scholarly journals Astrometric and photometric accuracies in high contrast imaging: The SPHERE speckle calibration tool (SpeCal)

2018 ◽  
Vol 615 ◽  
pp. A92 ◽  
Author(s):  
R. Galicher ◽  
A. Boccaletti ◽  
D. Mesa ◽  
P. Delorme ◽  
R. Gratton ◽  
...  
Keyword(s):  
Circumstellar Disks ◽  
Observation Time ◽  
High Contrast ◽  
Large Telescope ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Very Large Telescope ◽  
User Friendly ◽  
Calibration Tool

Context. The consortium of the Spectro-Polarimetric High-contrast Exoplanet REsearch installed at the Very Large Telescope (SPHERE/VLT) has been operating its guaranteed observation time (260 nights over five years) since February 2015. The main part of this time (200 nights) is dedicated to the detection and characterization of young and giant exoplanets on wide orbits. Aims. The large amount of data must be uniformly processed so that accurate and homogeneous measurements of photometry and astrometry can be obtained for any source in the field. Methods. To complement the European Southern Observatory pipeline, the SPHERE consortium developed a dedicated piece of software to process the data. First, the software corrects for instrumental artifacts. Then, it uses the speckle calibration tool (SpeCal) to minimize the stellar light halo that prevents us from detecting faint sources like exoplanets or circumstellar disks. SpeCal is meant to extract the astrometry and photometry of detected point-like sources (exoplanets, brown dwarfs, or background sources). SpeCal was intensively tested to ensure the consistency of all reduced images (cADI, Loci, TLoci, PCA, and others) for any SPHERE observing strategy (ADI, SDI, ASDI as well as the accuracy of the astrometry and photometry of detected point-like sources. Results. SpeCal is robust, user friendly, and efficient at detecting and characterizing point-like sources in high contrast images. It is used to process all SPHERE data systematically, and its outputs have been used for most of the SPHERE consortium papers to date. SpeCal is also a useful framework to compare different algorithms using various sets of data (different observing modes and conditions). Finally, our tests show that the extracted astrometry and photometry are accurate and not biased.

scholarly journals Constraining the properties of HD 206893 B

2019 ◽  
Vol 627 ◽  
pp. L9 ◽  
Author(s):  
A. Grandjean ◽  
A.-M. Lagrange ◽  
H. Beust ◽  
L. Rodet ◽  
J. Milli ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Semimajor Axis ◽  
High Contrast ◽  
Brown Dwarf ◽  
Contrast Imaging ◽  
Dynamical Mass ◽  
Orbital Parameters ◽  
High Contrast Imaging ◽  
Very Large Telescope ◽  
Astrometric Data

Context. High contrast imaging enables the determination of orbital parameters for substellar companions (planets, brown dwarfs) from the observed relative astrometry and the estimation of model and age-dependent masses from their observed magnitudes or spectra. Combining astrometric positions with radial velocity gives direct constraints on the orbit and on the dynamical masses of companions. A brown dwarf was discovered with the VLT/SPHERE instrument at the Very Large Telescope (VLT) in 2017, which orbits at ∼11 au around HD 206893. Its mass was estimated between 12 and 50 MJ from evolutionary models and its photometry. However, given the significant uncertainty on the age of the system and the peculiar spectrophotometric properties of the companion, this mass is not well constrained. Aims. We aim at constraining the orbit and dynamical mass of HD 206893 B. Methods. We combined radial velocity data obtained with HARPS spectra and astrometric data obtained with the high contrast imaging VLT/SPHERE and VLT/NaCo instruments, with a time baseline less than three years. We then combined those data with astrometry data obtained by HIPPARCOS and Gaia with a time baseline of 24 yr. We used a Markov chain Monte Carlo approach to estimate the orbital parameters and dynamical mass of the brown dwarf from those data. Results. We infer a period between 21 and 33 yr and an inclination in the range 20−41° from pole-on from HD 206893 B relative astrometry. The RV data show a significant RV drift over 1.6 yr. We show that HD 206893 B cannot be the source of this observed RV drift as it would lead to a dynamical mass inconsistent with its photometry and spectra and with HIPPARCOS and Gaia data. An additional inner (semimajor axis in the range 1.4–2.6 au) and massive (∼15 MJ) companion is needed to explain the RV drift, which is compatible with the available astrometric data of the star, as well as with the VLT/SPHERE and VLT/NaCo nondetection.

The Dome C: A unique site for high-contrast imaging and extrasolar planet searching with a large telescope

2005 ◽  
Vol 14 ◽  
pp. 291-296 ◽  
Author(s):  
O. Lardière ◽  
M. Carbillet ◽  
A. Riccardi ◽  
P. Salinari ◽  
C. Aime
Keyword(s):  
Extrasolar Planet ◽  
High Contrast ◽  
Large Telescope ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Unique Site

scholarly journals Characterization of a photon counting EMCCD for space-based high contrast imaging spectroscopy of extrasolar planets

2014 ◽  
Author(s):  
Ashlee N. Wilkins ◽  
Michael W. McElwain ◽  
Timothy J. Norton ◽  
Bernie J. Rauscher ◽  
Johannes F. Rothe ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Imaging Spectroscopy ◽  
Photon Counting ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging

scholarly journals Adaptive Optics Imaging of Circumstellar Environments

2004 ◽  
Vol 221 ◽  
pp. 307-312
Author(s):  
Dániel Apai ◽  
Ilaria Pascucci ◽  
Hongchi Wang ◽  
Wolfgang Brandner ◽  
Thomas Henning ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Circumstellar Disks ◽  
Circumstellar Envelope ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Circumstellar Environments

We present results from our high-resolution, high-contrast imaging campaign targeting the circumstellar environments of young, nearby stars of different masses. The observations have been conducted using the ALFA/CA 3.5m and NACO UT4/VLT adaptive optics systems. In order to enhance the contrast we applied the methods PSF-subtraction and polarimetric differential imaging (PDI). The observations of young stars yielded the identification of numerous new companion candidates, the most interesting one being ∼ 0.5″ from FU Ori. We also obtained high-resolution near-infrared imaging of the circumstellar envelope of SU Aur and AB Aur. Our PDI of the TW Hya circumstellar disk traced back the disk emission as close as 0.1″ ≃ 6 AU from the star, the closest yet. Our results demonstrate the potential of the adaptive optics systems in achieving high-resolution and high-contrast imaging and thus in the study of circumstellar disks, envelopes and companions.

The CM120 Biotwin: a high-contrast objective lens, optimum cryo-vacuum and improved EDX performance

1995 ◽  
Vol 53 ◽  
pp. 584-585
Author(s):  
Uwe Lücken ◽  
Michael Felsmann ◽  
Wim M. Busing ◽  
Frank de Jong
Keyword(s):  
Life Science ◽  
Focal Length ◽  
Objective Lens ◽  
High Contrast ◽  
Contrast Imaging ◽  
X Ray ◽  
Forming Mechanism ◽  
Similar Image ◽  
High Contrast Imaging ◽  
Low Concentrations

A new microscope for the study of life science specimen has been developed. Special attention has been given to the problems of unstained samples, cryo-specimens and x-ray analysis at low concentrations.A new objective lens with a Cs of 6.2 mm and a focal length of 5.9 mm for high-contrast imaging has been developed. The contrast of a TWIN lens (f = 2.8 mm, Cs = 2 mm) and the BioTWTN are compared at the level of mean and SD of slow scan CCD images. Figure 1a shows 500 +/- 150 and Fig. 1b only 500 +/- 40 counts/pixel. The contrast-forming mechanism for amplitude contrast is dependent on the wavelength, the objective aperture and the focal length. For similar image conditions (same voltage, same objective aperture) the BioTWIN shows more than double the contrast of the TWIN lens. For phasecontrast specimens (like thin frozen-hydrated films) the contrast at Scherzer focus is approximately proportional to the √ Cs.

scholarly journals Anti-quenching NIR-II molecular fluorophores for in vivo high-contrast imaging and pH sensing

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Shangfeng Wang ◽  
Yong Fan ◽  
Dandan Li ◽  
Caixia Sun ◽  
Zuhai Lei ◽  
...  
Keyword(s):  
Ph Sensing ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging
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