arXiv subjects

Lucas Labadie

Publications and source records attributed to Lucas Labadie.

At least 55 records · Page 3Linked to original sources

arXiv2017

Completing the puzzle: AOLI full-commissioning fresh results and AIV innovations

The Adaptive Optics Lucky Imager (AOLI) is a new instrument designed to combine adaptive optics (AO) and lucky imaging (LI) techniques to deliver high spatial resolution in the visible, 20 mas, from ground-based telescopes. Here we present details of the integration and verification phases explaining the defiance that we have faced and the innovative and versatile solution of modular integration for each of its subsystems that we have developed. Modularity seems a clue key for opto-mechanical integration success in the extremely-big telescopes era. We present here the very fresh preliminary results after its first fully-working observing run on the WHT.

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arXiv2016

Beam combination schemes and technologies for the Planet Formation Imager (PFI)

The Planet Formation Imager (PFI) initiative aims at developing the next generation large scale facility for imaging astronomical optical interferometry operating in the mid-infrared. Here we report on the progress of the Planet Formation Imager Technical Working Group on the beam-combination instruments. We will discuss various available options for the science and fringe-tracker beam combination instruments, ranging from direct imaging, to non-redundant fiber arrays, to integrated optics solutions. Besides considering basic characteristics of the schemes, we will investigate the maturity of the available technological platforms at near- and mid-infrared wavelengths.

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arXiv2016

Planet Formation Imager (PFI): science vision and key requirements

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to about 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs.

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arXiv2016

An instrumental puzzle: the modular integration of AOLI

The Adaptive Optics Lucky Imager, AOLI, is an instrument developed to deliver the highest spatial resolution ever obtained in the visible, 20 mas, from ground-based telescopes. In AOLI a new philosophy of instrumental prototyping has been applied, based on the modularization of the subsystems. This modular concept offers maximum flexibility regarding the instrument, telescope or the addition of future developments.

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arXiv2016

AOLI: Near-diffraction limited imaging in the visible on large ground-based telescopes

The combination of Lucky Imaging with a low order adaptive optics system was demonstrated very successfully on the Palomar 5m telescope nearly 10 years ago. It is still the only system to give such high-resolution images in the visible or near infrared on ground-based telescope of faint astronomical targets. The development of AOLI for deployment initially on the WHT 4.2 m telescope in La Palma, Canary Islands, will be described in this paper. In particular, we will look at the design and status of our low order curvature wavefront sensor which has been somewhat simplified to make it more efficient, ensuring coverage over much of the sky with natural guide stars as reference object. AOLI uses optically butted electron multiplying CCDs to give an imaging array of 2000 x 2000 pixels.

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arXiv2016

Astronomical photonics in the context of infrared interferometry and high-resolution spectroscopy

We review the potential of Astrophotonics, a relatively young field at the interface between photonics and astronomical instrumentation, for spectro-interferometry. We review some fundamental aspects of photonic science that drove the emer- gence of astrophotonics, and highlight the achievements in observational astrophysics. We analyze the prospects for further technological development also considering the potential synergies with other fields of physics (e.g. non-linear optics in condensed matter physics). We also stress the central role of fiber optics in routing and transporting light, delivering complex filters, or interfacing instruments and telescopes, more specifically in the context of a growing usage of adaptive optics.

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arXiv2016

Performance estimates for spectrographs using photonic reformatters

Using a photonic reformatter to eliminate the effects of conventional modal noise could greatly improve the stability of a high resolution spectrograph. However the regimes where this advantage becomes clear are not yet defined. Here we will look at where modal noise becomes a problem in conventional high resolution spectroscopy and what impact photonic spectrographs could have. We will theoretically derive achievable radial velocity measurements to compare photonic instruments and conventional ones. We will discuss the theoretical and experimental investigations that will need to be undertaken to optimize and prove the photonic reformatting concept.

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arXiv2016

A novel high-contrast imaging technique based on optical tunneling to search for faint companions around bright stars at the limit of diffraction

We present a novel application of optical tunneling in the context of high-angular resolution, high-contrast techniques with the aim of improving direct imaging capabilities of faint companions in the vicinity of bright stars. In contrast to existing techniques like coronagraphy, we apply well-established techniques from integrated optics to exclusively extinct a very narrow angular direction coming from the sky. This extinction is achieved in the pupil plane and does not suffer from diffraction pattern residuals. We give a comprehensive presentation of the underlying theory as well as first laboratory results.

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arXiv2015

Impact of ηearth on the capabilities of affordable space missions to detect biosignatures on extrasolar planets

We present an analytic model to estimate the capabilities of space missions dedicated to the search for biosignatures in the atmosphere of rocky planets located in the habitable zone of nearby stars. Relations between performance and mission parameters such as mirror diameter, distance to targets, and radius of planets, are obtained. Two types of instruments are considered: coronagraphs observing in the visible, and nulling interferometers in the thermal infrared. Missions considered are: single-pupil coronagraphs with a 2.4 m primary mirror, and formation flying interferometers with 4 x 0.75 m collecting mirrors. The numbers of accessible planets are calculated as a function of ηearth. When Kepler gives its final estimation for ηearth, the model will permit a precise assessment of the potential of each instrument. Based on current estimations, ηearth = 10% around FGK stars and 50% around M stars, the coronagraph could study in spectroscopy only ~1.5 relevant planets, and the interferometer ~14.0. These numbers are obtained under the major hypothesis that the exozodiacal light around the target stars is low enough for each instrument. In both cases, a prior detection of planets is assumed and a target list established. For the long-term future, building both types of spectroscopic instruments, and using them on the same targets, will be the optimal solution because they provide complementary information. But as a first affordable space mission, the interferometer looks the more promising in term of biosignature harvest.

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arXiv2014

Ultrafast laser inscription of mid-IR directional couplers for stellar interferometry

We report the ultrafast laser fabrication and mid-IR characterization (3.39 microns) of four-port evanescent field directional couplers. The couplers were fabricated in a commercial gallium lanthanum sulphide glass substrate using sub-picosecond laser pulses of 1030 nm light. Straight waveguides inscribed using optimal fabrication parameters were found to exhibit propagation losses of 0.8 dB/cm. A series of couplers were inscribed with different interaction lengths, and we demonstrate power splitting ratios of between 8% and 99% for mid-IR light with a wavelength of 3.39 microns. These results clearly demonstrate that ultrafast laser inscription can be used to fabricate high quality evanescent field couplers for future applications in astronomical interferometry.

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arXiv2014

HD139614: the interferometric case for a group-Ib pre-transitional young disk

The Herbig Ae star HD 139614 is a group-Ib object, which featureless SED indicates disk flaring and a possible pre-transitional evolutionary stage. We present mid- and near-IR interferometric results collected with MIDI, AMBER and PIONIER with the aim of constraining the spatial structure of the 0.1-10 AU disk region and assess its possible multi-component structure. A two-component disk model composed of an optically thin 2-AU wide inner disk and an outer temperature-gradient disk starting at 5.6 AU reproduces well the observations. This is an additional argument to the idea that group-I HAeBe inner disks could be already in the disk-clearing transient stage. HD 139614 will become a prime target for mid-IR interferometric imaging with the second-generation instrument MATISSE of the VLTI.

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arXiv2014

High-Resolution Imaging in the Visible on Large Ground-Based Telescopes

Lucky Imaging combined with a low order adaptive optics system has given the highest resolution images ever taken in the visible or near infrared of faint astronomical objects. This paper describes a new instrument that has already been deployed on the WHT 4.2m telescope on La Palma, with particular emphasis on the optical design and the predicted system performance. A new design of low order wavefront sensor using photon counting CCD detectors and multi-plane curvature wavefront sensor will allow virtually full sky coverage with faint natural guide stars. With a 2 x 2 array of 1024 x 1024 photon counting EMCCDs, AOLI is the first of the new class of high sensitivity, near diffraction limited imaging systems giving higher resolution in the visible from the ground than hitherto been possible from space.

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arXiv2014

The Science Case for the Planet Formation Imager (PFI)

Among the most fascinating and hotly-debated areas in contemporary astrophysics are the means by which planetary systems are assembled from the large rotating disks of gas and dust which attend a stellar birth. Although important work has already been, and is still being done both in theory and observation, a full understanding of the physics of planet formation can only be achieved by opening observational windows able to directly witness the process in action. The key requirement is then to probe planet-forming systems at the natural spatial scales over which material is being assembled. By definition, this is the so-called Hill Sphere which delineates the region of influence of a gravitating body within its surrounding environment. The Planet Formation Imager project (PFI) has crystallized around this challenging goal: to deliver resolved images of Hill-Sphere-sized structures within candidate planet-hosting disks in the nearest star-forming regions. In this contribution we outline the primary science case of PFI. For this purpose, we briefly review our knowledge about the planet-formation process and discuss recent observational results that have been obtained on the class of transition disks. Spectro-photometric and multi-wavelength interferometric studies of these systems revealed the presence of extended gaps and complex density inhomogeneities that might be triggered by orbiting planets. We present detailed 3-D radiation-hydrodynamic simulations of disks with single and multiple embedded planets, from which we compute synthetic images at near-infrared, mid-infrared, far-infrared, and sub-millimeter wavelengths, enabling a direct comparison of the signatures that are detectable with PFI and complementary facilities such as ALMA. From these simulations, we derive some preliminary specifications that will guide the array design and technology roadmap of the facility.

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arXiv2014

Planet Formation Imager (PFI): Introduction and Technical Considerations

Complex non-linear and dynamic processes lie at the heart of the planet formation process. Through numerical simulation and basic observational constraints, the basics of planet formation are now coming into focus. High resolution imaging at a range of wavelengths will give us a glimpse into the past of our own solar system and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions. Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals and from here we launch our planning efforts. The aim of the "Planet Formation Imager" (PFI) project is to develop the roadmap for the construction of a new near-/mid-infrared interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. PFI will be able to detect the emission of the cooling, newly-formed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Here we introduce the Planet Formation Imager (PFI) Project (www.planetformationimager.org) and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements.

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arXiv2014

Integrated optics interferometric four telescopes nuller

Nulling interferometry has been identified as a competitive technique for the detection of extrasolar planets. The technique consists in combining out-of-phase pairs of telescopes to null effectively the light of a bright star an reveal the dim glow of the companion. We have manufactured and tested with monochromatic light an integrated optics component which combines a linear array of 4 telescopes in the nulling mode envisaged by Angel & Wolf (1997). Our testbench simulates the motion of a star in the sky. The tests have demonstrated a nulling scaling as the fourth power of the baseline delay.

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arXiv2014

Perspective for optical high-angular resolution follow-up studies of X-raying AGNs

We explore the scientific potential of next-generation high-angular resolution optical imager to study the AGN/Host connection. The availability of a significant number of X-raying AGN with natural guide stars, allowing for adaptive optics at optical wavelengths, offers an interesting perspective to complement high-resolution work currently done in the near-infrared.

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arXiv2013

Evidence of a discontinuous disk structure around the Herbig Ae star HD 139 614

A new class of pre-main sequence objects has been recently identified as pre-transitional disks. They present near-infrared excess coupled to a flux deficit at about 10 microns and a rising mid-infrared and far-infrared spectrum. These features suggest a disk structure with inner and outer dust components, separated by a dust-depleted region (or gap). We here report on the first interferometric observations of the disk around the Herbig Ae star HD 139614. Its infrared spectrum suggests a flared disk, and presents pre-transitional features,namely a substantial near-infrared excess accompanied by a dip around 6 microns and a rising mid-infrared part. In this framework, we performed a study of the spectral energy distribution (SED) and the mid-infrared VLTI/MIDI interferometric data to constrain thespatial structure of the inner dust disk region and assess its possibly multi-component structure. We based our work on a temperature-gradient disk model that includes dust opacity. While we could not reproduce the SED and interferometric visibilities with a one-component disk, a better agreement was obtained with a two-component disk model composed of an optically thin inner disk extending from 0.22 to 2.3 au, a gap, and an outer temperature-gradient disk starting at 5.6 au. Therefore, our modeling favors an extended and optically thin inner dust component and in principle rules out the possibility that the near-infrared excess originates only from a spatially confined region. Moreover, the outer disk is characterized by a very steep temperature profile and a temperature higher than 300 K at its inner edge. This suggests the existence of a warm component corresponding to a scenario where the inner edge of the outer disk is directly illuminated by the central star. This is an expected consequence of the presence of a gap, thus indicative of a pre-transitional structure.

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arXiv2012

AOLI-- Adaptive Optics Lucky Imager: Diffraction Limited Imaging in the Visible on Large Ground-Based Telescopes

The highest resolution images ever taken in the visible were obtained by combining Lucky Imaging and low order adaptive optics. This paper describes a new instrument to be deployed on the WHT 4.2m and GTC 10.4 m telescopes on La Palma, with particular emphasis on the optical design and the expected system performance. A new design of low order wavefront sensor using photon counting CCD detectors and multi-plane curvature wavefront sensor will allow dramatically fainter reference stars to be used, allowing virtually full sky coverage with a natural guide star. This paper also describes a significant improvements in the efficiency of Lucky Imaging, important advances in wavefront reconstruction with curvature sensors and the results of simulations and sensitivity limits. With a 2 x 2 array of 1024 x 1024 photon counting EMCCDs, AOLI is likely to be the first of the new class of high sensitivity, near diffraction limited imaging systems giving higher resolution in the visible from the ground than hitherto been possible from space.

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