References of "Le Bouquin, J.-B"
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See detailUnraveling the Mystery of Exozodiacal Dust
Ertel, S.; Augereau, J.-C.; Thébault, P. et al

in Booth, Mark; Matthews, Brenda; Graham, James (Eds.) Exploring the Formation and Evolution of Planetary Systems (2014, January 01)

Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary ... [more ▼]

Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the Habitable Zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemispheres. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. We focus here on presenting the observational work carried out by our team. [less ▲]

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See detailThree-dimensional orbits of the triple-O stellar system HD 150136
Sana, H.; Le Bouquin, J.-B.; Mahy, Laurent et al

in Astronomy and Astrophysics (2013), 553

Context. HD 150136 is a triple hierarchical system and a non-thermal radio emitter. It is formed by an O3-3.5 V + O5.5-6 V close binary and a more distant O6.5-7 V tertiary. So far, only the inner orbital ... [more ▼]

Context. HD 150136 is a triple hierarchical system and a non-thermal radio emitter. It is formed by an O3-3.5 V + O5.5-6 V close binary and a more distant O6.5-7 V tertiary. So far, only the inner orbital properties have been reliably constrained. Aims. To quantitatively understand the non-thermal emission process, accurate knowledge of the physical and orbital properties of the object is crucial. Here, we aim to investigate the orbital properties of the wide system and to constrain the inclinations of the inner and outer binaries, and with these the absolute masses of the system components. Methods. We used the PIONIER combiner at the Very Large Telescope Interferometer to obtain the very first interferometric measurements of HD 150136. We combined the interferometric observations with new and existing high resolution spectroscopic data to derive the orbital solution of the outer companion in the three-dimensional space. Results. The wide system is clearly resolved by PIONIER, with a projected separation on the plane of the sky of about 9 milli-arcsec. The best-fit orbital period, eccentricity, and inclination are 8.2 yr, 0.73 and 108 degr. We constrain the masses of the three stars of the system to 63 +/- 10, 40 +/- 6, and 33 +/- 12 Msun for the O3-3.5 V, O5.5-6 V and O6.5-7 V components. Conclusions. The dynamical masses agree within errors with the evolutionary masses of the components. Future interferometric and spectroscopic monitoring of HD 150136 should allow one to reduce the uncertainties to a few per cent only and to accurately constrain the distance to the system. This makes HD 150136 an ideal system to quantitatively test evolutionary models of high-mass stars as well as the physics of non-thermal processes occurring in O-type systems. [less ▲]

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See detailHot circumstellar material resolved around β Pic with VLTI/PIONIER
Defrère, D.; Lebreton, J.; Le Bouquin, J.-B. et al

in Astronomy and Astrophysics (2012), 546

Aims: We aim at resolving the circumstellar environment around β Pic in the near-infrared in order to study the inner planetary system (<200 mas, i.e., ~4 AU). Methods: Precise interferometric fringe ... [more ▼]

Aims: We aim at resolving the circumstellar environment around β Pic in the near-infrared in order to study the inner planetary system (<200 mas, i.e., ~4 AU). Methods: Precise interferometric fringe visibility measurements were obtained over seven spectral channels dispersed across the H band with the four-telescope VLTI/PIONIER interferometer. Thorough analysis of interferometric data was performed to measure the stellar angular diameter and to search for circumstellar material. Results: We detected near-infrared circumstellar emission around β Pic that accounts for 1.37% ± 0.16% of the near-infrared stellar flux and that is located within the field-of-view of PIONIER (i.e., ~200 mas in radius). The flux ratio between this excess and the photosphere emission is shown to be stable over a period of 1 year and to vary only weakly across the H band, suggesting that the source is either very hot (≳1500 K) or dominated by the scattering of the stellar flux. In addition, we derive the limb-darkened angular diameter of β Pic with an unprecedented accuracy (θLD= 0.736 ± 0.019 mas). Conclusions: The presence of a small H-band excess originating in the vicinity of β Pic is revealed for the first time thanks to the high-precision visibilities enabled by VLTI/PIONIER. This excess emission is likely due to the scattering of stellar light by circumstellar dust and/or the thermal emission from a yet unknown population of hot dust, although hot gas emitting in the continuum cannot be firmly excluded. [less ▲]

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See detailBinary Interaction Dominates the Evolution of Massive Stars
Sana, H.; de Mink, S. E.; de Koter, A. et al

in Science (2012), 337(6093), 444-446

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on ... [more ▼]

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae. [less ▲]

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See detailThe long period eccentric orbit of the particle accelerator HD 167971 revealed by long baseline interferometry
De Becker, Michaël ULg; Sana, H; Absil, Olivier ULg et al

in Monthly Notices of the Royal Astronomical Society (2012), 423

Using optical long baseline interferometry, we resolved for the first time the two wide components of HD167971, a candidate hierarchical triple system known to efficiently accelerate particles. Our multi ... [more ▼]

Using optical long baseline interferometry, we resolved for the first time the two wide components of HD167971, a candidate hierarchical triple system known to efficiently accelerate particles. Our multi-epoch VLTI observations provide direct evidence for a gravitational link between the O8 supergiant and the close eclipsing O + O binary. The separation varies from 8 to 15 mas over the three-year baseline of our observations, suggesting that the components evolve on a wide and very eccentric orbit (most probably e>0.5). These results provide evidence that the wide orbit revealed by our study is not coplanar with the orbit of the inner eclipsing binary. From our measurements of the near-infrared luminosity ratio, we constrain the spectral classification of the components in the close binary to be O6-O7, and confirm that these stars are likely main-sequence objects. Our results are discussed in the context of the bright non-thermal radio emission already reported for this system, and we provide arguments in favour of a maximum radio emission coincident with periastron passage. HD167971 turns out to be an efficient O-type particle accelerator that constitutes a valuable target for future high angular resolution radio imaging using VLBI facilities. [less ▲]

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See detailPIONIER: a 4-telescope visitor instrument at VLTI
Le Bouquin, J.-B.; Berger, J.-P.; Lazareff, B. et al

in Astronomy and Astrophysics (2011), 535

Context. PIONIER stands for Precision Integrated-Optics Near-infrared Imaging ExpeRiment. It combines four 1.8m Auxilliary Telescopes or four 8m Unit Telescopes of the Very Large Telescope Interferometer ... [more ▼]

Context. PIONIER stands for Precision Integrated-Optics Near-infrared Imaging ExpeRiment. It combines four 1.8m Auxilliary Telescopes or four 8m Unit Telescopes of the Very Large Telescope Interferometer (ESO, Chile) using an integrated optics combiner. The instrument was integrated at IPAG in December 2009 and commissioned at the Paranal Observatory in October 2010. It has provided scientific observations since November 2010. <BR /> Aims: In this paper, we explain the instrumental concept and describe the standard operational modes and the data reduction strategy. We present the typical performance and discuss how to improve them. <BR /> Methods: This paper is based on laboratory data obtained during the integrations at IPAG, as well as on-sky data gathered during the commissioning at VLTI. We illustrate the imaging capability of PIONIER on the binaries δ Sco and HIP11231. <BR /> Results: PIONIER provides six visibilities and three independent closure phases in the H band, either in a broadband mode or with a low spectral dispersion (R = 40), using natural light (i.e. unpolarized). The limiting magnitude is Hmag = 7 in dispersed mode under median atmospheric conditions (seeing < 1, τ[SUB]0[/SUB] > 3ms) with the 1.8m Auxiliary Telescopes. We demonstrate a precision of 0.5deg on the closure phases. The precision on the calibrated visibilities ranges from 3% to 15% depending on the atmospheric conditions. <BR /> Conclusions: PIONIER was installed and successfully tested as a visitor instrument for the VLTI. It permits high angular resolution imaging studies at an unprecedented level of sensitivity. The successful combination of the four 8m Unit Telescopes in March 2011 demonstrates that VLTI is ready for four-telescope operation. Based on observations collected at the European Southern Observatory, Paranal, Chile (commissioning data and 087.C-0709). [less ▲]

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See detailSearching for faint companions with VLTI/PIONIER. I. Method and first results
Absil, Olivier ULg; Le Bouquin, J.-B.; Berger, J.-P. et al

in Astronomy and Astrophysics (2011), 535

Context. A new four-telescope interferometric instrument called PIONIER has recently been installed at VLTI. It provides improved imaging capabilities together with high precision. <BR /> Aims: We search ... [more ▼]

Context. A new four-telescope interferometric instrument called PIONIER has recently been installed at VLTI. It provides improved imaging capabilities together with high precision. <BR /> Aims: We search for low-mass companions around a few bright stars using different strategies, and determine the dynamic range currently reachable with PIONIER. <BR /> Methods: Our method is based on the closure phase, which is the most robust interferometric quantity when searching for faint companions. We computed the χ[SUP]2[/SUP] goodness of fit for a series of binary star models at different positions and with various flux ratios. The resulting χ[SUP]2[/SUP] cube was used to identify the best-fit binary model and evaluate its significance, or to determine upper limits on the companion flux in case of non-detections. <BR /> Results: No companion is found around <ASTROBJ>Fomalhaut</ASTROBJ>, <ASTROBJ>tau Cet</ASTROBJ> and <ASTROBJ>Regulus</ASTROBJ>. The median upper limits at 3σ on the companion flux ratio are respectively of 2.3 × 10[SUP]-3[/SUP] (in 4 h), 3.5 × 10[SUP]-3[/SUP] (in 3 h) and 5.4 × 10[SUP]-3[/SUP] (in 1.5 h) on the search region extending from 5 to 100 mas. Our observations confirm that the previously detected near-infrared excess emissions around Fomalhaut and tau Cet are not related to a low-mass companion, and instead come from an extended source such as an exozodiacal disk. In the case of <ASTROBJ>del Aqr</ASTROBJ>, in 30 min of observation, we obtain the first direct detection of a previously known companion, at an angular distance of about 40 mas and with a flux ratio of 2.05 × 10[SUP]-2[/SUP] ± 0.16 × 10[SUP]-2[/SUP]. Due to the limited u,v plane coverage, its position can, however, not be unambiguously determined. <BR /> Conclusions: After only a few months of operation, PIONIER has already achieved one of the best dynamic ranges world-wide for multi-aperture interferometers. A dynamic range up to about 1:500 is demonstrated on unresolved targets, but significant improvements are still required to reach the ultimate goal of directly detecting hot giant extrasolar planets. Based on observations obtained at the European Southern Observatory (ESO) Very Large Telescope Interferometer (VLTI), Paranal, Chile. [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 Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry
Sana, H.; Le Bouquin, J.-B.; De Becker, Michaël ULg et al

in Astrophysical Journal Letters (2011), 740

As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been ... [more ▼]

As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been invoked to explain its X-ray properties: wind-wind interaction and magnetic wind confinement. Yet, HD 93250 shows absolutely constant radial velocities over timescales of years suggesting either a single star, a binary system seen pole-on view or a very long period, and/or highly eccentric system. Using the ESO Very Large Telescope Interferometer, we resolved HD 93250 as a close pair with similar components. We measured a near-infrared flux ratio of 0.8 ± 0.1 and a separation of (1.5 ± 0.2) × 10-3 arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 AU. While a quantitative investigation would require a full characterization of the orbit, the binary nature of HD 93250 allows us to qualitatively explain both its X-ray flux and hardness and its non-thermal radio emission in the framework of a colliding wind scenario. We also discuss various observational biases. We show that, due to line blending of two similar spectral components, HD 93250 could have a period as short as 1 to several years despite the lack of measurable radial velocity variations. [less ▲]

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See detailThe size of AB Doradus A from VLTI/AMBER interferometry
Guirado, J. C.; Marcaide, J. M.; Martí-Vidal, I. et al

in Astronomy and Astrophysics (2011), 533

The pre-main sequence (PMS) star AB Dor A is the main component of the quadruple system AB Doradus. The precise determination of the mass and photometry of the close companion to AB Dor A, AB Dor C, has ... [more ▼]

The pre-main sequence (PMS) star AB Dor A is the main component of the quadruple system AB Doradus. The precise determination of the mass and photometry of the close companion to AB Dor A, AB Dor C, has provided an important benchmark for calibration of theoretical evolutionary models of low-mass stars. The limiting factor to the precision of this calibration is the age of the system, as both the mass and luminosity of AB Dor A and C are well monitored by other ongoing programs. In this paper we present VLTI/AMBER observations of AB Dor A which provide a direct measurement of the size of this star, 0.96 ± 0.06 R[SUB]&sun;[/SUB]. The latter estimate, combined with other fundamental parameters also measured for this star, allows a precise test of PMS evolutionary models using both H-R diagrams and mass-radius relationships. We have found that our radius measurement is larger than that predicted by the models, which we interpret as an evidence of the oversizing produced by the strong magnetic activity of AB Dor A. Considering, at least partially, this magnetic effect, theoretical isochrones have been used to derive constraints to the age of AB Dor A, favouring an age about 40-50 Myr for this system. Older ages are not completely excluded by our data. Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 384.C-1053. [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 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 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 detailPIONIER: a visitor instrument for VLTI
Berger, Jean-Philippe; Zins, G.; Lazareff, B. et al

in Danchi, W. C.; Delplancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used ... [more ▼]

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used in scanning mode. It provides low spectral resolution in H and K band. PIONIER is designed for imaging with a specific emphasis on fast fringe recording to allow closure-phases and visibilities to be precisely measured. In this work we provide the detailed description of the instrument and present its updated status. [less ▲]

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See detailThe Fomalhaut debris disk seen from every angle with interferometry
Absil, Olivier ULg; Mennesson, B.; Le Bouquin, J.-B. et al

in Danchi, W. C.; Delplancke, F.; Rajagopal, J. K. (Eds.) Optical and Infrared Interferometry II (2010, July)

In this paper, we present the results of three different studies of the Fomalhaut debris disk with infrared interferometry. First, VLTI/AMBER measurements are used to determine the position angle of the ... [more ▼]

In this paper, we present the results of three different studies of the Fomalhaut debris disk with infrared interferometry. First, VLTI/AMBER measurements are used to determine the position angle of the slightly oblate rapidly rotating photosphere by means of differential phase measurements across the Br-gamma photospheric line. This measurement allows us to confirm that the debris disk is located in the equatorial plane of its host star. Second, we use VLTI/VINCI to search for resolved near-infrared emission around the stellar photosphere, which would correspond to the presence of large amounts of hot dust grains located between the sublimation radius and the habitable zone. Our observations reveal a small excess of 0.88%+/-0.12% in K band relative to the photospheric flux. Finally, we use the Keck Interferometer Nuller in order to derive additional constraints on the nature of the resolved infrared emission. Our observations suggest a marginal detection of a circumstellar excess at 10 μm, which we use together with the VINCI detection to model the circumstellar emission. Preliminary results from this modeling effort are discussed. [less ▲]

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See detailThe spin-orbit alignment of the Fomalhaut planetary system probed by optical long baseline interferometry
Le Bouquin, J.-B.; Absil, Olivier ULg; Benisty, M. et al

in Astronomy and Astrophysics (2009), 498

Aims. We discuss the spin-orbit orientation of the Fomalhaut planetary system composed of a central A4V star, a debris disk, and a recently discovered planetary companion. Methods: We use spectrally ... [more ▼]

Aims. We discuss the spin-orbit orientation of the Fomalhaut planetary system composed of a central A4V star, a debris disk, and a recently discovered planetary companion. Methods: We use spectrally resolved, near-IR long baseline interferometry to obtain precise spectro-astrometric measurements across the Br-gamma absorption line. The achieved astrometric accuracy of ±3 muas and the spectral resolution R=1500 from the AMBER/VLTI instrument allow us to spatially and spectrally resolve the rotating photosphere. Results: We find a position angle PA(star)=65° ± 3° for the stellar rotation axis, perpendicular to the literature measurement for the disk position angle (PA(disk)=156.0 ° ± 0.3°). This is the first time such a test could be performed for a debris disk, and in a non-eclipsing system. Additionally, our measurements suggest unexpected backward-scattering properties for the circumstellar dust grains. Conclusions: Our observations validate the standard scenario for star and planet formation in which the angular momentum of the planetary systems are expected to be colinear with the stellar spins. Based on observations collected at the VLTI (ESO Paranal, Chile), with the 082.C-0376 program from the AMBER Guaranteed Time of the Osservatorio Astrofisico di Arcetri (INAF, Italy). [less ▲]

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See detailMilli-arcsecond Astrophysics with VSI, the VLTI Spectro-imager in the ELT Era
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Moorwood, Alan (Ed.) Science with the VLT in the ELT Era (2009)

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be ... [more ▼]

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be investigated at milli-arcsecond scales only with the VLT in its interferometric mode. We propose a spectro-imager, named VSI (VLTI spectro-imager), which is capable to probe these sources both over spatial and spectral scales in the near-infrared domain. This instrument will provide information complementary to what is obtained at the same time with ALMA at different wavelengths and the extreme large telescopes. [less ▲]

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See detailVSI: the VLTI spectro-imager
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at ... [more ▼]

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions down to 1.1 milliarcsecond and spectral resolutions up to R = 12000. Targets as faint as K = 13 will be imaged without requiring a brighter nearby reference object; fainter targets can be accessed if a suitable reference is available. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral resolution enables a scientific program which serves a broad user community and at the same time provides the opportunity for breakthroughs in many areas of astrophysics. The high level specifications of the instrument are derived from a detailed science case based on the capability to obtain, for the first time, milliarcsecond-resolution images of a wide range of targets including: probing the initial conditions for planet formation in the AU-scale environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities using technologies which have been extensively tested in the past and VSI requires little in terms of new infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize the scientific return. [less ▲]

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See detailSystem overview of the VLTI Spectro-Imager
Jocou, L.; Berger, J.-P.; Malbet, F. et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

The VLTI Spectro Imager project aims to perform imaging with a temporal resolution of 1 night and with a maximum angular resolution of 1 milliarcsecond, making best use of the Very Large Telescope ... [more ▼]

The VLTI Spectro Imager project aims to perform imaging with a temporal resolution of 1 night and with a maximum angular resolution of 1 milliarcsecond, making best use of the Very Large Telescope Interferometer capabilities. To fulfill the scientific goals (see Garcia et. al.), the system requirements are: a) combining 4 to 6 beams; b) working in spectral bands J, H and K; c) spectral resolution from R= 100 to 12000; and d) internal fringe tracking on-axis, or off-axis when associated to the PRIMA dual-beam facility. The concept of VSI consists on 6 sub-systems: a common path distributing the light between the fringe tracker and the scientific instrument, the fringe tracker ensuring the co-phasing of the array, the scientific instrument delivering the interferometric observables and a calibration tool providing sources for internal alignment and interferometric calibrations. The two remaining sub-systems are the control system and the observation support software dedicated to the reduction of the interferometric data. This paper presents the global concept of VSI science path including the common path, the scientific instrument and the calibration tool. The scientific combination using a set of integrated optics multi-way beam combiners to provide high-stability visibility and closure phase measurements are also described. Finally we will address the performance budget of the global VSI instrument. The fringe tracker and scientific spectrograph will be shortly described. [less ▲]

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