References of "Defrere, Denis"
     in
Bookmark and Share    
Full Text
See detailUnveiling new stellar companions from the EXOZODI survey : follow up
Marion, Lindsay ULg; Absil, Olivier ULg; Ertel, Steve et al

Poster (2016, June 30)

In 2012, we have conducted a survey of nearby main sequence stars with VLTI/PIONIER to search for the presence of circumstellar dust. We focused on the use of the closure phases and the square ... [more ▼]

In 2012, we have conducted a survey of nearby main sequence stars with VLTI/PIONIER to search for the presence of circumstellar dust. We focused on the use of the closure phases and the square visibilities in a combined way to search for faint companions around the whole sample. In this process, we found four new stellar companions, for which we conducted follow-up observations in 2014. This follow up allows us to confirm the four detections, and to detect another new companion. Only the case of HD202730 remains ambiguous. [less ▲]

Detailed reference viewed: 11 (1 ULg)
Full Text
See detailVortex Image Processing (VIP) package for high-contrast direct imaging
Gómez González, Carlos ULg; Absil, Olivier ULg; Wertz, Olivier ULg et al

Poster (2016, May 16)

VIP is a Python instrument-agnostic toolbox featuring a flexible framework for reproducible and robust data reduction. VIP currently supports three high-contrast imaging observational techniques: angular ... [more ▼]

VIP is a Python instrument-agnostic toolbox featuring a flexible framework for reproducible and robust data reduction. VIP currently supports three high-contrast imaging observational techniques: angular, reference-star and multi-spectral differential imaging. The code can be downloaded from our git repository on Github: http://github.com/vortex-exoplanet/VIP [less ▲]

Detailed reference viewed: 35 (3 ULg)
Full Text
Peer Reviewed
See detailModels of the η Corvi Debris Disk from the Keck Interferometer, Spitzer, and Herschel
Lebreton, J.; Beichman, C.; Bryden, G. et al

in Astrophysical Journal (2016), 817

Debris disks are signposts of analogs to small-body populations of the solar system, often, however, with much higher masses and dust production rates. The disk associated with the nearby star η Crv is ... [more ▼]

Debris disks are signposts of analogs to small-body populations of the solar system, often, however, with much higher masses and dust production rates. The disk associated with the nearby star η Crv is especially striking, as it shows strong mid- and far-infrared excesses despite an age of ∼1.4 Gyr. We undertake constructing a consistent model of the system that can explain a diverse collection of spatial and spectral data. We analyze Keck Interferometer Nuller measurements and revisit Spitzer and additional spectrophotometric data, as well as resolved Herschel images, to determine the dust spatial distribution in the inner exozodi and in the outer belt. We model in detail the two-component disk and the dust properties from the sub-AU scale to the outermost regions by fitting simultaneously all measurements against a large parameter space. The properties of the cold belt are consistent with a collisional cascade in a reservoir of ice-free planetesimals at 133 AU. It shows marginal evidence for asymmetries along the major axis. KIN enables us to establish that the warm dust consists of a ring that peaks between 0.2 and 0.8 AU. To reconcile this location with the ∼400 K dust temperature, very high albedo dust must be invoked, and a distribution of forsterite grains starting from micron sizes satisfies this criterion, while providing an excellent fit to the spectrum. We discuss additional constraints from the LBTI and near-infrared spectra, and we present predictions of what James Webb Space Telescope can unveil about this unusual object and whether it can detect unseen planets. [less ▲]

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailThe LEECH Exoplanet Imaging Survey: Orbit and Component Masses of the Intermediate-age, Late-type Binary NO UMa
Schlieder, Joshua E.; Skemer, Andrew J.; Maire, Anne-Lise et al

in Astrophysical Journal (2016), 818

We present high-resolution Large Binocular Telescope LBTI/LMIRcam images of the spectroscopic and astrometric binary NO UMa obtained as part of the LBT Interferometer Exozodi Exoplanet Common Hunt ... [more ▼]

We present high-resolution Large Binocular Telescope LBTI/LMIRcam images of the spectroscopic and astrometric binary NO UMa obtained as part of the LBT Interferometer Exozodi Exoplanet Common Hunt exoplanet imaging survey. Our H-, K[SUB]s[/SUB]-, and L‧-band observations resolve the system at angular separations <0.″09. The components exhibit significant orbital motion over a span of ∼7 months. We combine our imaging data with archival images, published speckle interferometry measurements, and existing spectroscopic velocity data to solve the full orbital solution and estimate component masses. The masses of the K2.0 ± 0.5 primary and K6.5 ± 0.5 secondary are 0.83 ± 0.02 M[SUB]⊙[/SUB] and 0.64 ± 0.02 M[SUB]⊙[/SUB], respectively. We also derive a system distance of d = 25.87 ± 0.02 pc and revise the Galactic kinematics of NO UMa. Our revised Galactic kinematics confirm NO UMa as a nuclear member of the ∼500 Myr old Ursa Major moving group, and it is thus a mass and age benchmark. We compare the masses of the NO UMa binary components to those predicted by five sets of stellar evolution models at the age of the Ursa Major group. We find excellent agreement between our measured masses and model predictions with little systematic scatter between the models. NO UMa joins the short list of nearby, bright, late-type binaries having known ages and fully characterized orbits. Based on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC. [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailThe Inner Debris Structure in the Fomalhaut Planetary System
Su, Kate Y. L.; Rieke, George H.; Defrere, Denis ULg et al

in Astrophysical Journal (2016), 818

Fomalhaut plays an important role in the study of debris disks and small bodies in other planetary systems. The proximity and luminosity of the star make key features of its debris, like the water ice ... [more ▼]

Fomalhaut plays an important role in the study of debris disks and small bodies in other planetary systems. The proximity and luminosity of the star make key features of its debris, like the water ice line, accessible. Here we present ALMA cycle 1, 870 μm (345 GHz) observations targeted at the inner part of the Fomalhaut system with a synthesized beam of 0.″45 × 0.″37 (˜3 AU linear resolution at the distance of Fomalhaut) and an rms of 26 μJy beam[SUP]-1[/SUP]. The high angular resolution and sensitivity of the ALMA data enable us to place strong constraints on the nature of the warm excess revealed by Spitzer and Herschel observations. We detect a point source at the star position with a total flux consistent with thermal emission from the stellar photosphere. No structures that are brighter than 3σ are detected in the central 15 AU × 15 AU region. Modeling the spectral energy distribution using parameters expected for a dust-producing planetesimal belt indicates a radial location in the range of ˜8-15 AU. This is consistent with the location where ice sublimates in Fomalhaut, i.e., an asteroid-belt analog. The 3σ upper limit for such a belt is <1.3 mJy at 870 μm. We also interpret the 2 and 8-13 μm interferometric measurements to reveal the structure in the inner 10 AU region as dust naturally connected to this proposed asteroid belt by Poynting-Robertson drag, dust sublimation, and magnetically trapped nanograins. Fomalhaut is a triple system; here we refer to the Fomalhaut planetary system as the one around the primary star Fomalhaut A. [less ▲]

Detailed reference viewed: 24 (1 ULg)
Full Text
Peer Reviewed
See detailThe LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Superstellar Metallicity
Skemer, Andrew J.; Morley, Caroline V.; Zimmerman, Neil T. et al

in Astrophysical Journal (2016), 817

As gas giant planets and brown dwarfs radiate away the residual heat from their formation, they cool through a spectral type transition from L to T, which encompasses the dissipation of cloud opacity and ... [more ▼]

As gas giant planets and brown dwarfs radiate away the residual heat from their formation, they cool through a spectral type transition from L to T, which encompasses the dissipation of cloud opacity and the appearance of strong methane absorption. While there are hundreds of known T-type brown dwarfs, the first generation of directly imaged exoplanets were all L type. Recently, Kuzuhara et al. announced the discovery of GJ 504 b, the first T dwarf exoplanet. GJ 504 b provides a unique opportunity to study the atmosphere of a new type of exoplanet with a ˜500 K temperature that bridges the gap between the first directly imaged planets (˜1000 K) and our own solar system's Jupiter (˜130 K). We observed GJ 504 b in three narrow L-band filters (3.71, 3.88, and 4.00 μm), spanning the red end of the broad methane fundamental absorption feature (3.3 μm) as part of the LBTI Exozodi Exoplanet Common Hunt (LEECH) exoplanet imaging survey. By comparing our new photometry and literature photometry with a grid of custom model atmospheres, we were able to fit GJ 504 b's unusual spectral energy distribution for the first time. We find that GJ 504 b is well fit by models with the following parameters: T[SUB]eff[/SUB] = 544 ± 10 K, g < 600 m s[SUP]-2[/SUP], [M/H] = 0.60 ± 0.12, cloud opacity parameter of f[SUB]sed[/SUB] = 2-5, R = 0.96 ± 0.07 R[SUB]Jup[/SUB], and log(L) = -6.13 ± 0.03 L[SUB]⊙[/SUB], implying a hot start mass of 3-30 M[SUB]jup[/SUB] for a conservative age range of 0.1-6.5 Gyr. Of particular interest, our model fits suggest that GJ 504 b has a superstellar metallicity. Since planet formation can create objects with nonstellar metallicities, while binary star formation cannot, this result suggests that GJ 504 b formed like a planet, not like a binary companion. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrophisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia. [less ▲]

Detailed reference viewed: 25 (1 ULg)
See detailTwo Small Temperate Planets Transiting Nearby M Dwarfs in K2 Campaigns 0 and 1
Schlieder, Joshua E.; Crossfield, Ian J. M.; Petigura, Erik A. et al

in Astrophysical Journal (2016), 818

The prime Kepler mission revealed that small planets (<4 {R}[SUB]\oplus [/SUB]) are common, especially around low-mass M dwarfs. K2, the repurposed Kepler mission, continues this exploration of small ... [more ▼]

The prime Kepler mission revealed that small planets (<4 {R}[SUB]\oplus [/SUB]) are common, especially around low-mass M dwarfs. K2, the repurposed Kepler mission, continues this exploration of small planets around small stars. Here we combine K2 photometry with spectroscopy, adaptive optics imaging, and archival survey images to analyze two small planets orbiting the nearby field-age M dwarfs, K2-26 (EPIC 202083828) and K2-9. K2-26 is an {{M}}1.0+/- 0.5 dwarf at 93 ± 7 pc from K2 Campaign 0. We validate its planet with a day period of 14.5665 and estimate a radius of {2.67}[SUB]-0.42[/SUB][SUP]+0.46[/SUP] {R}[SUB]\oplus [/SUB]. K2-9 is an {{M}}2.5+/- 0.5 dwarf at 110 ± 12 pc from K2 Campaign 1. K2-9b was first identified by Montet et al.; here we present spectra and adaptive optics imaging of the host star and independently validate and characterize the planet. Our analyses indicate K2-9b is a {2.25}[SUB]-0.96[/SUB][SUP]+0.53[/SUP] {R}[SUB]\oplus [/SUB] planet with a 18.4498 day period. K2-26b exhibits a transit duration that is too long to be consistent with a circular orbit given its measured stellar radius. Thus, the long transits are likely due to the photoeccentric effect and our transit fits hint at an eccentric orbit. Both planets receive low incident flux from their host stars and have estimated equilibrium temperatures <500 K. K2-9b may receive approximately Earth-like insolation. However, its host star exhibits strong GALEX UV emission which could affect any atmosphere it harbors. K2-26b and K2-9b are representatives of a poorly studied class of small planets with cool temperatures that have radii intermediate to Earth and Neptune. Future study of these systems can provide key insight into trends in bulk composition and atmospheric properties at the transition from silicate dominated to volatile rich bodies. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, La Silla Observatory, Chile during program ID 194.C-0443. [less ▲]

Detailed reference viewed: 14 (2 ULg)
See detailAn Accreting Protoplanet: Confirmation and Characterization of LkCa15b
Follette, Katherine B.; Miller Close, Laird; Males, Jared et al

in American Astronomical Society Meeting Abstracts (2016, January 01)

We present a visible light adaptive optics direct imaging detection of a faint point source separated by just 93 milliarcseconds (~15 AU) from the young star LkCa 15. Using Magellan AO's visible light ... [more ▼]

We present a visible light adaptive optics direct imaging detection of a faint point source separated by just 93 milliarcseconds (~15 AU) from the young star LkCa 15. Using Magellan AO's visible light camera in Simultaneous Differential Imaging (SDI) mode, we imaged the star at Hydrogen alpha and in the neighboring continuum as part of the Giant Accreting Protoplanet Survey (GAPplanetS) in November 2015. The continuum images provide a sensitive and simultaneous probe of PSF residuals and instrumental artifacts, allowing us to isolate H-alpha accretion luminosity from the LkCa 15b protoplanet, which lies well inside of the LkCa15 transition disk gap. This detection, combined with a nearly simultaneous near-infrared detection with the Large Binocular Telescope, provides an unprecedented glimpse at a planetary system during epoch of planet formation. [less ▲]

Detailed reference viewed: 11 (1 ULg)
See detailDoes Fomalhaut A Have an Asteroid-belt Analog?
Su, Kate Y. L.; Rieke, George; Defrere, Denis ULg et al

in American Astronomical Society Meeting Abstracts (2016, January 01)

Fomalhaut plays an important role in the study of debris disks and small bodies in other planetary systems. The proximity and luminosity of the star make key features of its debris like the water ice-line ... [more ▼]

Fomalhaut plays an important role in the study of debris disks and small bodies in other planetary systems. The proximity and luminosity of the star make key features of its debris like the water ice-line easily accessible. Here we present ALMA cycle 1, 870 μm (345 GHz) observation targeted at the inner part of the Fomalhaut system with a synthesized beam of 0.45"x0.37" (~3 AU linear resolution at the distance of Fomalhaut) and a rms of 26 μJy per beam. The high angular resolution and sensitivity of the ALMA data enable us to place strong constraints on the nature of the warm excess revealed by Spitzer and Herschel observations. We detect a point source at the star position with a total flux consistent with thermal emission from the stellar photosphere. No structures that are brighter than 3 σ are detected in the central 15 AUx15 AU region. Modeling the spectral energy distribution using parameters expected for a dust-producing planetesimal belt indicates a radial location in the range ˜8-15 AU. This is consistent with the location where ice sublimates in Fomalhaut, i.e., an asteroid-belt analog. We also provide a new interpretation for the emission structure in the inner 10 AU region revealed by interferometric measurements at 2 and 8-13 μm as dust naturally connected to this proposed asteroid belt by Poynting-Robertson drag, dust sublimation, and magnetically trapped nano grains. [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
Peer Reviewed
See detailAccreting protoplanets in the LkCa 15 transition disk
Sallum, S.; Follette, K. B.; Eisner, J. A. et al

in Nature (2015), 527

Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1,900 exoplanets have now been discovered and confirmed, none ... [more ▼]

Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1,900 exoplanets have now been discovered and confirmed, none are still in the process of formation. Transition disks, protoplanetary disks with inner clearings best explained by the influence of accreting planets, are natural laboratories for the study of planet formation. Some transition disks show evidence for the presence of young planets in the form of disk asymmetries or infrared sources detected within their clearings, as in the case of LkCa 15 (refs 8, 9). Attempts to observe directly signatures of accretion onto protoplanets have hitherto proven unsuccessful. Here we report adaptive optics observations of LkCa 15 that probe within the disk clearing. With accurate source positions over multiple epochs spanning 2009-2015, we infer the presence of multiple companions on Keplerian orbits. We directly detect Hα emission from the innermost companion, LkCa 15 b, evincing hot (about 10,000 kelvin) gas falling deep into the potential well of an accreting protoplanet. [less ▲]

Detailed reference viewed: 10 (1 ULg)
Full Text
See detailHunting for Planets in the HL Tau Disk
Testi, L.; Skemer, A.; Henning, Th et al

in Astrophysical Journal Letters (2015), 812

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet ... [more ▼]

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably in a gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in the L‧ band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominent dips in the dust distribution at ˜70 AU (˜0.″5) from the central star, we reach a contrast level of ˜7.5 mag. We did not detect any point sources at the location of the rings. Using evolutionary models we derive upper limits of ˜10-15 M[SUB]Jup[/SUB] at ≤0.5-1 Ma for the possible planets. With these sensitivity limits we should have been able to detect companions sufficiently massive to open full gaps in the disk. The structures detected at millimeter wavelengths could be gaps in the distributions of large grains on the disk midplane caused by planets not massive enough to fully open the gaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infrared observations may be able to provide a definitive answer. [less ▲]

Detailed reference viewed: 11 (1 ULg)
Full Text
Peer Reviewed
See detailThe LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system (Corrigendum)
Maire, A.-L.; Skemer, A. J.; Hinz, P. M. et al

in Astronomy and Astrophysics (2015), 579

The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system ... [more ▼]

The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. [less ▲]

Detailed reference viewed: 14 (2 ULg)
Full Text
Peer Reviewed
See detailSpatially Resolved M-band Emission from Io's Loki Patera-Fizeau Imaging at the 22.8 m LBT
Conrad, Albert; de Kleer, Katherine; Leisenring, Jarron et al

in Astronomical Journal (2015), 149

The Large Binocular Telescope Interferometer mid-infrared camera, LMIRcam, imaged Io on the night of 2013 December 24 UT and detected strong M-band (4.8 μm) thermal emission arising from Loki Patera. The ... [more ▼]

The Large Binocular Telescope Interferometer mid-infrared camera, LMIRcam, imaged Io on the night of 2013 December 24 UT and detected strong M-band (4.8 μm) thermal emission arising from Loki Patera. The 22.8 m baseline of the Large Binocular Telescope provides an angular resolution of ˜32 mas (˜100 km at Io) resolving the Loki Patera emission into two distinct maxima originating from different regions within Loki’s horseshoe lava lake. This observation is consistent with the presence of a high-temperature source observed in previous studies combined with an independent peak arising from cooling crust from recent resurfacing. The deconvolved images also reveal 15 other emission sites on the visible hemisphere of Io including two previously unidentified hot spots. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailThe LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system
Maire, A.-L.; Skemer, A. J.; Hinz, P. M. et al

in Astronomy and Astrophysics (2015), 576

Context. Astrometric monitoring of directly imaged exoplanets allows the study of their orbital parameters and system architectures. Because most directly imaged planets have long orbital periods (>20 AU ... [more ▼]

Context. Astrometric monitoring of directly imaged exoplanets allows the study of their orbital parameters and system architectures. Because most directly imaged planets have long orbital periods (>20 AU), accurate astrometry is challenging when based on data acquired on timescales of a few years and usually with different instruments. The LMIRCam camera on the Large Binocular Telescope is being used for the LBT Exozodi Exoplanet Common Hunt (LEECH) survey to search for and characterize young and adolescent exoplanets in L' band (3.8 μm), including their system architectures. <BR /> Aims: We first aim to provide a good astrometric calibration of LMIRCam. Then, we derive new astrometry, test the predictions of the orbital model of 8:4:2:1 mean motion resonance proposed for the system, and perform new orbital fitting of the HR 8799 bcde planets. We also present deep limits on a putative fifth planet inside the known planets. <BR /> Methods: We use observations of HR 8799 and the Θ[SUP]1[/SUP] Ori C field obtained during the same run in October 2013. <BR /> Results: We first characterize the distortion of LMIRCam. We determine a platescale and a true north orientation for the images of 10.707 ± 0.012 mas/pix and -0.430 ± 0.076°, respectively. The errors on the platescale and true north orientation translate into astrometric accuracies at a separation of 1'' of 1.1 mas and 1.3 mas, respectively. The measurements for all planets agree within 3σ with a predicted ephemeris. The orbital fitting based on the new astrometric measurements favors an architecture for the planetary system based on 8:4:2:1 mean motion resonance. The detection limits allow us to exclude a fifth planet slightly brighter or more massive than HR 8799 b at the location of the 2:1 resonance with HR 8799 e (~9.5 AU) and about twice as bright as HR 8799 cde at the location of the 3:1 resonance with HR 8799 e (~7.5 AU). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. [less ▲]

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailTarget Selection for the LBTI Exozodi Key Science Program
Weinberger, Alycia J.; Bryden, Geoff; Kennedy, Grant M. et al

in Astrophysical Journal Supplement Series (2015), 216

The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) on the Large Binocular Telescope Interferometer will survey nearby stars for faint emission arising from ~300 K dust ... [more ▼]

The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) on the Large Binocular Telescope Interferometer will survey nearby stars for faint emission arising from ~300 K dust (exozodiacal dust), and aims to determine the exozodiacal dust luminosity function. HOSTS results will enable planning for future space telescopes aimed at direct spectroscopy of habitable zone terrestrial planets, as well as greater understanding of the evolution of exozodiacal disks and planetary systems. We lay out here the considerations that lead to the final HOSTS target list. Our target selection strategy maximizes the ability of the survey to constrain the exozodi luminosity function by selecting a combination of stars selected for suitability as targets of future missions and as sensitive exozodi probes. With a survey of approximately 50 stars, we show that HOSTS can enable an understanding of the statistical distribution of warm dust around various types of stars and is robust to the effects of varying levels of survey sensitivity induced by weather conditions. [less ▲]

Detailed reference viewed: 6 (1 ULg)
Full Text
Peer Reviewed
See detailExo-zodi Modeling for the Large Binocular Telescope Interferometer
Kennedy, Grant M.; Wyatt, Mark C.; Bailey, Vanessa et al

in The Astrophysical Journal Supplement Series (2015), 216

Habitable zone dust levels are a key unknown that must be understood to ensure the success of future space missions to image Earth analogs around nearby stars. Current detection limits are several orders ... [more ▼]

Habitable zone dust levels are a key unknown that must be understood to ensure the success of future space missions to image Earth analogs around nearby stars. Current detection limits are several orders of magnitude above the level of the solar system's zodiacal cloud, so characterization of the brightness distribution of exo-zodi down to much fainter levels is needed. To this end, the Large Binocular Telescope Interferometer (LBTI) will detect thermal emission from habitable zone exo-zodi a few times brighter than solar system levels. Here we present a modeling framework for interpreting LBTI observations, which yields dust levels from detections and upper limits that are then converted into predictions and upper limits for the scattered light surface brightness. We apply this model to the HOSTS survey sample of nearby stars; assuming a null depth uncertainty of 10[SUP]-4[/SUP] the LBTI will be sensitive to dust a few times above the solar system level around Sun-like stars, and to even lower dust levels for more massive stars. [less ▲]

Detailed reference viewed: 14 (1 ULg)
Full Text
Peer Reviewed
See detailDoes the Debris Disk around HD 32297 Contain Cometary Grains?
Rodigas, Timothy J.; Debes, John H.; Hinz, Philip M. et al

in Astrophysical Journal (2014), 783

We present an adaptive optics imaging detection of the HD 32297 debris disk at L' (3.8 μm) obtained with the LBTI/LMIRcam infrared instrument at the Large Binocular Telescope. The disk is detected at ... [more ▼]

We present an adaptive optics imaging detection of the HD 32297 debris disk at L' (3.8 μm) obtained with the LBTI/LMIRcam infrared instrument at the Large Binocular Telescope. The disk is detected at signal-to-noise ratio per resolution element ~3-7.5 from ~0.''3 to 1.''1 (30-120 AU). The disk at L' is bowed, as was seen at shorter wavelengths. This likely indicates that the disk is not perfectly edge-on and contains highly forward-scattering grains. Interior to ~50 AU, the surface brightness at L' rises sharply on both sides of the disk, which was also previously seen at Ks band. This evidence together points to the disk containing a second inner component located at lsim50 AU. Comparing the color of the outer (50 <r/AU <120) portion of the disk at L' with archival Hubble Space Telescope/NICMOS images of the disk at 1-2 μm allows us to test the recently proposed cometary grains model of Donaldson et al. We find that the model fails to match this disk's surface brightness and spectrum simultaneously (reduced chi-square = 17.9). When we modify the density distribution of the model disk, we obtain a better overall fit (reduced chi-square = 2.87). The best fit to all of the data is a pure water ice model (reduced chi-square = 1.06), but additional resolved imaging at 3.1 μm is necessary to constrain how much (if any) water ice exists in the disk, which can then help refine the originally proposed cometary grains model. Based on observations made at the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: the University of Arizona on behalf of the Arizona University system; Istituto Nazionale di Astrosica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota and University of Virginia. Based on observations made using the Large Binocular Telescope Interferometer (LBTI). LBTI is funded by the National Aeronautics and Space Administration as part of its Exoplanet Exploration program. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
See detailCharacterization of the Benchmark Binary NLTT 33370
Schlieder, Joshua E.; Bonnefoy, Mickaël; Herbst, T. M. et al

in Astrophysical Journal (2014), 783

We confirm the binary nature of the nearby, very low mass (VLM) system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared ... [more ▼]

We confirm the binary nature of the nearby, very low mass (VLM) system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show significant orbital motion between 2013 February and 2013 April. Optical spectra reveal weak, gravity-sensitive alkali lines and strong lithium 6708 Å absorption that indicate the system is younger than field age. VLT-SINFONI near-IR spectra also show weak, gravity-sensitive features and spectral morphology that is consistent with other young VLM dwarfs. We combine the constraints from all age diagnostics to estimate a system age of ~30-200 Myr. The 1.2-4.7 μm spectral energy distribution of the components point toward T [SUB]eff[/SUB] = 3200 ± 500 K and T [SUB]eff[/SUB] = 3100 ± 500 K for NLTT 33370 A and B, respectively. The observed spectra, derived temperatures, and estimated age combine to constrain the component spectral types to the range M6-M8. Evolutionary models predict masses of 97^{+41}_{-48}\,M_{Jup} and 91^{+41}_{-44}\,M_{Jup} from the estimated luminosities of the components. KPNO-Phoenix spectra allow us to estimate the systemic radial velocity of the binary. The Galactic kinematics of NLTT 33370AB are broadly consistent with other young stars in the solar neighborhood. However, definitive membership in a young, kinematic group cannot be assigned at this time and further follow-up observations are necessary to fully constrain the system's kinematics. The proximity, age, and late-spectral type of this binary make it very novel and an ideal target for rapid, complete orbit determination. The system is one of only a few model calibration benchmarks at young ages and VLMs. [less ▲]

Detailed reference viewed: 15 (1 ULg)
Full Text
Peer Reviewed
See detailMid-infrared High-contrast Imaging of HD 114174 B: An Apparent Age Discrepancy in a "Sirius-like" Binary System
Matthews, Christopher T.; Crepp, Justin R.; Skemer, Andrew et al

in Astrophysical Journal Letters (2014), 783

We present new observations of the faint "Sirius-like" companion discovered to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared wavelengths using NIRC2 at Keck have resulted in a ... [more ▼]

We present new observations of the faint "Sirius-like" companion discovered to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared wavelengths using NIRC2 at Keck have resulted in a non-detection. Our new L'-band observations taken with the Large Binocular Telescope and L/M-band InfraRed Camera recover the companion (ΔL = 10.15 ± 0.15 mag, ρ = 0.''675 ± 0.''016) with a high signal-to-noise ratio (10σ). This measurement represents the deepest L' high-contrast imaging detection at subarcsecond separations to date, including extrasolar planets. We confirm that HD 114174 B has near-infrared colors consistent with the interpretation of a cool white dwarf (WD; J - L' = 0.76 ± 0.19 mag, K - L' = 0.64 ± 0.20). New model fits to the object's spectral energy distribution indicate a temperature T [SUB]eff[/SUB] = 4260 ± 360 K, surface gravity log g = 7.94 ± 0.03, a cooling age t[SUB]c[/SUB] ≈ 7.8 Gyr, and mass M = 0.54 ± 0.01 M [SUB]⊙[/SUB]. We find that the cooling ages given by theoretical atmospheric models do not agree with the age of HD 114174 A derived from both isochronological and gyrochronological analyses. We speculate on possible scenarios to explain the apparent age discrepancy between the primary and secondary. HD 114174 B is a nearby benchmark WD that will ultimately enable a dynamical mass estimate through continued Doppler and astrometric monitoring. Efforts to characterize its physical properties in detail will test theoretical atmospheric models and improve our understanding of WD evolution, cooling, and progenitor masses. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailCharacterization of the gaseous companion κ Andromedae b. New Keck and LBTI high-contrast observations
Bonnefoy, M.; Currie, T.; Marleau, G.-D. et al

in Astronomy and Astrophysics (2014), 562

Context. We previously reported the direct detection of a low-mass companion at a projected separation of 55 ± 2 AU around the B9-type star κ Andromedae. The properties of the system (mass ratio ... [more ▼]

Context. We previously reported the direct detection of a low-mass companion at a projected separation of 55 ± 2 AU around the B9-type star κ Andromedae. The properties of the system (mass ratio, separation) make it a benchmark for understanding the formation and evolution of gas giant planets and brown dwarfs on wide orbits. <BR /> Aims: We present new angular differential imaging (ADI) images of the system at 2.146 (K[SUB]s[/SUB]), 3.776 (L'), 4.052 (NB_4.05), and 4.78 μm (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We aim to determine the near-infrared spectral energy distribution of the companion and use it to characterize the object. <BR /> Methods: We used analysis methods adapted to ADI to extract the companion flux. We compared the photometry of the object to reference young, and old objects and to a set of seven PHOENIX-based atmospheric models of cool objects accounting for the formation of dust. We used evolutionary models to derive mass estimates considering a wide range of plausible initial conditions. Finally, we used dedicated formation models to discuss the possible origin of the companion. <BR /> Results: We derive a more accurate J = 15.86 ± 0.21, H = 14.95 ± 0.13, K[SUB]s[/SUB] = 14.32 ± 0.09 mag for κ And b. We detect the companion in all our high-contrast observations. We confirm previous contrasts obtained at K[SUB]s[/SUB] and L' band. We derive NB_4.05 = 13.0 ± 0.2, and M' = 13.3 ± 0.3 mag and estimate log [SUB]10[/SUB](L/L[SUB]⊙[/SUB]) = -3.76 ± 0.06. Atmospheric models yield T[SUB]eff[/SUB] = 1900[SUP]+100[/SUP][SUB]-200[/SUB] K. They do not set any constraint on the surface gravity. "Hot-start" evolutionary models predict masses of 14[SUP]+25[/SUP][SUB]-2[/SUB] M[SUB]Jup[/SUB] based on the luminosity and temperature estimates, and when considering a conservative age range for the system (30[SUP]+120[/SUP][SUB]-10[/SUB] Myr), "warm-start" evolutionary tracks constrain the mass to M ≥ 10M[SUB]Jup[/SUB]. <BR /> Conclusions: The mass of κ Andromedae b mostly falls in the brown-dwarf regime, owing to remaining uncertainties in age and in mass-luminosity models. According to the formation models, disk instability in a primordial disk may account for the position and a wide range of plausible masses of κ And b. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Instituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.Appendices are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201322119/olm">http://www.aanda.org</A> [less ▲]

Detailed reference viewed: 6 (1 ULg)