52 research outputs found
An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet.
Broad absorption signatures from alkali metals, such as the sodium (Na I) and potassium (K I) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets1-3. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles4-6. Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances7-9. Here we report an optical transmission spectrum for the 'hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logΔNaâ=â[Formula: see text], and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Zp/ZÊâ=â[Formula: see text]). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets10-12
Solar-to-supersolar sodium and oxygen absolute abundances for a âhot Saturnâ orbiting a metal-rich star
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this recordDATA AVAILABILITY:
Raw and calibrated Hubble Space Telescope spectral transit time
series and Spitzer Space Telescope transit and eclipse time series photometry are publicly available at the Mikulski Archive
for Space Telescopes (MAST; https://archive.stsci.edu)
and the NASA/IPAC Infrared Science Archive (IRSA; https:
//sha.ipac.caltech.edu/applications/Spitzer/SHA/), respectively. TESS light curves are publicly available at the MAST
archive. Calibrated and extracted high-resolution FEROS spectra are
publicly available via the European Southern Observatoryâs Spectral Data Products Query Form (http://archive.eso.org/wdb/
wdb/adp/phase3_spectral/form). Broad-band light curves are
publicly available at the webpage of the All-Sky Automated Survey
for Supernovae (ASAS-SN; https://asas-sn.osu.edu).We present new analysis of infrared transmission spectroscopy of the cloud-free hot-Saturn WASP-96b performed with the Hubble and Spitzer Space Telescopes (HST and Spitzer). The WASP-96b spectrum exhibits the absorption feature from water in excellent agreement with synthetic spectra computed assuming a cloud-free atmosphere. The HST-Spitzer spectrum is coupled with Very Large Telescope (VLT) optical transmission spectroscopy which reveals the full pressure-broadened profile of the sodium absorption feature and enables the derivation of absolute abundances. We confirm and correct for a spectral offset of of the VLT data relative to the HST-Spitzer spectrum. This offset can be explained by the assumed radius for the common-mode correction of the VLT spectra, which is a well-known feature of ground-based transmission spectroscopy. We find evidence for a lack of chromospheric and photometric activity of the host star which, therefore, make a negligible contribution to the offset. We measure abundances for Na and O that are consistent with solar to supersolar, with abundances relative to solar values of and , respectively. We complement the transmission spectrum with new thermal emission constraints from Spitzer observations at 3.6 and 4.5Όm, which are best explained by the spectrum of an atmosphere with a temperature decreasing with altitude. A fit to the spectrum assuming an isothermal blackbody atmosphere constrains the dayside temperature to be Tp = 1545 ± 90K.Science and Technology Facilities CouncilUK Research and InnovationNASAEuropean Research CouncilLeverhulme TrustSTSc
Validity of a self-administered food frequency questionnaire (FFQ) and its generalizability to the estimation of dietary folate intake in Japan
BACKGROUND: In an epidemiological study, it is essential to test the validity of the food frequency questionnaire (FFQ) for its ability to estimate dietary intake. The objectives of our study were to 1) validate a FFQ for estimating folate intake, and to identify the foods that contribute to inter-individual variation of folate intake in the Japanese population. METHODS: Validity of the FFQ was evaluated using 28-day weighed dietary records (DRs) as gold standard in the two groups independently. In the group for which the FFQ was developed, validity was evaluated by Spearman's correlation coefficients (CCs), and linear regression analysis was used to identify foods with large inter-individual variation. The cumulative mean intake of these foods was compared with total intake estimated by the DR. The external validity of the FFQ and intake from foods on the same list were evaluated in the other group to verify generalizability. Subjects were a subsample from the Japan Public Health Center-based prospective Study who volunteered to participate in the FFQ validation study. RESULTS: CCs for the internal validity of the FFQ were 0.49 for men and 0.29 and women, while CCs for external validity were 0.33 for men and 0.42 for women. CCs for cumulative folate intake from 33 foods selected by regression analysis were also applicable to an external population. CONCLUSION: Our FFQ was valid for and generalizable to the estimation of folate intake. Foods identified as predictors of inter-individual variation in folate intake were also generalizable in Japanese populations. The FFQ with 138 foods was valid for the estimation of folate intake, while that with 33 foods might be useful for estimating inter-individual variation and ranking of individual folate intake
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The transiting exoplanet community early release science program for JWST
The transiting exoplanet community early release science program for JWST
The James Webb Space Telescope (JWST) presents the opportunity to transform
our understanding of planets and the origins of life by revealing the
atmospheric compositions, structures, and dynamics of transiting exoplanets in
unprecedented detail. However, the high-precision, time-series observations
required for such investigations have unique technical challenges, and prior
experience with other facilities indicates that there will be a steep learning
curve when JWST becomes operational. In this paper we describe the science
objectives and detailed plans of the Transiting Exoplanet Community Early
Release Science (ERS) Program, which is a recently approved program for JWST
observations early in Cycle 1. The goal of this project, for which the obtained
data will have no exclusive access period, is to accelerate the acquisition and
diffusion of technical expertise for transiting exoplanet observations with
JWST, while also providing a compelling set of representative datasets that
will enable immediate scientific breakthroughs. The Transiting Exoplanet
Community ERS Program will exercise the time-series modes of all four JWST
instruments that have been identified as the consensus highest priorities,
observe the full suite of transiting planet characterization geometries
(transits, eclipses, and phase curves), and target planets with host stars that
span an illustrative range of brightnesses. The observations in this program
were defined through an inclusive and transparent process that had
participation from JWST instrument experts and international leaders in
transiting exoplanet studies. Community engagement in the project will be
centered on a two-phase Data Challenge that culminates with the delivery of
planetary spectra, time-series instrument performance reports, and open-source
data analysis toolkits in time to inform the agenda for Cycle 2 of the JWST
mission
Early Release Science of the exoplanetWASP-39b with JWST NIRISS
This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this recordData Availability:
The raw data from this study are publicly available via the Space Science Telescope Institute's
Mikulski Archive for Space Telescopes (https://archive.stsci.edu/). The data which was used to
create all of the figures in this manuscript are freely available on Zenodo and GitHub (Zenodo
Link;https://github.com/afeinstein20/wasp39b_niriss_paper). All additional data is available upon
request.Code Availability:
The following are open-source pipelines written in Python that are available either through the
Python Package Index (PyPI) or GitHub that were used throughout this work:
Eureka! (https://github.com/kevin218/Eureka); nirHiss (https://github.com/afeinstein20/nirhiss);
supreme-SPOON (https://github.com/radicamc/supreme-spoon); transitspectroscopy
(https://github.com/nespinoza/transitspectroscopy/tree/dev); iraclis (https://github.com/uclexoplanets/Iraclis); juliet (https://github.com/nespinoza/juliet); chromatic
(https://github.com/zkbt/chromatic); chromatic_fitting
(https://github.com/catrionamurray/chromatic_fitting); ExoTiC-LD54, 121
(https://github.com/Exo-TiC/ExoTiC-LD); ExoTETHyS122 (https://github.com/uclexoplanets/ExoTETHyS); PICASO88,89 (https://github.com/natashabatalha/picaso); Virga94, 95
(https://github.com/natashabatalha/virga); CHIMERA (https://github.com/mrline/CHIMERA);
PyMultiNest (https://github.com/JohannesBuchner/PyMultiNest); MultiNest
(https://github.com/JohannesBuchner/MultiNest)The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy. However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality. Here, we present the transmission spectrum of WASP-39 b obtained using the SOSS mode of the NIRISS instrument on JWST. This spectrum spans 0.6â2.8m in wavelength and reveals multiple water absorption bands, the potassium resonance doublet, and signatures of clouds. The precision and broad wavelength coverage of NIRISS-SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy element enhancement (âmetallicityâ) of ~10â30x the solar value, a sub-solar carbon-to-oxygen (C/O) ratio, and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-gray clouds with inhomogeneous coverage of the planetâs terminator.Leverhulme TrustUK Research and Innovatio
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Early Release Science of the exoplanet WASP-39b with JWST NIRSpec G395H
This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this recordData Availability:
The data used in this paper are associated with JWST program ERS 1366 (observation #4) and
are available from the Mikulski Archive for Space Telescopes (https://mast.stsci.edu). Science
data processing version (SDP_VER) 2022_2a generated the uncalibrated data that we
downloaded from MAST. We used JWST Calibration Pipeline software version (CAL_VER)
1.5.3 with modifications described in the text. We used calibration reference data from context
(CRDS_CTX) 0916, except as noted in the text. All the data and models presented in this
publication can be found at 10.5281/zenodo.7185300.Code Availability:
The codes used in this publication to extract, reduce and analyze the data are as follows;
STScI JWST Calibration pipeline45 (https://github.com/spacetelescope/jwst), Eureka!53
(https://eurekadocs.readthedocs.io/en/latest/), ExoTiC-JEDI47 (https://github.com/ExoTiC/ExoTiC-JEDI), juliet71 (https://juliet.readthedocs.io/en/latest/), Tiberius15,49,50,
transitspectroscopy51 (https://github.com/nespinoza/transitspectroscopy). In addition, these
made use of batman65 (http://lkreidberg.github.io/batman/docs/html/index.html), celerite86
(https://celerite.readthedocs.io/en/stable/), chromatic (https://zkbt.github.io/chromatic/),
Dynesty72 (https://dynesty.readthedocs.io/en/stable/index.html), emcee69
(https://emcee.readthedocs.io/en/stable/), exoplanet83 (https://docs.exoplanet.codes/en/latest/),
ExoTEP75â77, ExoTHETyS79 (https://github.com/ucl-exoplanets/ExoTETHyS), ExoTiCISM57 (https://github.com/Exo-TiC/ExoTiC-ISM), ExoTiC-LD58 (https://exoticld.readthedocs.io/en/latest/), george68 (https://george.readthedocs.io/en/latest/) JAX82
(https://jax.readthedocs.io/en/latest/), LMFIT70 (https://lmfit.github.io/lmfit-py/),
Pylightcurve78 (https://github.com/ucl-exoplanets/pylightcurve), Pymc3138
(https://docs.pymc.io/en/v3/index.html) and Starry84 (https://starry.readthedocs.io/en/latest/),
each of which use the standard python libraries astropy139,140, matplotlib141, numpy142,
pandas143, scipy64 and xarray144. The atmospheric models used to fit the data can be found at
ATMO[Tremblin2015,Drummond2016,Goyal2018,Goyal2020]88â91, PHOENIX92â94,
PICASO98,99 (https://natashabatalha.github.io/picaso/), Virga98,107
(https://natashabatalha.github.io/virga/), and gCMCRT115
(https://github.com/ELeeAstro/gCMCRT).Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems. Access to an exoplanetâs chemical inventory requires high precision observations, often inferred from individual molecular detections with low-resolution space-based and high-resolution ground-based facilities. Here we report the medium-resolution (Râ600) transmission spectrum of an exoplanet atmosphere between 3â5 ÎŒm covering multiple absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST NIRSpec G395H. Our observations achieve 1.46Ă
photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO2 (28.5Ï
) and H2O (21.5Ï
), and identify SO2 as the source of absorption at 4.1 Ό
m (4.8Ï
). Best-fit atmospheric models range between 3Ă
and 10Ă
solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO2, underscore the importance of characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec G395H as an excellent mode for time series observations over this critical wavelength range.Science and Technology Facilities Council (STFC)UKR
Structures of Binary C<sub>60</sub>âC<sub>84</sub> Fullerene Clusters<sup>â </sup>
A systematic study of the potential energy global minimum (GM) structures of model binary fullerene clusters of compositions (C-60)n(C-84)(N-n), N 18
Self-assembly and structural behavior of a model rigid C60-terminated thiolate on Au(111)
We have constructed a potential energy function to model the self-assembly of rigid C-60-terminated thiolates on Au(1 1 1). This potential was used to carry out Monte Carlo simulations over a range of temperatures and surface coverage. We find the intermolecular attraction between the C-60 moieties leads to facile self-assembly. At low coverage, the molecules bind in a lying down phase; at higher coverage both lying down and standing up molecules coexist. The strong interaction between C-60 and the metal hinders the formation of highly ordered domain
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