scholarly journals PCA-based approach for subtracting thermal background emission in high-contrast imaging data

2018 ◽  
Vol 611 ◽  
pp. A23 ◽  
Author(s):  
S. Hunziker ◽  
S. P. Quanz ◽  
A. Amara ◽  
M. R. Meyer
Keyword(s):  
Background Subtraction ◽  
Complete Data ◽  
Phase Mask ◽  
High Contrast ◽  
Imaging Data ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Background Emission ◽  
Data Reductions ◽  
Thermal Background

Aims.Ground-based observations at thermal infrared wavelengths suffer from large background radiation due to the sky, telescope and warm surfaces in the instrument. This significantly limits the sensitivity of ground-based observations at wavelengths longer than ~3 μm. The main purpose of this work is to analyse this background emission in infrared high-contrast imaging data as illustrative of the problem, show how it can be modelled and subtracted and demonstrate that it can improve the detection of faint sources, such as exoplanets. Methods. We used principal component analysis (PCA) to model and subtract the thermal background emission in three archival high-contrast angular differential imaging datasets in the M′ and L′ filter. We used an M′ dataset of β Pic to describe in detail how the algorithm works and explain how it can be applied. The results of the background subtraction are compared to the results from a conventional mean background subtraction scheme applied to the same dataset. Finally, both methods for background subtraction are compared by performing complete data reductions. We analysed the results from the M′ dataset of HD 100546 only qualitatively. For the M′ band dataset of β Pic and the L′ band dataset of HD 169142, which was obtained with an angular groove phase mask vortex vector coronagraph, we also calculated and analysed the achieved signal-to-noise ratio (S/N). Results. We show that applying PCA is an effective way to remove spatially and temporarily varying thermal background emission down to close to the background limit. The procedure also proves to be very successful at reconstructing the background that is hidden behind the point spread function. In the complete data reductions, we find at least qualitative improvements for HD 100546 and HD 169142, however, we fail to find a significant increase in S/N of β Pic b. We discuss these findings and argue that in particular datasets with strongly varying observing conditions or infrequently sampled sky background will benefit from the new approach.

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.

In-lab testing of six-level phase mask coronagraphs onto the high-contrast imaging THD2 bench

2018 ◽  
Author(s):  
Fabien Patru ◽  
Pierre Baudoz ◽  
Raphaël Galicher ◽  
Qing Cao ◽  
Kai Wang ◽  
...  
Keyword(s):  
Phase Mask ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

scholarly journals High-contrast Imaging with a Small, Well-corrected Subaperture and a Phase-mask Coronagraph

2009 ◽  
Author(s):  
D. Mawet ◽  
E. Serabyn ◽  
Tomonori Usuda ◽  
Motohide Tamura ◽  
Miki Ishii
Keyword(s):  
Phase Mask ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

Multiplicity study of T Tauri starsin the Lupus star forming region

2018 ◽  
Vol 14 (S345) ◽  
pp. 318-319
Author(s):  
M. Mugrauer ◽  
C. Ginski ◽  
N. Vogt ◽  
R. Neuhäuser
Keyword(s):  
Main Sequence ◽  
Average Distance ◽  
High Contrast ◽  
Imaging Data ◽  
Main Sequence Stars ◽  
Contrast Imaging ◽  
Star Forming ◽  
High Contrast Imaging ◽  
T Tauri ◽  
Triple Star

AbstractWe carried out a high contrast imaging search for (sub)stellar companions of young pre-main sequence stars in the Lupus star forming region. For this project we utilized NACO/ESO-VLT, operated at the Paranal observatory. On this poster, we presented the results of this survey. In several observing campaigns we could obtain diffraction limited deep IR imaging data and detected faint co-moving companions around our targets, whose astro- and photometry was determined in all observing epochs. The co-moving companions found in our survey exhibit angular separations in the range between about 0.1 and a few arcsecs, i.e. projected separations between about 10 and a few hundreds of au, at the average distance of our targets of about 140 pc. Beside several new binary and triple star systems, whose multiplicity was revealed in this survey, also faint co-moving companions in the substellar mass regime could be identified close to some of our targets.

scholarly journals Laboratory validation of the dual-zone phase mask coronagraph in broadband light at the high-contrast imaging THD testbed

2016 ◽  
Vol 592 ◽  
pp. A119 ◽  
Author(s):  
J. R. Delorme ◽  
M. N’Diaye ◽  
R. Galicher ◽  
K. Dohlen ◽  
P. Baudoz ◽  
...  
Keyword(s):  
Phase Mask ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

scholarly journals Unveiling the β Pictoris system, coupling high contrast imaging, interferometric, and radial velocity data

2020 ◽  
Vol 642 ◽  
pp. A18
Author(s):  
A. M. Lagrange ◽  
P. Rubini ◽  
M. Nowak ◽  
S. Lacour ◽  
A. Grandjean ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Gravity Data ◽  
Giant Planet ◽  
Base Line ◽  
High Contrast ◽  
Imaging Data ◽  
Contrast Imaging ◽  
Orbital Parameters ◽  
High Contrast Imaging ◽  
The Impact

Context. The nearby and young β Pictoris system hosts a well resolved disk, a directly imaged massive giant planet orbiting at ≃9 au, as well as an inner planet orbiting at ≃2.7 au, which was recently detected through radial velocity (RV). As such, it offers several unique opportunities for detailed studies of planetary system formation and early evolution. Aims. We aim to further constrain the orbital and physical properties of β Pictoris b and c using a combination of high contrast imaging, long base-line interferometry, and RV data. We also predict the closest approaches or the transit times of both planets, and we constrain the presence of additional planets in the system. Methods. We obtained six additional epochs of SPHERE data, six additional epochs of GRAVITY data, and five additional epochs of RV data. We combined these various types of data in a single Markov-chain Monte Carlo analysis to constrain the orbital parameters and masses of the two planets simultaneously. The analysis takes into account the gravitational influence of both planets on the star and hence their relative astrometry. Secondly, we used the RV and high contrast imaging data to derive the probabilities of presence of additional planets throughout the disk, and we tested the impact of absolute astrometry. Results. The orbital properties of both planets are constrained with a semi-major axis of 9.8 ± 0.4 au and 2.7 ± 0.02 au for b and c, respectively, and eccentricities of 0.09 ± 0.1 and 0.27 ± 0.07, assuming the HIPPARCOS distance. We note that despite these low fitting error bars, the eccentricity of β Pictoris c might still be over-estimated. If no prior is provided on the mass of β Pictoris b, we obtain a very low value that is inconsistent with what is derived from brightness-mass models. When we set an evolutionary model motivated prior to the mass of β Pictoris b, we find a solution in the 10–11 MJup range. Conversely, β Pictoris c’s mass is well constrained, at 7.8 ± 0.4 MJup, assuming both planets are on coplanar orbits. These values depend on the assumptions on the distance of the β Pictoris system. The absolute astrometry HIPPARCOS-Gaia data are consistent with the solutions presented here at the 2σ level, but these solutions are fully driven by the relative astrometry plus RV data. Finally, we derive unprecedented limits on the presence of additional planets in the disk. We can now exclude the presence of planets that are more massive than about 2.5 MJup closer than 3 au, and more massive than 3.5 MJup between 3 and 7.5 au. Beyond 7.5 au, we exclude the presence of planets that are more massive than 1–2 MJup. Conclusions. Combining relative astrometry and RVs allows one to precisely constrain the orbital parameters of both planets and to give lower limits to potential additional planets throughout the disk. The mass of β Pictoris c is also well constrained, while additional RV data with appropriate observing strategies are required to properly constrain the mass of β Pictoris b.

scholarly journals Search for cool extrasolar giant planets combining coronagraphy, spectral and angular differential imaging

2013 ◽  
Vol 8 (S299) ◽  
pp. 21-25
Author(s):  
Anne-Lise Maire ◽  
Anthony Boccaletti ◽  
Julien Rameau ◽  
Gaël Chauvin ◽  
Anne-Marie Lagrange ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Point Sources ◽  
Giant Planets ◽  
Phase Mask ◽  
Evolutionary Models ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Nearby Stars ◽  
Differential Imaging

AbstractSpectral differential imaging (SDI) is part of the observing strategy of current and on-going high-contrast imaging instruments on ground-based telescopes. Although it improves the star light rejection, SDI attenuates the signature of off-axis companions to the star, just like angular differential imaging (ADI). However, the attenuation due to SDI has the peculiarity of being dependent on the spectral properties of the companions. To date, no study has investigated these effects. Our team is addressing this problem based on data from a direct imaging survey of 16 stars combining the phase-mask coronagraph, the SDI and the ADI modes of VLT/NaCo. The objective of the survey is to search for cool (Teff<1000-1300 K) giant planets at separations of 5-10 AU orbiting young, nearby stars (<200 Myr, <25 pc). The data analysis did not yield any detections. As for the estimation of the sensivity limits of SDI-processed images, we show that it requires a different analysis than that used in ADI-based surveys. Based on a method using the flux predictions of evolutionary models and avoiding the estimation of contrast, we determine directly the mass sensivity limits of the survey for the ADI processing alone and with the combination of SDI and ADI. We show that SDI does not systematically improve the sensitivity due to the spectral properties and self-subtraction of point sources.

Lab results of the circular phase mask concepts for high-contrast imaging of exoplanets

2012 ◽  
Author(s):  
Mamadou N'Diaye ◽  
Kjetil Dohlen ◽  
Thierry Fusco ◽  
Kacem El Hadi ◽  
Rémi Soummer ◽  
...  
Keyword(s):  
Phase Mask ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

scholarly journals Companion search around β Pictoris with the newly commissioned L'-band vector vortex coronagraph on VLT/NACO

2013 ◽  
Vol 8 (S299) ◽  
pp. 50-51
Author(s):  
D. Mawet ◽  
O. Absil ◽  
J. Milli ◽  
P. Baudoz ◽  
A. Boccaletti ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Diffraction Limit ◽  
Phase Mask ◽  
Circumstellar Disk ◽  
High Contrast ◽  
Contrast Imaging ◽  
Subwavelength Gratings ◽  
High Contrast Imaging ◽  
Wide Range ◽  
L Band

AbstractHere we present the installation and successful commissioning of an L'-band Annular Groove Phase Mask (AGPM) coronagraph on VLT/NACO. The AGPM is a vector vortex coronagraph made from diamond subwavelength gratings tuned to the L' band. The vector vortex coronagraph enables high contrast imaging at very small inner working angle (here 0″.09, the diffraction limit of the VLT at L'), potentially being the key to a new parameter space. During technical and science verification runs, we discovered a late-type companion at two beamwidths from an F0V star (Mawet et al. 2013), and imaged the inner regions of β Pictoris down to the previously unexplored projected radius of 1.75 AU. The circumstellar disk was also resolved from ≃ 1″ to 5″ (see J. Milli et al., these proceedings). These results showcase the potential of the NACO L-band AGPM over a wide range of spatial scales.

scholarly journals Spectral and atmospheric characterisation of a new benchmark brown dwarf HD 13724 B

2020 ◽  
Vol 635 ◽  
pp. A203 ◽  
Author(s):  
E. L. Rickman ◽  
D. Ségransan ◽  
J. Hagelberg ◽  
J.-L. Beuzit ◽  
A. Cheetham ◽  
...  
Keyword(s):  
Radial Velocity ◽  
High Contrast ◽  
Imaging Data ◽  
Brown Dwarf ◽  
Low Resolution ◽  
Contrast Imaging ◽  
Echelle Spectrograph ◽  
Dynamical Mass ◽  
High Contrast Imaging ◽  
Mass Estimate

Context. HD 13724 is a nearby solar-type star at 43.48 ± 0.06 pc hosting a long-period low-mass brown dwarf detected with the CORALIE echelle spectrograph as part of the historical CORALIE radial-velocity search for extra-solar planets. The companion has a minimum mass of 26.77−2.2+4.4 MJup and an expected semi-major axis of ~240 mas making it a suitable target for further characterisation with high-contrast imaging, in particular to measure its inclination, mass, and spectrum and thus establish its substellar nature. Aims. Using high-contrast imaging with the SPHERE instrument on the Very Large Telescope (VLT), we are able to directly image a brown dwarf companion to HD 13724 and obtain a low-resolution spectrum. Methods. We combine the radial-velocity measurements of CORALIE and HARPS taken over two decades and high-contrast imaging from SPHERE to obtain a dynamical mass estimate. From the SPHERE data we obtain a low-resolution spectrum of the companion from Y to J band, as well as photometric measurements from IRDIS in the J, H, and K bands. Results. Using high-contrast imaging with the SPHERE instrument at the VLT, we report the first images of a brown dwarf companion orbiting the host star HD 13724. It has an angular separation of 175.6 ± 4.5 mas and an H-band contrast of 10.61 ± 0.16 mag, and using the age estimate of the star to be ~1 Gyr gives an isochronal mass estimate of ~44 MJup. By combining radial-velocity and imaging data we also obtain a dynamical mass of 50.5−3.5+3.3 MJup. Through fitting an atmospheric model, we estimate a surface gravity of logg = 5.5 and an effective temperature of 1000 K. A comparison of its spectrum with observed T dwarfs estimates a spectral type of T4 or T4.5, with a T4 object providing the best fit.

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