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Sökning: WFRF:(Guyon Olivier) > Guyon Olivier

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1.
  • Kaeufl, Hans Ulrich, et al. (författare)
  • NEAR : New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)
  • 2018
  • Ingår i: Ground-Based And Airborne Instrumentation For Astronomy VII. - : SPIE. - 9781510619586
  • Konferensbidrag (refereegranskat)abstract
    • ESO in collaboration with the Breakthrough Initiatives, is adding a dedicated coronagraph to the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability of this instrument. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope, even at wavelengths as long as 10 mu m, critically needs adaptive optics. For VISIR, a work-horse observatory facility instrument in normal operations, this is "easiest" achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This "visit" enables a meaningful search for Earth-like planets in the habitable zone around both alpha-Cen(1) and alpha-Cen(2). Meaningful here means, achieving a contrast of approximate to 10(-6) within approximate to 0.8 arcsec from the star. Various measures to improve the sensitivity of VISIR will be applied, especially a dedicated filter, faster chopping and a Strehl-ratio close to 100% thanks to extreme adaptive optics. This should allow to detect a planet twice the diameter of Earth in 50 h on source integration time. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K microwave background. For risk mitigation all components are being tested and quali fi ed under realistic conditions in the lab at ESO headquarters before integration into the instrument. The performance or suppression of the coronagraph is so good, that a non-thermal source (vulgo a laser) is needed on the test-bench. We will give an overview of the optical changes to VISIR, the implementation of wave front sensing, the Dicke switch design and laboratory testing, the AGPM design and laboratory testing, non common path error control with a ZELDA mask, sensitivity and contrast estimates, data flow and analysis, the overall project status, plan and outlook Needless to say that this project is of critical interest for future infrared instrumentation at the next generation of extremely large telescopes aiming at surveying the solar neighborhood for terrestrial planets by detecting and characterizing them based on their mid-IR fluxes.
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2.
  • Skaf, Nour, et al. (författare)
  • The β Pictoris system : Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR
  • 2023
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 675
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. β Pictoris is a young nearby system hosting a well-resolved edge-on debris disk, along with at least two exoplanets. It offers key opportunities for carrying out detailed studies of the evolution of young planetary systems and their shaping soon after the end of the planetary formation phase. Aims. We analyzed high-contrast coronagraphic images of this system, obtained in the mid-infrared, taking advantage of the NEAR experiment using the VLT/VISIR instrument, which provides access to adaptive optics, as well as phase coronagraphy. The goal of our analysis is to investigate both the detection of the planet β Pictoris b and of the disk features at mid-IR wavelengths. In addition, by combining several epochs of observation, we expect to constrain the position of the known clumps and improve our knowledge on the dynamics of the disk. Methods. We observed the β Pictoris system over two nights in December 2019 in the 10- 12.5 μm coronagraphic filter. To evaluate the planet b flux contribution, we extracted the photometry at the expected position of the planet and compared it to the flux published in the literature. In addition, we used previous data from T-ReCS and VISIR in the mid-IR, updating the star's distance, to study the evolution of the position of the southwest clump that was initially observed in the planetary disk back in 2003. Results. While we did not detect the planet b, we were able to put constraints on the presence of circumplanetary material, ruling out the equivalent of a Saturn-like planetary ring around the planet. The disk presents several noticeable structures, including the known southwest clump. Using a 16-yr baseline, sampled with five epochs of observations, we were able to examine the evolution of the clump. We found that the clump orbits in a Keplerian motion with a semi-major axis of 56.1-0.3+0.4 au. In addition to the known clump, the images clearly show the presence of a second clump on the northeast side of the disk as well as possibly fainter and closer structures that are yet to be confirmed. Furthermore, we found correlations between the CO clumps detected with ALMA and the northeastern and southwestern clumps in the mid-IR images. Conclusions. If the circumplanetary material were located at the Roche radius, the maximum amount of dust determined from the flux upper limit around β Pictoris b would correspond to the mass of an asteroid of 5 km in diameter. Finally, the Keplerian motion of the southwestern clump is possibly indicative of a yet-to-be detected planet or signals the presence of a vortex.
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3.
  • Wang, Jason J., et al. (författare)
  • Keck/NIRC2 L'-Band Imaging of Jovian-Mass Accreting Protoplanets around PDS 70
  • 2020
  • Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 159:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We present L'-band imaging of the PDS 70 planetary system with Keck/NIRC2 using the new infrared pyramid wave front sensor. We detected both PDS 70 b and c in our images, as well as the front rim of the circumstellar disk. After subtracting off a model of the disk, we measured the astrometry and photometry of both planets. Placing priors based on the dynamics of the system, we estimated PDS 70 b to have a semimajor axis of au and PDS 70 c to have a semimajor axis of au (95% credible interval). We fit the spectral energy distribution (SED) of both planets. For PDS 70 b, we were able to place better constraints on the red half of its SED than previous studies and inferred the radius of the photosphere to be 2–3 R Jup. The SED of PDS 70 c is less well constrained, with a range of total luminosities spanning an order of magnitude. With our inferred radii and luminosities, we used evolutionary models of accreting protoplanets to derive a mass of PDS 70 b between 2 and 4 M Jup and a mean mass accretion rate between 3 × 10−7 and 8 × 10−7 M Jup/yr. For PDS 70 c, we computed a mass between 1 and 3 M Jup and mean mass accretion rate between 1 × 10−7 and 5 × 10−7 M Jup/yr. The mass accretion rates imply dust accretion timescales short enough to hide strong molecular absorption features in both planets' SEDs.
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4.
  • Akiyama, Eiji, et al. (författare)
  • SPIRAL STRUCTURE AND DIFFERENTIAL DUST SIZE DISTRIBUTION IN THE LkH alpha 330 DISK
  • 2016
  • Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 152:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 mu m) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkH alpha 330. As a. result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure. and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (beta) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side (beta = 2.0 +/- 0.5) but are much smaller in the west side beta = 0.7(-0.4)(+0.5), indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y-K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.
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5.
  • Chilcote, Jeffrey, et al. (författare)
  • SCExAO/CHARIS Direct Imaging of A Low-mass Companion At A Saturn-like Separation from an Accelerating Young A7 Star
  • 2021
  • Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 162:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the SCExAO direct imaging discovery and characterization of a low-mass companion to the nearby young A7IV star, HD 91312. SCExAO/CHARIS JHK (1.1–2.4 μm) spectra and SCExAO/HiCIAO H-band imaging identify the companion over a two year baseline in a highly inclined orbit with a maximum projected separation of 8 au. The companion, HD 91312 B, induces an 8.8σ astrometric acceleration on the star as seen with the Gaia & Hipparcos satellites and a long-term radial-velocity trend as previously identified by Borgniet et al. HD 91312 B's spectrum is consistent with that of an early-to-mid M dwarf. Hipparcos and Gaia absolute astrometry, radial-velocity data, and SCExAO/CHARIS astrometry constrain its dynamical mass to be 0.337-0.044+0.042 M⊙, consistent with - but far more precise than - masses derived from spectroscopy, and favors a nearly edge-on orbit with a semimajor axis of ∼9.7 au. This work is an example of precisely characterizing properties of low-mass companions at solar system-like scales from a combination of direct imaging, astrometry, and radial-velocity methods.
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6.
  • Currie, Thayne, et al. (författare)
  • Direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star
  • 2023
  • Ingår i: Science. - 0036-8075 .- 1095-9203. ; 380:6641, s. 198-203
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct imaging of gas giant exoplanets provides information on their atmospheres and the architectures of planetary systems. However, few planets have been detected in blind surveys with direct imaging. Using astrometry from the Gaia and Hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770. We confirmed the detection of this planet with direct imaging using the Subaru Coronagraphic Extreme Adaptive Optics instrument. The planet, HIP 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching Jupiter. Its dynamical mass is 13.9 to 16.1 Jupiter masses. The planet-to-star mass ratio [(7 to 8) × 10−3] is similar to that of other directly imaged planets. The planet’s atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around HR 8799.
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7.
  • Currie, Thayne, et al. (författare)
  • No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15 : LkCa 15 bcd are Likely Inner Disk Signals
  • 2019
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 877:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Two studies utilizing sparse aperture-masking (SAM) interferometry and H-alpha differential imaging have reported multiple Jovian companions around the young solar-mass star, LkCa 15 (LkCa 15 bcd): the first claimed direct detection of infant, newly formed planets (protoplanets). We present new near-infrared direct imaging/spectroscopy from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) integral field spectrograph and multi-epoch thermal infrared imaging from Keck/NIRC2 of LkCa 15 at high Strehl ratios. These data provide the first direct imaging look at the same wavelengths and in the same locations where previous studies identified the LkCa 15 protoplanets, and thus offer the first decisive test of their existence. The data do not reveal these planets. Instead, we resolve extended emission tracing a dust disk with a brightness and location comparable to that claimed for LkCa 15 bcd. Forward-models attributing this signal to orbiting planets are inconsistent with the combined SCExAO/CHARIS and Keck/NIRC2 data. An inner disk provides a more compelling explanation for the SAM detections and perhaps also the claimed H-alpha detection of LkCa 15 b. We conclude that there is currently no clear, direct evidence for multiple protoplanets orbiting LkCa 15, although the system likely contains at least one unseen Jovian companion. To identify Jovian companions around LkCa 15 from future observations, the inner disk should be detected and its effect modeled, removed, and shown to be distinguishable from planets. Protoplanet candidates identified from similar systems should likewise be clearly distinguished from disk emission through modeling.
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8.
  • Currie, Thayne, et al. (författare)
  • SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
  • 2020
  • Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 904:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of similar to 20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5 sigma astrometric acceleration on the star as detected with the Gaia and Hipparcos satellites. SCExAO/CHARIS JHK (1.1-2.4 mu m) spectra and Keck/NIRC2 L-p (3.78 mu m) photometry are best matched by a field L/T transition object: an older, higher-gravity, and less dusty counterpart to HR 8799 cde. Combining our astrometry with Gaia/Hipparcos data and archival Lick Observatory radial velocities, we measure a dynamical mass of 46.4 8 M-J and an eccentricity of e < 0.46 at 95% confidence. HD 33632 Ab's mass and mass ratio (4.0% 0.7%) are comparable to the low-mass brown dwarf GJ 758 B and intermediate between the more massive brown dwarf HD 19467 B and the (near-)planet-mass companions to HR 2562 and GJ 504. Using Gaia to select for direct imaging observations with the newest extreme adaptive optics systems can reveal substellar or even planet-mass companions on solar system-like scales at an increased frequency compared to blind surveys.
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9.
  • Currie, Thayne, et al. (författare)
  • SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of kappa And b : A Likely Young, Low-gravity Superjovian Companion
  • 2018
  • Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 156:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of kappa And b, a directly imaged low-mass companion orbiting a nearby B9V star. We detect kappa And b at a high signal-to-noise ratio and extract high-precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. kappa And b's spectrum best resembles that of a low-gravity LO-L1 dwarf (L0-L1 gamma). Its spectrum and luminosity are very well matched by 2MASS J0141-4633 and several other 12.5-15 M-J free-floating members of the 40 Myr old Tuc-Hor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13(-2)(+12) M-J), and a companion-to-primary mass ratio characteristic of other directly imaged planets (q similar to 0.0051(-0.001)(+0.005)). We did not unambiguously identify additional, more closely orbiting companions brighter and more massive than kappa And b down to p similar to 0.'' 3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points toward a likely eccentric orbit: a subset of acceptable orbits include those that are aligned with the star's rotation axis. However, kappa And b's semimajor axis is plausibly larger than 55 au and in a region where disk instability could form massive companions. Deeper high-contrast imaging of kappa And and low-resolution spectroscopy from extreme adaptive optics systems such as SCExAO/CHARIS and higher-resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help to clarify kappa And b's chemistry and whether its spectrum provides an insight into its formation environment.
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10.
  • Currie, Thayne, et al. (författare)
  • Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 36546
  • 2017
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 836:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r similar to 0.3 to r similar to 1 (34-114 au). The disk is oriented in a near east-west direction (PA similar to 75 degrees), is inclined by i similar to 70 degrees-75 degrees, and is strongly forward-scattering (g > 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t similar to 1-250 Myr), its kinematics and analysis of coeval stars suggest a young age (3-10 Myr) and a possible connection to Taurus-Auriga's star formation history. SCExAO's planet-to-star contrast ratios are comparable to the first-light Gemini Planet Imager contrasts; for an age of 10 Myr, we rule out planets with masses comparable to HR 8799 b beyond a projected separation of 23 au. A massive icy planetesimal disk or an unseen super-Jovian planet at r > 20 au may explain the disk's visibility. The HD 36546 debris disk may be the youngest debris disk yet imaged, is the first newly identified object from the now-operational SCExAO extreme AO system, is ideally suited for spectroscopic follow-up with SCExAO/CHARIS in 2017, and may be a key probe of icy planet formation and planet-disk interactions.
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