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See detailLIFE: Large Interferometer For Exoplanet
Defrere, Denis ULiege

Scientific conference (2019, February 04)

Overview of the LIFE project

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See detailDeep Exploration of ɛ Eridani with Keck Ms-band Vortex Coronagraphy and Radial Velocities: Mass and Orbital Parameters of the Giant Exoplanet
Mawet, Dimitri; Hirsch, Lea; Lee, Eve J. et al

in Astronomical Journal (2019), 157

We present the most sensitive direct imaging and radial velocity (RV) exploration of ɛ Eridani to date. ɛ Eridani is an adolescent planetary system, reminiscent of the early solar system. It is surrounded ... [more ▼]

We present the most sensitive direct imaging and radial velocity (RV) exploration of ɛ Eridani to date. ɛ Eridani is an adolescent planetary system, reminiscent of the early solar system. It is surrounded by a prominent and complex debris disk that is likely stirred by one or several gas giant exoplanets. The discovery of the RV signature of a giant exoplanet was announced 15 yr ago, but has met with scrutiny due to possible confusion with stellar noise. We confirm the planet with a new compilation and analysis of precise RV data spanning 30 yr, and combine it with upper limits from our direct imaging search, the most sensitive ever performed. The deep images were taken in the Ms band (4.7 μm) with the vortex coronagraph recently installed in W.M. Keck Observatory’s infrared camera NIRC2, which opens a sensitive window for planet searches around nearby adolescent systems. The RV data and direct imaging upper limit maps were combined in an innovative joint Bayesian analysis, providing new constraints on the mass and orbital parameters of the elusive planet. ɛ Eridani b has a mass of {0.78}[SUB]-0.12[/SUB][SUP]+0.38[/SUP] M [SUB]Jup[/SUB] and is orbiting ɛ Eridani at about 3.48 ± 0.02 au with a period of 7.37 ± 0.07 yr. The eccentricity of ɛ Eridani b’s orbit is {0.07}[SUB]-0.05[/SUB][SUP]+0.06[/SUP], an order of magnitude smaller than early estimates and consistent with a circular orbit. We discuss our findings from the standpoint of planet–disk interactions and prospects for future detection and characterization with the James Webb Space Telescope. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time was granted for this project by Caltech, the University of Hawai’i, the University of California, and NASA. [less ▲]

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See detailReport on HOSTS survey return
Ertel, Steve; Hinz, Phil; Mennesson, Bertrand et al

E-print/Working paper (2019)

Observations for the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey for warm dust around nearby stars (exozodiacal dust, i.e., dust in and near their habitable zones, HZs) have been ... [more ▼]

Observations for the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey for warm dust around nearby stars (exozodiacal dust, i.e., dust in and near their habitable zones, HZs) have been completed in the first half of 2018 (during observing semester 2018A). The goal of HOSTS was to constrain the occurrence rate and typical level of exozodiacal dust around a sample of nearby starsin order to assess the risk imposed by this dust to future space missions attempting to directly image habitable exoplanets. We here report on the immediate conclusions of the survey relevant to this goal.Detailed descriptions of the HOSTS observing strategy, data reduction, and analysis together with detailed statistical results were provided by Ertel et al. (2018a). Here, we provide only a brief summary of these points and updates where necessary. In particular, we provide the final null measurements and derived HZ dust levels (zodi levels) for all observed stars and final statistics derived from those measurements. [less ▲]

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See detailThe LEECH Exoplanet Imaging Survey: Limits on Planet Occurrence Rates under Conservative Assumptions
Stone, Jordan M.; Skemer, Andrew J.; Hinz, Philip M. et al

in Astronomical Journal (2018), 156

We present the results of the largest L‧ (3.8 μm) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars ... [more ▼]

We present the results of the largest L‧ (3.8 μm) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars with spectral types from B to M. Cool planets emit a larger share of their flux in L‧ compared to shorter wavelengths, affording LEECH an advantage in detecting low-mass, old, and cold-start giant planets. We emphasize proximity over youth in our target selection, probing physical separations smaller than other direct imaging surveys. For FGK stars, LEECH outperforms many previous studies, placing tighter constraints on the hot-start planet occurrence frequency interior to ˜20 au. For less luminous, cold-start planets, LEECH provides the best constraints on giant-planet frequency interior to ˜20 au around FGK stars. Direct imaging survey results depend sensitively on both the choice of evolutionary model (e.g., hot- or cold-start) and assumptions (explicit or implicit) about the shape of the underlying planet distribution, in particular its radial extent. Artificially low limits on the planet occurrence frequency can be derived when the shape of the planet distribution is assumed to extend to very large separations, well beyond typical protoplanetary dust-disk radii (≲50 au), and when hot-start models are used exclusively. We place a conservative upper limit on the planet occurrence frequency using cold-start models and planetary population distributions that do not extend beyond typical protoplanetary dust-disk radii. We find that ≲90% of FGK systems can host a 7-10 M [SUB]Jup[/SUB] planet from 5 to 50 au. This limit leaves open the possibility that planets in this range are common. [less ▲]

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See detailSpace-based infrared interferometry to study exoplanetary atmospheres
Defrere, Denis ULiege; Léger, A.; Absil, Olivier ULiege et al

in Experimental Astronomy (2018), 46(3), 543-560

The quest for other habitable worlds and the search for life among them are major goals of modern astronomy. One way to make progress towards these goals is to obtain high-quality spectra of a large ... [more ▼]

The quest for other habitable worlds and the search for life among them are major goals of modern astronomy. One way to make progress towards these goals is to obtain high-quality spectra of a large number of exoplanets over a broad range of wavelengths. While concepts currently investigated in the United States are focused on visible/NIR wavelengths, where the planets are probed in reflected light, a compelling alternative to characterize planetary atmospheres is the mid-infrared waveband (5-20um). Indeed, mid-infrared observations provide key information on the presence of an atmosphere, the surface conditions (e.g., temperature, pressure, habitability), and the atmospheric composition in important species such as H2O, CO2, O3, CH4, and N2O. This information is essential to investigate the potential habitability of exoplanets and to make progress towards the search for life in the universe. Obtaining high-quality mid-infrared spectra of exoplanets from the ground is however extremely challenging due to the overwhelming brightness and turbulence of Earth's atmosphere. In this paper, we present a concept of space-based mid-infrared interferometer that can tackle this observing challenge and discuss the main technological developments required to launch such a sophisticated instrument. [less ▲]

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See detailResults of LBTI’s HOSTS survey and prospects
Defrere, Denis ULiege

Scientific conference (2018, September 21)

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See detailNulling data analysis and how to interpret results
Defrere, Denis ULiege

Scientific conference (2018, September 05)

Review of data analysis for the HOSTS survey

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See detailLBTI nulling data reduction and how to interpret results
Defrere, Denis ULiege

Scientific conference (2018, September 05)

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See detailLBTI: recent results and prospects
Defrere, Denis ULiege

Scientific conference (2018, August 30)

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See detailProspects for the characterisation of exo-zodiacal dust with the VLTI
Ertel, S.; Absil, Olivier ULiege; Defrere, Denis ULiege et al

in Experimental Astronomy (2018), 46(3), 401411

Exo-zodiacal dust, exozodi for short, is warm (∼300 K) or hot (up to ∼2000 K) dust found in the inner regions of planetary systems around main sequence stars. In analogy to our own zodiacal dust, it may ... [more ▼]

Exo-zodiacal dust, exozodi for short, is warm (∼300 K) or hot (up to ∼2000 K) dust found in the inner regions of planetary systems around main sequence stars. In analogy to our own zodiacal dust, it may be located in or near the habitable zone or closer in, down to the dust sublimation distance. The study of the properties, distribution, and evolution of exozodis can inform about the architecture and dynamics of the innermost regions of planetary systems, close to their habitable zones. On the other hand, the presence of large amounts of exo-zodiacal dust may be an obstacle for future space missions aiming to image Earth-like exoplanets. The dust can be the most luminous component of extrasolar planetary systems, but predominantly emits in the near- to mid-infrared where it is outshone by the host star. Interferometry provides a unique method of separating the dusty from the stellar emission. We discuss the prospects of exozodi observations with the next generation VLTI instruments and summarize critical instrument specifications. © 2018, Springer Nature B.V. [less ▲]

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See detailExoplanet science with a space-based mid-infrared nulling interferometer
Quanz, S. P.; Kammerer, J.; Defrere, Denis ULiege et al

in Creech-Eakman, M.; Tuthill, P.; Mérand, A. (Eds.) Optical and Infrared Interferometry and Imaging VI (2018, July 09)

One of the long-term goals of exoplanet science is the (atmospheric) characterization of a large sample (>100) of terrestrial planets to assess their potential habitability and overall diversity. Hence ... [more ▼]

One of the long-term goals of exoplanet science is the (atmospheric) characterization of a large sample (>100) of terrestrial planets to assess their potential habitability and overall diversity. Hence, it is crucial to quantitatively evaluate and compare the scientific return of various mission concepts. Here we discuss the exoplanet yield of a space-based mid-infrared (MIR) nulling interferometer. We use Monte-Carlo simulations, based on the observed planet population statistics from the Kepler mission, to quantify the number and properties of detectable exoplanets (incl. potentially habitable planets) and we compare the results to those for a large aperture optical/NIR space telescope. We investigate how changes in the underlying technical assumptions (sensitivity and spatial resolution) impact the results and discuss scientific aspects that influence the choice for the wavelength coverage and spectral resolution. Finally, we discuss the advantages of detecting exoplanets at MIR wavelengths, summarize the current status of some key technologies, and describe what is needed in terms of further technology development to pave the road for a space-based MIR nulling interferometer for exoplanet science. © 2018 SPIE. [less ▲]

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See detailImage-plane fringe tracker for adaptive-optics assisted long baseline interferometry
Ireland, Michael J.; Defrere, Denis ULiege; Martinache, Frantz et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2018, July 09)

Accurate fringe tracking is essential for sensitive long-wavelength thermal background limited operation of the current Very Large Telescope Interferometry (VLTI) and future Planet Formation Imager (PFI ... [more ▼]

Accurate fringe tracking is essential for sensitive long-wavelength thermal background limited operation of the current Very Large Telescope Interferometry (VLTI) and future Planet Formation Imager (PFI) facilities. We present and simulate a dual fringe tracking and low-order adaptive optics concept based on a combination of non-redundant aperture interferometry and eigenphase in asymmetric pupil wavefront sensing. This scheme can acquire fringes at many wavelengths of path length offset between telescopes, even with moderate tilt offset and pupil shifts between beams. Once locked to fringes, our technique can also be used for simultaneous low-order wavefront sensing, and has near-optimum sensitivity where there is a dominant point-source image component. This concept is part of the Heimdallr visitor instrument currently being investigated for VLTI. [less ▲]

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See detailHi-5: A potential high-contrast thermal near-infrared imager for the VLTI
Defrere, Denis ULiege; Ireland, M.; Absil, Olivier ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, July 09), 10701

Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main ... [more ▼]

Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main-sequence stars. In this paper, we present an update of the project and key technology pathways to improve the contrast achieved by the VLTI. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 μm) and advanced fringe tracking strategies. We also address the strong exoplanet science case (young exoplanets, planet formation, and exozodiacal disks) offered by this wavelength regime as well as other possible science cases such as stellar physics (fundamental parameters and multiplicity) and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed. © 2018 SPIE. [less ▲]

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See detailCharacterizing the atmosphere of Proxima b with a space-based mid-infrared nulling interferometer
Defrere, Denis ULiege; Léger, A.; Absil, Olivier ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, July 09), 10701

Proxima b is our nearest potentially rocky exoplanet and represents a formidable opportunity for exoplanet science and possibly astrobiology. With an angular separation of only 35 mas (or 0.05 AU) from ... [more ▼]

Proxima b is our nearest potentially rocky exoplanet and represents a formidable opportunity for exoplanet science and possibly astrobiology. With an angular separation of only 35 mas (or 0.05 AU) from its host star, Proxima b is however hardly observable with current imaging telescopes and future space-based coronagraphs. One way to separate the photons of the planet from those of its host star is to use an interferometer that can easily resolve such spatial scales. In addition, its proximity to Earth and its favorable contrast ratio compared with its host M dwarf (approximately 10-5 at 10 microns) makes it an ideal target for a space-based nulling interferometer with relatively small apertures. In this paper, we present the motivation for observing this planet in the mid-infrared (5-20 microns) and the corresponding technological challenges. Then, we describe the concept of a space-based infrared interferometer with relatively small (<1m in diameter) apertures that can measure key details of Proxima b, such as its size, temperature, climate structure, as well as the presence of important atmospheric molecules such as H2O, CO2, O3, and CH4. Finally, we illustrate the concept by showing realistic observations using synthetic spectra of Proxima b computed with coupled climate chemistry models. © 2018 SPIE. [less ▲]

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See detailLIFE: Large Interferometer For Exoplanets
Quanz, Sascha; Kammerer, Jens; Defrere, Denis ULiege et al

Poster (2018, July 02)

LIFE is a new project initiated in Europe with the goal to consolidate various efforts and define a roadmap that eventually leads to the launch of a large, space-based MIR nulling interferometer to ... [more ▼]

LIFE is a new project initiated in Europe with the goal to consolidate various efforts and define a roadmap that eventually leads to the launch of a large, space-based MIR nulling interferometer to investigate the atmospheric properties of a large sample of — primarily terrestrial — exoplanets. Centered around clear and ambitious scientific objectives the project will define the relevant science and technical requirements. The status of key technologies will be re-assessed and further technology development will be coordinated. LIFE is based on the heritage of ESA/Darwin and NASA/TPF-I, but significant advances in our understanding of exoplanets and newly available technologies will be taken into account in the LIFE mission concept. One of the long-term objectives of extrasolar planet research is the investigation of the atmospheric properties for a large number (~100) of terrestrial exoplanets. This is partially driven by the idea to search for and identify potential biosignatures, but such a dataset is — in a more general sense — invaluable for understanding the diversity of planetary bodies. While exoplanet science is omnipresent on the roadmaps of all major space agencies and ground-based observatories and first steps in this direction will be taken in the coming 10-15 years, none of the currently selected missions and projects will be able to deliver such a comprehensive dataset. [less ▲]

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See detailThe HOSTS survey for exo-zodiacal dust: preliminary results and future prospects
Ertel, S.; Kennedy, G. M.; Defrere, Denis ULiege et al

in Lystrup, M.; MacEwen; Fazio, G. (Eds.) et al Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave (2018, July 01)

The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed the HOSTS (Hunt for Observable Signatures of ... [more ▼]

The presence of large amounts of dust in the habitable zones of nearby stars is a significant obstacle for future exo-Earth imaging missions. We executed the HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey to determine the typical amount of such exozodiacal dust around a sample of nearby main sequence stars. The majority of the data have been analyzed and we present here an update of our ongoing work. Nulling interferometry in N band was used to suppress the bright stellar light and to detect faint, extended circumstellar dust emission. We present an overview of the latest results from our ongoing work. We find seven new N band excesses in addition to the high confidence confirmation of three that were previously known. We find the first detections around Sun-like stars and around stars without previously known circumstellar dust. Our overall detection rate is 23%. The inferred occurrence rate is comparable for early type and Sun-like stars, but decreases from 71[SUP]+11 -20[/SUP]% for stars with previously detected mid- to far-infrared excess to 11[SUP]+9 -4[/SUP]% for stars without such excess, confirming earlier results at high confidence. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal luminosity function of the dust, we find upper limits on the median dust level around all stars without previously known mid to far infrared excess of 11.5 zodis at 95% confidence level. The corresponding upper limit for Sun-like stars is 16 zodis. An LBTI vetted target list of Sun-like stars for exo-Earth imaging would have a corresponding limit of 7.5 zodis. We provide important new insights into the occurrence rate and typical levels of habitable zone dust around main sequence stars. Exploiting the full range of capabilities of the LBTI provides a critical opportunity for the detailed characterization of a sample of exozodiacal dust disks to understand the origin, distribution, and properties of the dust. [less ▲]

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See detailA two-band approach to nλ phase error corrections with LBTI's PHASECam
Maier, E. R.; Hinz, P. M.; Defrere, Denis ULiege et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2018, July 01)

PHASECam is the Large Binocular Telescope Interferometer's (LBTI) phase sensor, a near-infrared camera which is used to measure tip/tilt and phase variations between the two AO-corrected apertures of the ... [more ▼]

PHASECam is the Large Binocular Telescope Interferometer's (LBTI) phase sensor, a near-infrared camera which is used to measure tip/tilt and phase variations between the two AO-corrected apertures of the Large Binocular Telescope (LBT). Tip/tilt and phase sensing are currently performed in the H (1.65 μm) and K (2.2 μm) bands at 1 kHz, and the K band phase telemetry is used to send tip/tilt and Optical Path Difference (OPD) corrections to the system. However, phase variations outside the range [-Π, Π] are not sensed, and thus are not fully corrected during closed-loop operation. PHASECam's phase unwrapping algorithm, which attempts to mitigate this issue, still occasionally fails in the case of fast, large phase variations. This can cause a fringe jump, in which case the unwrapped phase will be incorrect by a wavelength or more. This can currently be manually corrected by the observer, but this is inefficient. A more reliable and automated solution is desired, especially as the LBTI begins to commission further modes which require robust, active phase control, including controlled multi-axial (Fizeau) interferometry and dual-aperture non-redundant aperture masking interferometry. We present a multi-wavelength method of fringe jump capture and correction which involves direct comparison between the K band and currently unused H band phase telemetry. [less ▲]

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See detailPlanet formation imager: Project update
Monnier, J. D.; Ireland, M.; Kraus, S. et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, July 01), 10701

The Planet Formation Imager (PFI) is a near- and mid-infrared interferometer project with the driving science goal of imaging directly the key stages of planet formation, including the young proto-planets ... [more ▼]

The Planet Formation Imager (PFI) is a near- and mid-infrared interferometer project with the driving science goal of imaging directly the key stages of planet formation, including the young proto-planets themselves. Here, we will present an update on the work of the Science Working Group (SWG), including new simulations of dust structures during the assembly phase of planet formation and quantitative detection efficiencies for accreting and non-accreting young exoplanets as a function of mass and age. We use these results to motivate two reference PFI designs consisting of a) twelve 3m telescopes with a maximum baseline of 1.2km focused on young exoplanet imaging and b) twelve 8m telescopes optimized for a wider range of young exoplanets and protoplanetary disk imaging out to the 150K H2O ice line. Armed with 4 x 8m telescopes, the ESO/VLTI can already detect young exoplanets in principle and projects such as MATISSE, Hi-5 and Heimdallr are important PFI pathfinders to make this possible. We also discuss the state of technology development needed to make PFI more affordable, including progress towards new designs for inexpensive, small field-of-view, large aperture telescopes and prospects for Cubesat-based space interferometry. © 2018 SPIE. [less ▲]

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See detailThe path towards high-contrast imaging with the VLTI: the Hi-5 project
Defrere, Denis ULiege; Absil, Olivier ULiege; Berger, J.-P. et al

in Experimental Astronomy (2018), 1801

The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI. As of today, the VLTI routinely achieves contrasts of a few 10$^{-3}$ in the near-infrared ... [more ▼]

The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI. As of today, the VLTI routinely achieves contrasts of a few 10$^{-3}$ in the near-infrared with PIONIER (H band) and GRAVITY (K band). Nulling interferometers in the northern hemisphere and non-redundant aperture masking experiments have, however, demonstrated that contrasts of at least a few 10$^{-4}$ are within reach using specific beam combination and data acquisition techniques. In this paper, we explore the possibility to reach similar or higher contrasts on the VLTI. After reviewing the state-of-the-art in high-contrast infrared interferometry, we discuss key features that made the success of other high-contrast interferometric instruments (e.g., integrated optics, nulling, closure phase, and statistical data reduction) and address possible avenues to improve the contrast of the VLTI by at least one order of magnitude. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 $\mu$m), a sweet spot to image and characterize young extra-solar planetary systems. Finally, we address the science cases of a high-contrast VLTI imaging instrument and focus particularly on exoplanet science (young exoplanets, planet formation, and exozodiacal disks), stellar physics (fundamental parameters and multiplicity), and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed. [less ▲]

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See detailCharacterizing exoplanets with infrared interferometry
Defrere, Denis ULiege

Scientific conference (2018, June 04)

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