Gas-giant planets emit a large fraction of their light in themid-infrared (gap3 mu m),where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. ...Of particular importance are the L- and M-band atmospheric windows (3-5 mu m), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT adaptive optics (AO) images of the HR 8799 planetary system in six narrow-band filters from 3 to 4 mu m, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3 mu m band. These systems encompass the five known exoplanets with luminosities consistent with L arrow right T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature (spanned by the narrow-band filters and encompassed by the broader 3.3 mu m filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the object's appearance. For the HR 8799 planets, we present new models that suggest the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.
We present optical and near-infrared high-contrast images of the transitional disk HD 100546 taken with the Magellan Adaptive Optics system (MagAO) and the Gemini Planet Imager (GPI). GPI data ...include both polarized intensity and total intensity imagery, and MagAO data are taken in Simultaneous Differential Imaging mode at H . The new GPI H-band total intensity data represent a significant enhancement in sensitivity and field rotation compared to previous data sets and enable a detailed exploration of substructure in the disk. The data are processed with a variety of differential imaging techniques (polarized, angular, reference, and simultaneous differential imaging) in an attempt to identify the disk structures that are most consistent across wavelengths, processing techniques, and algorithmic parameters. The inner disk cavity at 15 au is clearly resolved in multiple data sets, as are a variety of spiral features. While the cavity and spiral structures are identified at levels significantly distinct from the neighboring regions of the disk under several algorithms and with a range of algorithmic parameters, emission at the location of HD 100546 "c" varies from point-like under aggressive algorithmic parameters to a smooth continuous structure with conservative parameters, and is consistent with disk emission. Features identified in the HD 100546 disk bear qualitative similarity to computational models of a moderately inclined two-armed spiral disk, where projection effects and wrapping of the spiral arms around the star result in a number of truncated spiral features in forward-modeled images.
ABSTRACT We report on the performance of a vector apodizing phase plate coronagraph that operates over a wavelength range of 2-5 m and is installed in MagAO/Clio2 at the 6.5 m Magellan Clay telescope ...at Las Campanas Observatory, Chile. The coronagraph manipulates the phase in the pupil to produce three beams yielding two coronagraphic point-spread functions (PSFs) and one faint leakage PSF. The phase pattern is imposed through the inherently achromatic geometric phase, enabled by liquid crystal technology and polarization techniques. The coronagraphic optic is manufactured using a direct-write technique for precise control of the liquid crystal pattern and multitwist retarders for achromatization. By integrating a linear phase ramp to the coronagraphic phase pattern, two separated coronagraphic PSFs are created with a single pupil-plane optic, which makes it robust and easy to install in existing telescopes. The two coronagraphic PSFs contain a 180° dark hole on each side of a star, and these complementary copies of the star are used to correct the seeing halo close to the star. To characterize the coronagraph, we collected a data set of a bright (mL = 0-1) nearby star with ∼1.5 hr of observing time. By rotating and optimally scaling one PSF and subtracting it from the other PSF, we see a contrast improvement by 1.46 magnitudes at 3.5 λ / D . With regular angular differential imaging at 3.9 m, the MagAO vector apodizing phase plate coronagraph delivers a 5 Δ mag contrast of 8.3 ( = 10 − 3.3 ) at 2 λ / D and 12.2 ( = 10 − 4.8 ) at 3.5 λ / D .
In this paper we describe the procedure for the optical calibration of large size deformable mirrors, acting as wavefront correctors for adaptive optics systems. Adaptive optics compensate the ...disturbance due to the atmospheric turbulence to restore the telescope resolution. We will showcase in particular the activities performed for the Adaptive Secondary Mirror (ASM) of the Magellan Adaptive Optics system (MagAO), which is an instrument for the 6.5 m Magellan Clay Telescope, located at Las Campanas Observatory, in Chile. The MagAO ASM calibration is part of the MagAO-2K project, a major MagAO upgrade that started in 2016 with the goal of boosting adaptive optics (AO) correction at visible wavelengths to image exoplanets. For the first time, the optical quality of MagAO mirror is reported. We describe the procedures developed to achieve high SNR interferometric measurements of the ASM modes under the presence of dome convection noise and telescope vibrations. These measurements were required to produce an improved control matrix with up to 500 modes to close the AO loop on sky with enhanced performances. An updated slaving algorithm was developed to improve the control of actuators vignetted by the central obscuration. The calibrations yielded also a new ASM flattening command, updating the one in use since the MagAO commissioning in 2013. With the new flattening command, a 22 nm RMS surface error was achieved. Finally, we present on-sky results showing the MagAO performance achieved with the new calibrations.
ABSTRACT
The vector Apodizing Phase Plate (vAPP) is a class of pupil plane coronagraph that enables high-contrast imaging by modifying the Point Spread Function (PSF) to create a dark hole of deep ...flux suppression adjacent to the PSF core. Here, we recover the known brown dwarf HR 2562 B using a vAPP coronagraph, in conjunction with the Magellan Adaptive Optics (MagAO) system, at a signal-to-noise of S/N = 3.04 in the lesser studied L-band regime. The data contained a mix of field and pupil-stabilized observations, hence we explored three different processing techniques to extract the companion, including Flipped Differential Imaging (FDI), a newly devised Principal Component Analysis (PCA)-based method for vAPP data. Despite the partial field-stabilization, the companion is recovered sufficiently to measure a 3.94 $\mu\mathrm{ m}$ narrow-band contrast of (3.05 ± 1.00) × 10−4 ($\Delta \, {\rm m}_{3.94 \mu {\rm m}}$ = 8.79 ± 0.36 mag). Combined with archival GPI and SPHERE observations, our atmospheric modelling indicates a spectral type at the L/T transition with mass M = 29 ± 15 MJup, consistent with literature results. However, effective temperature and surface gravity vary significantly depending on the wavebands considered (1200 ≤ Teff(K) ≤ 1700 and 4.0 ≤ log(g)(dex) ≤ 5.0), reflecting the challenges of modelling objects at the L/T transition. Observations between 2.4 and 3.2 $\mu\mathrm{ m}$ will be more effective in distinguishing cooler brown dwarfs due to the onset of absorption bands in this region. We explain that instrumental scattered light and wind-driven halo can be detrimental to FDI+PCA and thus must be sufficiently mitigated to use this processing technique. We thus demonstrate the potential of vAPP coronagraphs in the characterization of high-contrast substellar companions, even in sub-optimal conditions, and provide new complementary photometry of HR 2562 B.
ABSTRACT
Improving direct detection capability close to the star through improved star subtraction and post-processing techniques is vital for discovering new low-mass companions and characterizing ...known ones at longer wavelengths. We present results of 17 binary star systems observed with the Magellan adaptive optics system (MagAO) and the Clio infrared camera on the Magellan Clay Telescope using binary differential imaging (BDI). BDI is an application of reference differential imaging (RDI) and angular differential imaging (ADI) applied to wide binary star systems (2 arcsec <Δρ < 10 arcsec) within the isoplanatic patch in the infrared. Each star serves as the point spread function (PSF) reference for the other, and we performed PSF estimation and subtraction using principal component analysis. We report contrast and mass limits for the 35 stars in our initial survey using BDI with MagAO/Clio in L′ and 3.95 µm bands. Our achieved contrasts varied between systems, and spanned a range of contrasts from 3.0 to 7.5 magnitudes and a range of separations from 0.2 to 2 arcsec. Stars in our survey span a range of masses, and our achieved contrasts correspond to late-type M-dwarf masses down to ∼10 MJup. We also report detection of a candidate companion signal at 0.2 arcsec (18 au) around HIP 67506 A (SpT G5V, mass ∼1.2 M⊙), which we estimate to be $\sim 60-90 \, \rm{M_{Jup}}$. We found that the effectiveness of BDI is highest for approximately equal brightness binaries in high-Strehl conditions.
Abstract
We present limits on the lens flux of OGLE-2007-BLG-224 based on MagAO imaging taken seven years after the microlensing event. At the time of the observations, the lens should have been ...separated from the microlensing source by 292 mas. However, no new sources are detected with MagAO. We place an upper limit on the lens flux of
H
> 20.57. This measurement supports the conclusion of Gould et al. that the lens in this event should be a brown dwarf. This is the first test of a prediction based on the terrestrial microlens parallax effect and the first AO confirmation of a substellar/dark microlens.
We present the results of the largest L′ (3.8 m) 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 MJup planet from 5 to 50 au. This limit leaves open the possibility that planets in this range are common.
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