131 research outputs found
Active focal-plane coronagraphy with liquid-crystal spatial-light modulators: Broadband contrast performance in the visible
The technological progress in spatial-light modulators (SLM) technology has
made it possible to use those devices as programmable active focal-plane phase
coronagraphic masks, opening the door to novel versatile and adaptive
high-contrast imaging observation strategies. However, the scalar nature of the
SLM-induced phase response is a potential hurdle when applying the approach to
wideband light, as is typical in astronomical imaging. For the first time, we
present laboratory results with broadband light (up to ~12pc bandwidth) for two
commercially-available SLM devices used as active focal-plane phase masks in
the visible regime (640 nm). It is shown that under ideal or realistic
telescope aperture conditions, the contrast performance is negligibly affected
in this bandwidth regime, reaching sufficient level for ground-based
high-contrast imaging, which is typically dominated by atmospheric residuals.Comment: 15 pages, 5 figure
Gastroesophageal Reflux Disease: Medical or Surgical Treatment?
Background. Gastroesophageal reflux disease is a common condition with increasing prevalence worldwide. The disease encompasses a broad spectrum of clinical symptoms and disorders from simple heartburn without esophagitis to erosive esophagitis with severe complications, such as esophageal strictures and intestinal metaplasia. Diagnosis is based mainly on ambulatory esophageal pH testing and endoscopy. There has been a long-standing debate about the best treatment approach for this troublesome disease. Methods and Results. Medical treatment with PPIs has an excellent efficacy in reversing the symptoms of GERD, but they should be taken for life, and long-term side effects do exist. However, patients who desire a permanent cure and have severe complications or cannot tolerate long-term treatment with PPIs are candidates for surgical treatment. Laparoscopic antireflux surgery achieves a significant symptom control, increased patient satisfaction, and complete withdrawal of antireflux medications, in the majority of patients. Conclusion. Surgical treatment should be reserved mainly for young patients seeking permanent results. However, the choice of the treatment schedule should be individualized for every patient. It is up to the patient, the physician and the surgeon to decide the best treatment option for individual cases
CROCODILE \\ Incorporating medium-resolution spectroscopy of close-in directly imaged exoplanets into atmospheric retrievals via cross-correlation
The investigation of the atmospheres of closely separated, directly imaged
gas giant exoplanets is challenging due to the presence of stellar speckles
that pollute their spectrum. To remedy this, the analysis of medium- to
high-resolution spectroscopic data via cross-correlation with spectral
templates (cross-correlation spectroscopy) is emerging as a leading technique.
We aim to define a robust Bayesian framework combining, for the first time,
three widespread direct-imaging techniques, namely photometry, low-resolution
spectroscopy, and medium-resolution cross-correlation spectroscopy in order to
derive the atmospheric properties of close-in directly imaged exoplanets. Our
framework CROCODILE (cross-correlation retrievals of directly imaged
self-luminous exoplanets) naturally combines the three techniques by adopting
adequate likelihood functions. To validate our routine, we simulated
observations of gas giants similar to the well-studied ~Pictoris~b
planet and we explored the parameter space of their atmospheres to search for
potential biases. We obtain more accurate measurements of atmospheric
properties when combining photometry, low- and medium-resolution spectroscopy
into atmospheric retrievals than when using the techniques separately as is
usually done in the literature. We find that medium-resolution () K-band cross-correlation spectroscopy alone is not suitable to constrain
the atmospheric properties of our synthetic datasets; however, this problem
disappears when simultaneously fitting photometry and low-resolution () spectroscopy between the Y and M bands. Our framework allows the
atmospheric characterisation of directly imaged exoplanets using the
high-quality spectral data that will be provided by the new generation of
instruments such as VLT/ERIS, JWST/MIRI, and ELT/METIS
Nuclear high-ionisation outflow in the Compton-thick AGN NGC6552 as seen by the JWST mid-infrared instrument
During the commissioning of the James Webb Space Telescope (JWST), the
mid-infrared instrument (MIRI) observed NGC6552 with the MIRI Imager and the
medium-resolution spectrograph (MRS). NGC6552 is an active galactic nucleus
(AGN) at redshift 0.0266 classified as a Seyfert 2 nucleus in the optical, and
Compton-thick AGN in X-rays. This work exemplifies and demonstrates the MRS
capabilities to study the mid-infrared (mid-IR) spectra and characterize the
physical conditions and kinematics of the ionized and molecular gas in the
nuclear regions of nearby galaxies. We obtained the nuclear, circumnuclear, and
central mid-IR spectra of NGC6552. They provide the first clear observational
evidence for a nuclear outflow in NGC6552. The outflow contributes to 677%
of the total line flux independent of the ionization potential (27 to 187 eV)
and critical densities (10 to 410 cm), showing an
average blue-shifted peak velocity of -12745 kms and an outflow
maximal velocity of 69880 kms. Since the mid-IR photons penetrate
dusty regions as efficiently as X-ray keV photons, we interpret these results
as the evidence for a highly ionized, non-stratified, AGN-powered, and fast
outflowing gas in a low density environment (few 10 cm) located
very close (<0.2kpc) to the Compton-thick AGN. Nine pure rotational molecular
Hydrogen lines are detected and spectrally resolved, and exhibit symmetric
Gaussian profiles, consistent with the galactic rotation, and with no evidence
of outflowing H material. We detect a warm H mass of
in the central region (1.8 kpc in diameter) of
the galaxy, with almost 30% of that mass in the circum-nuclear region. Line
ratios confirm that NGC6552 has a Seyfert nucleus with a black hole mass
estimated in the range of 0.6 to 6 million solar masses.Comment: 13 pages, 5 figures, 5 tables, accepted in A&
Observations of the planetary nebula SMP LMC 058 with the JWST MIRI medium resolution spectrometer
During the commissioning of JWST, the medium-resolution spectrometer (MRS) on the mid-infrared instrument (MIRI) observed the planetary nebula SMP LMC 058 in the Large Magellanic Cloud. The MRS was designed to provide medium resolution (R = λ/Δλ) 3D spectroscopy in the whole MIRI range. SMP LMC 058 is the only source observed in JWST commissioning that is both spatially and spectrally unresolved by the MRS and is a good test of JWST's capabilities. The new MRS spectra reveal a wealth of emission lines not previously detected in this planetary nebula. From these lines, the spectral resolving power (λ/Δλ) of the MRS is confirmed to be in the range R = 4000-1500, depending on the MRS spectral sub-band. In addition, the spectra confirm that the carbon-rich dust emission is from complex hydrocarbons and SiC grains and that there is little to no time evolution of the SiC dust and emission line strengths over a 17-yr epoch. These commissioning data reveal the great potential of the MIRI MRS for the study of circumstellar and interstellar material.</p
JWST MIRI/MRS in-flight absolute flux calibration and tailored fringe correction for unresolved sources
Context. The Medium Resolution Spectrometer (MRS) is one of the four observing modes of JWST/MIRI. Using JWST in-flight data of unresolved (point) sources, we can derive the MRS absolute spectral response function (ASRF) starting from raw data. Spectral fringing, caused by coherent reflections inside the detector arrays, plays a critical role in the derivation and interpretation of the MRS ASRF. The fringe corrections implemented in the current pipeline are not optimal for non-extended sources, and a high density of molecular features particularly inhibits an accurate correction. Aims. In this paper, we present an alternative way to calibrate the MIRI/MRS data. Firstly, we derive a fringe correction that accounts for the dependence of the fringe properties on the MIRI/MRS pupil illumination and detector pixel sampling of the point spread function. Secondly, we derive the MRS ASRF using an absolute flux calibrator observed across the full 5- 28 \ub5m wavelength range of the MRS. Thirdly, we apply the new ASRF to the spectrum of a G dwarf and compare it with the output of the JWST/MIRI default data reduction pipeline. Finally, we examine the impact of the different fringe corrections on the detectability of molecular features in the G dwarf and K giant. Methods. The absolute flux calibrator HD 163466 (A-star) was used to derive tailored point source fringe flats at each of the default dither locations of the MRS. The fringe-corrected point source integrated spectrum of HD 163466 was used to derive the MRS ASRF using a theoretical model for the stellar continuum. A cross-correlation was run to quantify the uncertainty on the detection of CO, SiO, and OH in the K giant and CO in the G dwarf for different fringe corrections. Results. The point-source-tailored fringe correction and ASRF are found to perform at the same level as the current corrections, beating down the fringe contrast to the sub-percent level in the G dwarf in the longer wavelengths, whilst mitigating the alteration of real molecular features. The same tailored solutions can be applied to other MRS unresolved targets. Target acquisition is required to ensure the pointing is accurate enough to apply this method. A pointing repeatability issue in the MRS limits the effectiveness of the tailored fringe flats is at short wavelengths. Finally, resulting spectra require no scaling to make the sub-bands match, and a dichroic spectral leak at 12.2 \ub5m is removed
Wavelength calibration and resolving power of the JWST MIRI Medium Resolution Spectrometer
Instrumentatio
The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems
The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles
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