56 research outputs found
Cystic artery pseudo-aneurysm: a complication of xanthogranulomatous cholecystitis
A 54-year-old man presented for radiology with pain and a feeling of fullness in the upper abdomen and an epigastric mass. Ultrasound revealed a large cystic mass with internal echoes, lying posterior and inferior to left lobe of the liver. The gallbladder was thick-walled and contracted, and contained a calculus and echogenic sludge. A cystic structure that produced swirling flow signals on colour Doppler was demonstrated within the gallbladder. The CT scan showed a thickened gallbladder with adjacent inflammation and a 2-cm pseudo-aneurysm in its wall. High-density material was present in the gallbladder lumen, in the extra-hepatic bile ducts and around the gastrohepatic ligament. A thick haemorrhagic pus, from which Escherichia coli was cultured, was drained from the gastrohepatic collection. An elective coeliac angiogram demonstrated a solitary pseudo-aneurysm of the medial branch of the cystic artery. Selective catheterisation of this artery with a micro-catheter enabled complete exclusion of the pseudo-aneurysm by a single micro-coil. Histological examination of the gallbladder, which was ultimately removed at open cholecystectomy, demonstrated xanthogranulomatous cholecystitis
Starspot occultations in infrared transit spectroscopy: the case of WASP-52b
Stellar activity is one of the main obstacles to high-precision exoplanet
observations and has motivated extensive studies in detection and
characterization problems. Most efforts focused on unocculted starspots in
optical transit spectrophotometry, while the impact of starspot crossings is
assumed to be negligible in the near-infrared. Here, we present
\textit{HST}/WFC3 transit observations of the active star WASP-52, hosting an
inflated hot Jupiter, which present a possible starspot occultation signal. By
using this data set as a benchmark, we investigated whether the masking of the
transit profile distortion or modeling it with both a starspot model and a
Gaussian process affects the shape of the transmission spectrum. Different
methods produced spectra with the same shape and a robust detection of water
vapor, and with different reference radii for the planet.
The solutions of all methods are in agreement and reached a similar level of
precision. Our WFC3 light curve of WASP-52b hints that starspot crossings might
become more problematic with \textit{JWST}'s higher sensitivity and complete
coverage of the transit profile.Comment: 15 pages, 15 figures, 5 tables, data available onlin
The HST PanCET Program:Hints of Na I and Evidence of a Cloudy Atmosphere for the Inflated Hot Jupiter WASP-52b
We present an optical to near-infrared transmission spectrum of the inflated
hot Jupiter WASP-52b using three transit observations from the Space Telescope
Imaging Spectrograph (STIS) mounted on the Hubble Space Telescope, combined
with Spitzer/Infrared Array Camera (IRAC) photometry at 3.6 microns and 4.5
microns. Since WASP-52 is a moderately active (log(Lx/Lbol) = -4.7) star, we
correct the transit light curves for the effect of stellar activity using
ground-based photometric monitoring data from the All-Sky Automated Survey for
Supernovae (ASAS-SN) and Tennessee State University's Automatic Imaging
Telescope (AIT). We bin the data in 38 spectrophotometric light curves from
0.29 to 4.5 microns and measure the transit depths to a median precision of 90
ppm. We compare the transmission spectrum to a grid of forward atmospheric
models and find that our results are consistent with a cloudy spectrum and
evidence of sodium at 2.3-sigma confidence, but no observable evidence of
potassium absorption even in the narrowest spectroscopic channel. We find that
the optical transmission spectrum of WASP-52b is similar to that of the
well-studied inflated hot Jupiter HAT-P-1b, which has comparable surface
gravity, equilibrium temperature, mass, radius, and stellar irradiation levels.
At longer wavelengths, however, the best fitting models for WASP-52b and
HAT-P-1b predict quite dissimilar properties, which could be confirmed with
observations at wavelengths longer than ~1 micron. The identification of
planets with common atmospheric properties and similar system parameters will
be insightful for comparative atmospheric studies with the James Webb Space
Telescope.Comment: 35 pages, 16 figures, accepted for publication in A
The Need for Laboratory Measurements and Ab Initio Studies to Aid Understanding of Exoplanetary Atmospheres
We are now on a clear trajectory for improvements in exoplanet observations
that will revolutionize our ability to characterize their atmospheric
structure, composition, and circulation, from gas giants to rocky planets.
However, exoplanet atmospheric models capable of interpreting the upcoming
observations are often limited by insufficiencies in the laboratory and
theoretical data that serve as critical inputs to atmospheric physical and
chemical tools. Here we provide an up-to-date and condensed description of
areas where laboratory and/or ab initio investigations could fill critical gaps
in our ability to model exoplanet atmospheric opacities, clouds, and chemistry,
building off a larger 2016 white paper, and endorsed by the NAS Exoplanet
Science Strategy report. Now is the ideal time for progress in these areas, but
this progress requires better access to, understanding of, and training in the
production of spectroscopic data as well as a better insight into chemical
reaction kinetics both thermal and radiation-induced at a broad range of
temperatures. Given that most published efforts have emphasized relatively
Earth-like conditions, we can expect significant and enlightening discoveries
as emphasis moves to the exotic atmospheres of exoplanets.Comment: Submitted as an Astro2020 Science White Pape
Detection of carbon monoxide's 4.6 micron fundamental band structure in WASP-39b's atmosphere with JWST NIRSpec G395H
Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad, double-branched structure composed of many individual absorption lines from 4.3 to 5.1 μm, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument (R ~ 2700) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 ± 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b's atmosphere and further supports the conclusions of low C/O and supersolar metallicities presented in the JTEC ERS papers for WASP-39b
Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-Correlation Techniques to JWST NIRSpec G395H Data
Carbon monoxide was recently reported in the atmosphere of the hot Jupiter
WASP-39b using the NIRSpec PRISM transit observation of this planet, collected
as part of the JWST Transiting Exoplanet Community Early Release Science (JTEC
ERS) Program. This detection, however, could not be confidently confirmed in
the initial analysis of the higher resolution observations with NIRSpec G395H
disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b
using the NIRSpec G395H data and cross-correlation techniques. We do this by
searching for the CO signal in the unbinned transmission spectrum of the planet
between 4.6 and 5.0 m, where the contribution of CO is expected to be
higher than that of other anticipated molecules in the planet's atmosphere. Our
search results in a detection of CO with a cross-correlation function (CCF)
significance of when using a template with only lines. The CCF significance of the CO signal increases to when including in the template lines from additional CO isotopologues,
with the largest contribution being from . Our results
highlight how cross-correlation techniques can be a powerful tool for unveiling
the chemical composition of exoplanetary atmospheres from medium-resolution
transmission spectra, including the detection of isotopologues.Comment: Accepted for publication in The Astrophysical Journal Letter
Fused Dithienogermolodithiophene Low Band Gap Polymers for High-Performance Organic Solar Cells without Processing Additives
A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot
Jupiters'') have been the subject of extensive efforts to determine their
atmospheric properties using thermal emission measurements from the Hubble and
Spitzer Space Telescopes. However, previous studies have yielded inconsistent
results because the small sizes of the spectral features and the limited
information content of the data resulted in high sensitivity to the varying
assumptions made in the treatment of instrument systematics and the atmospheric
retrieval analysis. Here we present a dayside thermal emission spectrum of the
ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on JWST. The
data span 0.85 to 2.85 m in wavelength at an average resolving power of
400 and exhibit minimal systematics. The spectrum shows three water emission
features (at 6 confidence) and evidence for optical opacity,
possibly due to H, TiO, and VO (combined significance of 3.8).
Models that fit the data require a thermal inversion, molecular dissociation as
predicted by chemical equilibrium, a solar heavy element abundance
(''metallicity'', M/H = 1.03 solar), and a
carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside
brightness temperature map, which shows a peak in temperature near the
sub-stellar point that decreases steeply and symmetrically with longitude
toward the terminators.Comment: JWST ERS bright star observations. Uploaded to inform JWST Cycle 2
proposals. Manuscript under review. 50 pages, 14 figures, 2 table
Photochemically produced SO2 in the atmosphere of WASP-39b
Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability1. However, no unambiguous photochemical products have been detected in exoplanet atmospheres so far. Recent observations from the JWST Transiting Exoplanet Community Early Release Science Program2,3 found a spectral absorption feature at 4.05 μm arising from sulfur dioxide (SO2) in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass (0.28 MJ) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of around 1,100 K (ref. 4). The most plausible way of generating SO2 in such an atmosphere is through photochemical processes5,6. Here we show that the SO2 distribution computed by a suite of photochemical models robustly explains the 4.05-μm spectral feature identified by JWST transmission observations7 with NIRSpec PRISM (2.7σ)8 and G395H (4.5σ)9. SO2 is produced by successive oxidation of sulfur radicals freed when hydrogen sulfide (H2S) is destroyed. The sensitivity of the SO2 feature to the enrichment of the atmosphere by heavy elements (metallicity) suggests that it can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an inferred metallicity of about 10× solar. We further point out that SO2 also shows observable features at ultraviolet and thermal infrared wavelengths not available from the existing observations
Photochemically-produced SO in the atmosphere of WASP-39b
Photochemistry is a fundamental process of planetary atmospheres that
regulates the atmospheric composition and stability. However, no unambiguous
photochemical products have been detected in exoplanet atmospheres to date.
Recent observations from the JWST Transiting Exoplanet Early Release Science
Program found a spectral absorption feature at 4.05 m arising from SO
in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass
(0.28 M) gas giant exoplanet orbiting a Sun-like star with an equilibrium
temperature of 1100 K. The most plausible way of generating SO in
such an atmosphere is through photochemical processes. Here we show that the
SO distribution computed by a suite of photochemical models robustly
explains the 4.05 m spectral feature identified by JWST transmission
observations with NIRSpec PRISM (2.7) and G395H (4.5). SO
is produced by successive oxidation of sulphur radicals freed when hydrogen
sulphide (HS) is destroyed. The sensitivity of the SO feature to the
enrichment of the atmosphere by heavy elements (metallicity) suggests that it
can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an
inferred metallicity of 10 solar. We further point out that
SO also shows observable features at ultraviolet and thermal infrared
wavelengths not available from the existing observations.Comment: 39 pages, 14 figures, accepted to be published in Natur
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