scholarly journals High-contrast Imaging with Fizeau Interferometry: the Case of Altair*

2022 ◽  
Vol 163 (2) ◽  
pp. 62
Author(s):  
E. Spalding ◽  
K. M. Morzinski ◽  
P. Hinz ◽  
J. Males ◽  
M. Meyer ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Active Phase ◽  
Phase Detector ◽  
Integration Time ◽  
Data Sets ◽  
Contrast Imaging ◽  
Science Data ◽  
Data Set ◽  
Nearby Star ◽  
High Contrast Imaging

Abstract The Large Binocular Telescope (LBT) has two 8.4 m primary mirrors that produce beams that can be combined coherently in a “Fizeau” interferometric mode. In principle, the Fizeau point-spread function (PSF) enables the probing of structure at a resolution up to three times better than that of the adaptive-optics-corrected PSF of a single 8.4 m telescope. In this work, we examined the nearby star Altair (5.13 pc, type A7V, hundreds of Myr to ≈1.4 Gyr) in the Fizeau mode with the LBT at Brα (4.05 μm) and carried out angular differential imaging to search for companions. This work presents the first filled-aperture LBT Fizeau science data set to benefit from a correcting mirror that provides active phase control. In the analysis of the λ/D angular regime, the sensitivity of the data set is down to ≈0.5 M ⊙ at 1″ for a 1.0 Gyr system. This sensitivity remains limited by the small amount of integration time, which is in turn limited by the instability of the Fizeau PSF. However, in the Fizeau fringe regime we attain sensitivities of Δm ≈ 5 at 0.″2 and put constraints on companions of 1.3 M ⊙ down to an inner angle of ≈0.″15, closer than any previously published direct imaging of Altair. This analysis is a pathfinder for future data sets of this type, and represents some of the first steps to unlocking the potential of the first Extremely Large Telescope. Fizeau observations will be able to reach dimmer targets with upgrades to the instrument, in particular the phase detector.

scholarly journals Medium-resolution integral-field spectroscopy for high-contrast exoplanet imaging

2018 ◽  
Vol 617 ◽  
pp. A144 ◽  
Author(s):  
H. J. Hoeijmakers ◽  
H. Schwarz ◽  
I. A. G. Snellen ◽  
R. J. de Kok ◽  
M. Bonnefoy ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Cross Correlation ◽  
High Contrast ◽  
Contrast Imaging ◽  
Data Set ◽  
Stellar Spectrum ◽  
High Contrast Imaging ◽  
Medium Resolution ◽  
Differential Imaging ◽  
Integral Field

Context. Angular differential imaging (ADI) and spectral differential imaging (SDI) are well-established high-contrast imaging techniques, but their application is challenging for companions at small angular separations from their host stars. Aims. The aim of this paper is to investigate to what extent adaptive-optics assisted, medium-resolution (R ~ 5000) integral field spectrographs (IFS) can be used to directly detect the absorption of molecular species in the spectra of planets and substellar companions when these are not present in the spectrum of the star. Methods. We analysed archival data of the β Pictoris system taken with the SINFONI integral field spectrograph located at ESO’s Very Large Telescope, originally taken to image β Pictoris b using ADI techniques. At each spatial position in the field, a scaled instance of the stellar spectrum is subtracted from the data after which the residuals are cross-correlated with model spectra. The cross-correlation co-adds the individual absorption lines of the planet emission spectrum constructively, while this is not the case for (residual) telluric and stellar features. Results. Cross-correlation with CO and H2O models results in significant detections of β Pictoris b with signal-to-noise ratios (S/Ns) of 13.7 and 16.4 respectively. Correlation with a T = 1700 K BT-Settl model provides a detection with an S/N of 22.8. This in contrast to application of ADI, which barely reveals the planet. While the adaptive optics system only achieved modest Strehl ratios of 19–27% leading to a raw contrast of 1:240 at the planet position, cross-correlation achieves a 3σ contrast limit of 2.7 × 10−5 in this 2.5 hr data set, a factor ~40 below the raw noise level at an angular distance of 0.36′′ from the star. Conclusions. Adaptive-optics assisted, medium-resolution IFS, such as SINFONI on the VLT and OSIRIS on the Keck Telescope, can be used for high-contrast imaging utilizing cross-correlation techniques for planets that are close to their star and embedded in speckle noise. We refer to this method as molecule mapping, and advocate its application to observations with future medium resolution instruments, in particular ERIS on the VLT, HARMONI on the ELT and NIRSpec, and MIRI on the JWST.

scholarly journals Robustness of prediction for extreme adaptive optics systems under various observing conditions

2020 ◽  
Vol 636 ◽  
pp. A81
Author(s):  
M. A. M. van Kooten ◽  
N. Doelman ◽  
M. Kenworthy
Keyword(s):  
Adaptive Optics ◽  
Linear Prediction ◽  
Spatial Information ◽  
Minimum Mean Square Error ◽  
Data Sets ◽  
Contrast Imaging ◽  
Improvement Factor ◽  
High Contrast Imaging ◽  
Average Improvement ◽  
Phase Variance

Context. For high-contrast imaging systems, such as VLT/SPHERE, the performance of the system at small angular separations is contaminated by the wind-driven halo in the science image. This halo is a result of the servo-lag error in the adaptive optics (AO) system due to the finite time between measuring the wavefront phase and applying the phase correction. One approach to mitigating the servo-lag error is predictive control. Aims. We aim to estimate and understand the potential on-sky performance that linear data-driven prediction would provide for VLT/SPHERE under various turbulence conditions. Methods. We used a linear minimum mean square error predictor and applied it to 27 different AO telemetry data sets from VLT/SPHERE taken over many nights under various turbulence conditions. We evaluated the performance of the predictor using residual wavefront phase variance as a performance metric. Results. We show that prediction always results in a reduction in the temporal wavefront phase variance compared to the current VLT/SPHERE AO performance. We find an average improvement factor of 5.1 in phase variance for prediction compared to the VLT/SPHERE residuals. When comparing to an idealised VLT/SPHERE, we find an improvement factor of 2.0. Under our 27 different cases, we find the predictor results in a smaller spread of the residual temporal phase variance. Finally, we show there is no benefit to including spatial information in the predictor in contrast to what might have been expected from the frozen flow hypothesis. A purely temporal predictor is best suited for AO on VLT/SPHERE. Conclusions. Linear prediction leads to a significant reduction in phase variance for VLT/SPHERE under a variety of observing conditions and reduces the servo-lag error. Furthermore, prediction improves the reliability of the AO system performance, making it less sensitive to different conditions.

scholarly journals PynPoint: a modular pipeline architecture for processing and analysis of high-contrast imaging data

2019 ◽  
Vol 621 ◽  
pp. A59 ◽  
Author(s):  
T. Stolker ◽  
M. J. Bonse ◽  
S. P. Quanz ◽  
A. Amara ◽  
G. Cugno ◽  
...  
Keyword(s):  
Data Reduction ◽  
Direct Detection ◽  
Principal Component ◽  
Monte Carlo Analysis ◽  
Data Sets ◽  
High Contrast ◽  
Imaging Data ◽  
Pipeline Architecture ◽  
Contrast Imaging ◽  
High Contrast Imaging

Context. The direct detection and characterization of planetary and substellar companions at small angular separations is a rapidly advancing field. Dedicated high-contrast imaging instruments deliver unprecedented sensitivity, enabling detailed insights into the atmospheres of young low-mass companions. In addition, improvements in data reduction and point spread function (PSF)-subtraction algorithms are equally relevant for maximizing the scientific yield, both from new and archival data sets. Aims. We aim at developing a generic and modular data-reduction pipeline for processing and analysis of high-contrast imaging data obtained with pupil-stabilized observations. The package should be scalable and robust for future implementations and particularly suitable for the 3–5 μm wavelength range where typically thousands of frames have to be processed and an accurate subtraction of the thermal background emission is critical. Methods. PynPoint is written in Python 2.7 and applies various image-processing techniques, as well as statistical tools for analyzing the data, building on open-source Python packages. The current version of PynPoint has evolved from an earlier version that was developed as a PSF-subtraction tool based on principal component analysis (PCA). Results. The architecture of PynPoint has been redesigned with the core functionalities decoupled from the pipeline modules. Modules have been implemented for dedicated processing and analysis steps, including background subtraction, frame registration, PSF subtraction, photometric and astrometric measurements, and estimation of detection limits. The pipeline package enables end-to-end data reduction of pupil-stabilized data and supports classical dithering and coronagraphic data sets. As an example, we processed archival VLT/NACO L′ and M′ data of β Pic b and reassessed the brightness and position of the planet with a Markov chain Monte Carlo analysis; we also provide a derivation of the photometric error budget.

High Contrast Imaging for Python (HCIPy): an open-source adaptive optics and coronagraph simulator

2018 ◽  
Author(s):  
Emiel H. Por ◽  
Sebastiaan Y. Haffert ◽  
Vikram Mark Radhakrishnan ◽  
David S. Doelman ◽  
Maaike van Kooten ◽  
...  
Keyword(s):  
Open Source ◽  
Adaptive Optics ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

scholarly journals A multi-decade record of high-quality fCO<sub>2</sub> data in version 3 of the Surface Ocean CO<sub>2</sub> Atlas (SOCAT)

2016 ◽  
Author(s):  
Dorothee C. E. Bakker ◽  
Benjamin Pfeil ◽  
Camilla S. Landa ◽  
Nicolas Metzl ◽  
Kevin M. O'Brien ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Surface Water ◽  
Data Collection ◽  
Data Availability ◽  
Data Sets ◽  
Science Data ◽  
High Quality ◽  
Data Set ◽  
Surface Ocean ◽  
Biogeochemical Models

Abstract. The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.5 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.4 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "Living Data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).

SPHERE+, Imaging young planets down to the snow line

2021 ◽  
Author(s):  
Anthony Boccaletti ◽  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Imaging Spectroscopy ◽  
Giant Planet ◽  
High Spectral Resolution ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Orbital Periods ◽  
Complementary Techniques ◽  
Technical Solutions

&lt;p&gt;SPHERE, the high contrast imaging facility at the VLT has contributed significantly to the exploration of planetary systems, by revealing many details in proto-planetary and debris disks, by measuring the atmospheric properties of young giant planets and by deriving constraints on the giant planet population in long orbital periods. Such achievements allow us to provide a better understanding of planetary formation and evolution. The versatility of SPHERE also enables various secondary and sometimes unexpected science cases owing to a large spectral coverage from the visible to the near IR, and the availability of several observing modes as imaging, spectroscopy and polarimetry. Yet the access to the region where planets are expected to form, is not complete and still represents a challenge. To overcome this limitation larger contrasts at shorter separations are definitely required.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;The SPHERE+ concept precisely aims to provide the capabilities to primarily access the bulk of the young giant planet population down to the snowline&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160; &lt;/span&gt;in order to bridge the gap with complementary techniques. As a second objective, SPHERE+ should be able to observe an increased sample of targets, fainter and redder than those observed in the first survey. Finally, SPHERE+ will provide a higher level of characterization of planet&amp;#8217;s atmospheres. To achieve these goals, SPHERE should be upgraded with a faster Adaptive Optics system to reach&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160; &lt;/span&gt;high contrasts at closer angular separations, together with a more sensitive wavefront sensor in the infrared to observe redder targets. Medium and high spectral resolution in the near infrared will be brought by a dedicated IFU spectrograph or taking advantage of the HiRISE project to combined SPHERE and CRIRES+. We will present the science cases and the technical solutions that are foreseen to reach the appropriate performances, and provide potential ways for such an upgrade. &lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;

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