaughlin effect in transiting planetary systems has revealed a significant population of hot giant planets orbiting outside the equatorial plane of their parent star. In an attempt to improve our understanding of these spin-orbit misalignements, and discriminate between various scenarios, we propose to determine whether debris disks are located within the equatorial plane of their star using infrared spectro-interferometry. To validate our approch, we have chosen the bright star Fomalhaut and measured the orientation of its rotationnally-distorted stellar photosphere using micro-arcsecond precision VLTI/AMBER spectro-astrometry within the Br-gamma line. The derived poition angle is in perfect agreement with the position angle of the cold debris disk imaged in the visible and sub-millimeter domains. We discuss the implications of this result on our understanding of the dust grain properties in the Fomalhaut disk, and how this study can be extended to other debris disk systems. [less ▲]

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See detailTaking the vector vortex coronagraph to the next level for ground- and space-based exoplanet imaging instruments: review of technology developments in the USA, Japan, and Europe
Mawet, Dimitri; Murakami, Naoshi; Delacroix, Christian ULg et al

in Shaklan, Stuart (Ed.) Techniques and Instrumentation for Detection of Exoplanets V. (2011, September 01)

The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground- and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at ... [more ▼]

The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground- and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at Palomar and in the laboratory at JPL, and Hokkaido University. Manufacturing technologies for devices covering wavelength ranges from the optical to the mid-infrared, have been maturing quickly. We will review the current status of technology developments supported by NASA in the USA (Jet Propulsion Laboratory-California Institute of Technology, University of Arizona, JDSU and BEAMCo), Europe (University of Li`ege, Observatoire de Paris- Meudon, University of Uppsala) and Japan (Hokkaido University, and Photonics Lattice Inc.), using liquid crystal polymers, subwavelength gratings, and photonics crystals, respectively. We will then browse concrete perspectives for the use of the VVC on upcoming ground-based facilities with or without (extreme) adaptive optics, extremely large ground-based telescopes, and space-based internal coronagraphs. [less ▲]

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See detailA Dim Candidate Companion to epsilon Cephei
Mawet, D.; Mennesson, B.; Serabyn, E. et al

in Astrophysical Journal Letters (2011), 738

Using a vector vortex coronagraph behind the 1.5 m well-corrected subaperture (WCS) at Palomar, we detected a second object very close to epsilon Cephei, a δ Scuti F0 IV star. The candidate companion, ~50 ... [more ▼]

Using a vector vortex coronagraph behind the 1.5 m well-corrected subaperture (WCS) at Palomar, we detected a second object very close to epsilon Cephei, a δ Scuti F0 IV star. The candidate companion, ~50 times fainter than epsilon Cephei, if physically associated, is a late-type K or early M star, and lies at an angular separation of 330 mas, or 1.1 λ/D for the WCS, making it the smallest angle detection ever realized with a coronagraph in terms of λ/D units. The projected separation of the putative companion is ~8.6 AU, most likely on a highly eccentric orbit. The recently detected near-infrared excess is thus likely not due to hot dust. Moreover, we also show that the previously reported IRAS 60 μm excess was due to source confusion on the galactic plane. [less ▲]

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See detailStudying the Fomalhaut debris disk with infrared interferometry
Absil, Olivier ULg

Scientific conference (2011, July 15)

In this talk, I will describe two recent studies carried out with infrared interferometry to characterise the planetary system around Fomalhaut, and its debris disk in particular. In the first study, we ... [more ▼]

In this talk, I will describe two recent studies carried out with infrared interferometry to characterise the planetary system around Fomalhaut, and its debris disk in particular. In the first study, we aimed to determine whether the debris disk is located within the equatorial plane of the stellar photosphere, in an attempt to improve our understanding of spin-orbit misalignements in planetary systems in general. We measured the orientation of the rotationnally-distorted stellar photosphere using micro-arcsecond precision VLTI/AMBER spectro-astrometry within the Br-gamma line. The derived poition angle is in perfect agreement with the position angle of the cold debris disk measured in visible and sub-millimeter images. We discuss the implications of this result on our understanding of the dust grain properties in the Fomalhaut disk. In the second study, we aimed at characterising the dust content of the innermost part of the debris disk. We used archival high-precision K-band visibility measurements with VLTI/VINCI and obtained N-band nulling observations with the Keck Interferometer Nuller. We report a significant excess emission at K band, and a marginal excess emission at N band, that we attempt to reproduce with a 2D debris disk model. A comprehensive Bayesian analysis of the main disk parameters is performed to derive most-probable values. Our analysis points towards a very compact ring of hot dust close to the sublimation radius as the origin of the reported excess emission. [less ▲]

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See detailOptimized fringe sensors for the VLTI next generation instruments
Blind, N.; Absil, Olivier ULg; Le Bouquin, J.-B. et al

in Astronomy and Astrophysics (2011), 530

Context. With the arrival of the next generation of ground-based imaging interferometers combining from four to possibly six telescopes simultaneously, there is also a strong need for a new generation of ... [more ▼]

Context. With the arrival of the next generation of ground-based imaging interferometers combining from four to possibly six telescopes simultaneously, there is also a strong need for a new generation of fringe trackers able to cophase these arrays. These instruments have to be very sensitive and to provide robust operations in quickly varying observational conditions. <BR /> Aims: We aim at defining the optimal characteristics of fringe sensor concepts operating with four or six telescopes. The current detector limitations lead us to consider solutions based on co-axial pairwise combination schemes. <BR /> Methods: We independently study several aspects of the fringe sensing process: 1) how to measure the phase and the group delay, and 2) how to combine the telescopes to ensure a precise and robust fringe tracking in real conditions. Thanks to analytical developments and numerical simulations, we define the optimal fringe-sensor concepts and compute the expected performance of the four-telescope one with our dedicated end-to-end simulation tool sim2GFT. <BR /> Results: We first show that measuring the phase and the group delay by obtaining the data in several steps (i.e. by temporally modulating the optical path difference) is extremely sensitive to atmospheric turbulence and therefore conclude that it is better to obtain the fringe position with a set of data obtained simultaneously. Subsequently, we show that among all co-axial pairwise schemes, moderately redundant concepts increase the sensitivity as well as the robustness in various atmospheric or observing conditions. Merging all these results, end-to-end simulations show that our four-telescope fringe sensor concept is able to track fringes at least 90% of the time up to limiting magnitudes of 7.5 and 9.5 for the 1.8- and 8.2-meter VLTI telescopes respectively. [less ▲]

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See detailSpin-orbit alignment in planetary systems: what can we learn from resolved debris disks?
Absil, Olivier ULg

Scientific conference (2011, May 17)

Since the first detection of the spectroscopic transit of a hot Jupiter by Queloz et al. (2000), the Rossiter-McLaughlin effect, which allows the measurement of the sky-projected angle between the stellar ... [more ▼]

Since the first detection of the spectroscopic transit of a hot Jupiter by Queloz et al. (2000), the Rossiter-McLaughlin effect, which allows the measurement of the sky-projected angle between the stellar rotation axis and a planet's orbit axis, has been investigated for a large number of planetary systems. These observations have lead to the detection of spin-orbit misalignments for many hot Jupiters, and even of retrograde orbits in some cases (e.g., Triaud et al. 2010). Such misalignments are generally interpreted as the signature of either Kozai migration, or of planet-planet scattering followed by inward migration of the planet (e.g., Morton & Johnson 2011). However, it has recently been proposed that circumstellar disks themselves might not be aligned with the stellar spin axis due to either to early stellar encounters (Bate et al. 2010) or to magnetosphere-disk interactions (Lai et al. 2011). In this talk, I discuss how resolved debris disks may be used to settle this question, in particular by measuring the position angle of oblate stellar photospheres deformed by rapid rotation using spectro-interferometric measurements within the Brackett-gamma line. The method is illustrated by our recent study of Fomalhaut with VLTI/AMBER (Le Bouquin et al. 2009), which confirms the spin-orbit alignment with a high accuracy for the first time in a debris disk system. Possible implications on the nature of the dust grains composing the Fomalhaut debris disk will also be discussed. [less ▲]

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See detailA Herschel resolved far-infrared dust ring around HD 207129
Marshall, J. P.; Löhne, T.; Montesinos, B. et al

in Astronomy and Astrophysics (2011), 529

Context. Dusty debris discs around main sequence stars are thought to be the result of continuous collisional grinding of planetesimals in the system. The majority of these systems are unresolved and ... [more ▼]

Context. Dusty debris discs around main sequence stars are thought to be the result of continuous collisional grinding of planetesimals in the system. The majority of these systems are unresolved and analysis of the dust properties is limited by the lack of information regarding the dust location. <BR /> Aims: The Herschel DUNES key program is observing 133 nearby, Sun-like stars (<20 pc, FGK spectral type) in a volume limited survey to constrain the absolute incidence of cold dust around these stars by detection of far infrared excess emission at flux levels comparable to the Edgeworth-Kuiper belt (EKB). <BR /> Methods: We have observed the Sun-like star HD 207129 with Herschel PACS and SPIRE. In all three PACS bands we resolve a ring-like structure consistent with scattered light observations. Using α Boötis as a reference point spread function (PSF), we deconvolved the images, clearly resolving the inner gap in the disc at both 70 and 100 μm. <BR /> Results: We have resolved the dust-producing planetesimal belt of a debris disc at 100 μm for the first time. We measure the radial profile and fractional luminosity of the disc, and compare the values to those of discs around stars of similar age and/or spectral type, placing this disc in context of other resolved discs observed by Herschel/DUNES. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. [less ▲]

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See detailStudying debris disks with near‐infrared interferometry
Absil, Olivier ULg; Augereau, J.-C.; Le Bouquin, J.-B. et al

Conference (2011, April 13)

In this talk, I will describe and illustrate two different ways in which near-infrared stellar interferometry can be used to constrain the nature and physics of debris disks, and help understand the ... [more ▼]

In this talk, I will describe and illustrate two different ways in which near-infrared stellar interferometry can be used to constrain the nature and physics of debris disks, and help understand the global architecture of planetary systems in general. In the first part of the talk, I will review the on-going efforts to detect bright exozodiacal disks with precision near-infrared interferometry. I will describe the results of the exozodi survey that we are currently carrying out at the CHARA array, and briefly discuss our first results and perspectives with the new PIONIER instrument at the VLTI (including the identification of previously unknown low-mass companions). Preliminary statistical trends on the occurrence of bright exozodi around nearby main sequence stars will be presented, and I will discuss how this information could be used to constrain the global architecture and evolution of debris disks. In the second part of the talk, I will focus on our on-going project to characterize the “spin-orbit” alignment of resolved debris disks with the rotation axis of their (rapidly rotating) host star. Our first result obtained with the VLTI/AMBER spectro-interferometer on Fomalhaut will be presented, as well as its possible consequences on the dynamics of the planetary system and on the physics of the grains composing the Fomalhaut dust ring. I will then briefly describe the status and perspectives of this project. [less ▲]

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See detailImproving Interferometric null depth measurements using statistical distributions: theory and first results with the Palomar Fiber Nuller
Hanot, Charles ULg; Mennesson, Bertrand; Martin, Stefan et al

in Astrophysical Journal (2011), 729(2), 110

A new "self-calibrated" statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and ... [more ▼]

A new "self-calibrated" statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast atmospheric fluctuations. The approach yields an accuracy much better (about an order of magnitude) than is presently possible with standard data reduction methods, because the astrophysical null depth accuracy is no longer limited by the magnitude of the instrumental phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone—and no observations of calibrators—we find that error bars on the astrophysical null depth as low as a few 10–4 can be obtained in the near-infrared, which means that null depths lower than 10–3 can be reliably measured. This statistical analysis is not specific to our instrument and may be applicable to other interferometers. [less ▲]

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See detailExtra-solar planet imaging: ground vs space based coronagraphs
Hanot, Charles ULg; Absil, Olivier ULg; Boccaletti, A. et al

Conference (2010, October 28)

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast and angular resolution imaging has ... [more ▼]

In the context of exoplanet detection, a large majority of the 400 detected exoplanets have been found by indirect methods. Today, progress in the field of high contrast and angular resolution imaging has allowed direct images of several exoplanetary systems to be taken (cf. HR 8799, Fomalhaut and β Pic). In the near future, several new instruments are going to dramatically improve our sensitivity to exoplanet detection. Among these, SPHERE (Spectro Polarimetric High contrast Exoplanet REsearch) at the VLT, MIRI (Mid Infra-Red Instrument) onboard JWST and EPICS at the ELT will be equipped with coronagraphs to reveal faint objects in the vicinity of nearby stars. We made use of the Lyon group (COND) evolutionary models of young (sub-)stellar objects and exoplanets to compare the sensitivities of these different instruments using their estimated coronagraphic profiles. From this comparison, we present a catalogue of targets which are particularly well suited for the different instruments. [less ▲]

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See detailFirst manufactured diamond AGPM vector vortex for the L- and N-bands: metrology and expected performances
Delacroix, Christian ULg; Forsberg, Pontus; Karlsson, Mikael et al

Conference (2010, October 28)

The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period ... [more ▼]

The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) is an optical vectorial vortex coronagraph (or vector vortex) synthesized by a circular subwavelength grating, that is a grating with a period smaller than λ/n (λ being the observed wavelength and n the refractive index of the grating substrate). Since it is a phase mask, it allows to reach a high contrast with a small working angle. Moreover, its subwavelength structure provides a good achromatization over wide spectral bands. Recently, we have manufactured and measured our first N-band prototypes that allowed us to validate the reproducibility of the microfabrication process. Here, we present newly produced mid-IR diamond AGPMs in the N-band (~10 µm), and in the most wanted L-band (~3.5 µm). We first give an extrapolation of the expected coronagraph performances. We then present the manufacturing and measurement results, using diamond-optimized microfabrication techniques such as nano-imprint lithography (NIL) and reactive ion etching (RIE). Finally, the subwavelength grating profile metrology combines surface metrology (scanning electron microscopy, atomic force microscopy, white light interferometry) with diffractometry on an optical polarimetric bench and cross correlation with theoretical simulations using rigorous coupled wave analysis (RCWA). [less ▲]

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See detailA VLTI/AMBER closure-phase search for low-mass companions around nearby young stars: first results on beta Pictoris
Absil, Olivier ULg; Le Bouquin, J.-B.; Chauvin, G. et al

Conference (2010, October 25)

Young stars in nearby moving groups and associations are well suited to search for low-mass companions. In addition to their brightness, their proximity gives access to small linear separations and their ... [more ▼]

Young stars in nearby moving groups and associations are well suited to search for low-mass companions. In addition to their brightness, their proximity gives access to small linear separations and their youth makes potential low-mass companion brighter than around older main sequence stars. We have recently started a survey of such young nearby stars with the AMBER near-infrared interferometer at the VLTI. The closure phase measurements provided by AMBER on a triplet of baselines are particularly sensitive to nearby off-axis point-like sources. In this talk, we describe the first results of this survey obtained on beta Pictoris. Thanks to a closure phase accuracy of a few 0.1 degree, we show that a 3-sigma sensitivity of about 4e-3 can be reached on the contrast of potential companions for angular separations between 0.01 and 0.2 arcsec. This translates into a companion mass of about 35 Mjup from 0.2 to 4 AU in the case of beta Pictoris. We extrapolate this result on other stars of our survey and discuss the discovery space of AMBER. [less ▲]

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See detailInfluence of Exozodiacal Dust Clouds on Mid-IR Earth-like Planet Detection
Defrère, D.; Absil, Olivier ULg; den Hartog, R. et al

in Coudé du Foresto, Vincent; Gelino, Dawn; Ribas, Ignasi (Eds.) Pathways Towards Habitable Planets (2010, October 01)

The characterization of Earth-like extrasolar planets in the mid-infrared is a significant observational challenge that could be tackled by future space-based interferometers. A large effort has been ... [more ▼]

The characterization of Earth-like extrasolar planets in the mid-infrared is a significant observational challenge that could be tackled by future space-based interferometers. A large effort has been carried out the past two decades to define a design that provides the necessary scientific performance while minimizing cost and technical risks. These efforts have resulted in a consensus on a single mission architecture consisting of a non-coplanar X-array (the so-called Emma configuration), using four collector spacecraft and a single beam combiner spacecraft. The ability to study distant planets with an X-array interferometer will however depend on exozodiacal dust clouds, the counterparts of the solar zodiacal disk. In this paper, we briefly discuss the impact of exozodiacal clouds on the performance of an Emma X-array interferometer dedicated to Earth-like planet characterization. [less ▲]

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See detailThe Fourier-Kelvin Stellar Interferometer: Exploring Exoplanetary Systems with an Infrared Probe-class Mission
Barry, R. K.; Danchi, W. C.; Lopez, B. et al

in Coudé du Foresto, Vincent; Gelino, Dawn; Ribas, Ignasi (Eds.) Pathways Towards Habitable Planets (2010, October 01)

We report results of a recent engineering study of an enhanced version of the Fourier-Kelvin Stellar Interferometer (FKSI) that includes 1-m diameter primary mirrors, a 20-m baseline, a sun shield with a ... [more ▼]

We report results of a recent engineering study of an enhanced version of the Fourier-Kelvin Stellar Interferometer (FKSI) that includes 1-m diameter primary mirrors, a 20-m baseline, a sun shield with a ±45° Field-of-Regard (FoR), and 40K operating temperature. The enhanced FKSI is a two-element nulling interferometer operating in the mid-infrared (e.g. ˜ 5-15 μm) designed to measure exozodiacal debris disks around nearby stars with a sensitivity better than one solar system zodi (SSZ) and to characterize the atmospheres of a large sample of known exoplanets. The modifications to the original FKSI design also allows observations of the atmospheres of many super-Earths and a few Earth twins using a combination of spatial modulation and spectral analysis. [less ▲]

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See detailDo we Need to Solve the Exozodi Question? If Yes, How to Best Solve It?
Absil, Olivier ULg; Eiroa, C.; Augereau, J. et al

in Coudé du Foresto, Vincent; Gelino, Dawn; Ribas, Ignasi (Eds.) Pathways Towards Habitable Planets (2010, October 01)

When observing an extrasolar planetary system, the most luminous component after the star itself is generally the light scattered and/or thermally emitted by a population of micron-sized dust grains ... [more ▼]

When observing an extrasolar planetary system, the most luminous component after the star itself is generally the light scattered and/or thermally emitted by a population of micron-sized dust grains. These grains are expected to be continuously replenished by the collisions and evaporation of larger bodies just as in our solar zodiacal cloud. Exozodiacal clouds (“exozodis”) must therefore be seriously taken into account when attempting to directly image faint Earth-like planets (exoEarths, for short). This paper summarizes the oral contributions and discussions that took place during the Satellite Meeting on exozodiacal dust disks, in an attempt to address the following two questions: Do we need to solve the exozodi question? If yes, how to best solve it? [less ▲]

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See detailInfrared Detection and Characterization of Debris Disks, Exozodiacal Dust, and Exoplanets: The FKSI Mission Concept
Danchi, W. C.; Barry, R. K.; Lopez, B. et al

in Coudé du Foresto, Vincent; Gelino, Dawn; Ribas, Ignasi (Eds.) Pathways Towards Habitable Planets (2010, October 01)

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a nulling interferometer for the near-to-mid-infrared spectral region. FKSI is conceived as a mid-sized strategic or Probe class ... [more ▼]

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a nulling interferometer for the near-to-mid-infrared spectral region. FKSI is conceived as a mid-sized strategic or Probe class mission. FKSI has been endorsed by the Exoplanet Community Forum 2008 as such a mission and has been costed to be within the expected budget. The current design of FKSI is a two-element nulling interferometer. The two telescopes, separated by 12.5m, are precisely pointed (by small steering mirrors) on the target star. The two path lengths are accurately controlled to be the same to within a few nanometers. A phase shifter/beam combiner (Mach-Zehnder interferometer) produces an output beam consisting of the nulled sum of the target planet’s light and the host star’s light. When properly oriented, the starlight is nulled by a factor of 10[SUP]-4[/SUP], and the planet light is undiminished. Accurate modeling of the signal is used to subtract the residual starlight, permitting the detection of planets much fainter than the host star. The current version of FKSI with 0.5-m apertures and waveband 3-8 μm has the following main capabilities: (1) detect exozodiacal emission levels to that of our own solar system (Solar System Zodi) around nearby F, G, and K stars; (2) characterize spectroscopically the atmospheres of a large number of known non-transiting planets; (3) survey and characterize nearby stars for planets down to 2 R[SUB]earth[/SUB] from just inside the habitable zone and inward. An enhanced version of FKSI with 1-m apertures separated by 20 m and cooled to 40 K, with science waveband 5-15 μm, allows for the detection and characterization of 2 R[SUB]earth[/SUB] super-Earths and smaller planets in the habitable zone around stars within about 30 pc. [less ▲]

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See detailMulti-Aperture Imaging of Extrasolar Planetary Systems
Absil, Olivier ULg

in Coudé du Foresto, Vincent; Gelino, Dawn; Ribas, Ignasi (Eds.) Pathways Towards Habitable Planets (2010, October 01)

In this paper, we review the various ways in which an infrared stellar interferometer can be used to perform direct detection of extrasolar planetary systems. We first review the techniques based on ... [more ▼]

In this paper, we review the various ways in which an infrared stellar interferometer can be used to perform direct detection of extrasolar planetary systems. We first review the techniques based on classical stellar interferometry, where (complex) visibilities are measured, and then describe how higher dynamic ranges can be achieved with nulling interferometry. The application of nulling interferometry to the study of exozodiacal discs and extrasolar planets is then discussed and illustrated with a few examples. [less ▲]

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See detailDeep near-infrared interferometric search for low-mass companions around β Pictoris
Absil, Olivier ULg; Le Bouquin, Jean-Baptiste; Lebreton, Jérémy et al

in Astronomy and Astrophysics (2010), 520

Aims. We search for low-mass companions in the innermost region (<300 mas, i.e., 6 AU) of the β Pic planetary system. Methods. We obtained interferometric closure phase measurements in the K-band with the ... [more ▼]

Aims. We search for low-mass companions in the innermost region (<300 mas, i.e., 6 AU) of the β Pic planetary system. Methods. We obtained interferometric closure phase measurements in the K-band with the VLTI/AMBER instrument used in its medium spectral resolution mode. Fringe stabilization was provided by the FINITO fringe tracker. Results. In a search region of between 2 and 60 mas in radius, our observations exclude at 3σ significance the presence of companions with K-band contrasts greater than 5×10^-3 for 90% of the possible positions in the search zone (i.e., 90% completeness). The median 1σ error bar in the contrast of potential companions within our search region is 1.2×10^-3. The best fit to our data set using a binary model is found for a faint companion located at about 14.4 mas from β Pic, which has a contrast of 1.8×10^-3 ± 1.1×10^-3 (a result consistent with the absence of companions). For angular separations larger than 60 mas, both time smearing and field-of-view limitations reduce the sensitivity. Conclusions. We can exclude the presence of brown dwarfs with masses higher than 29 MJup (resp. 47 MJup) at a 50% (resp. 90%) completeness level within the first few AUs around β Pic. Interferometric closure phases offer a promising way to directly image low-mass companions in the close environment of nearby young stars. [less ▲]

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