We aim to see if the difference between equilibrium and disequilibrium chemistry is observable in the atmospheres of transiting planets by the James Webb Space Telescope (JWST). We perform a case ...study comparing the dayside emission spectra of three planets like HD 189733b, WASP-80b, and GJ 436b, in and out of chemical equilibrium at two metallicities each. These three planets were chosen because they span a large range of planetary masses and equilibrium temperatures, from hot and Jupiter-sized to warm and Neptune-sized. We link the one-dimensional disequilibrium chemistry model from Venot et al. (2012), in which thermochemical kinetics, vertical transport, and photochemistry are taken into account, to the one-dimensional, pseudo line-by-line radiative transfer model, Pyrat bay, developed especially for hot Jupiters, and then simulate JWST spectra using PandExo for comparing the effects of temperature, metallicity, and radius. We find the most significant differences from 4 to 5 m due to disequilibrium from CO and CO2 abundances, and also H2O for select cases. Our case study shows a certain "sweet spot" of planetary mass, temperature, and metallicity where the difference between equilibrium and disequilibrium is observable. For a planet similar to WASP-80b, JWST's NIRSpec G395M can detect differences due to disequilibrium chemistry with one eclipse event. For a planet similar to GJ 436b, the observability of differences due to disequilibrium chemistry is possible at low metallicity given five eclipse events, but not possible at the higher metallicity.
Abstract
We develop and disseminate effective point-spread functions and geometric-distortion solutions for high-precision astrometry and photometry with the JWST NIRISS instrument. We correct field ...dependencies and detector effects, and assess the quality and the temporal stability of the calibrations. As a scientific application and validation, we study the proper motion (PM) kinematics of stars in the JWST calibration field near the Large Magellanic Cloud (LMC) center, comparing to a first-epoch Hubble Space Telescope (HST) archival catalog with a 16 yr baseline. For stars with
G
∼ 20, the median PM uncertainty is ∼13
μ
as yr
−1
(3.1 km s
−1
), better than Gaia DR3 typically achieves for its very best-measured stars. We kinematically detect the known star cluster OGLE-CL LMC 407, measure its absolute PM for the first time, and show how this differs from other LMC populations. The inferred cluster dispersion sets an upper limit of 24
μ
as yr
−1
(5.6 km s
−1
) on systematic uncertainties. Red-giant-branch stars have a velocity dispersion of 33.8 ± 0.6 km s
−1
, while younger blue populations have a narrower velocity distribution, but with a significant kinematical substructure. We discuss how this relates to the larger velocity dispersions inferred from Gaia DR3. These results establish JWST as capable of state-of-the-art astrometry, building on the extensive legacy of HST. This is the first paper in a series by our JWST Telescope Scientist Team, in which we will use Guaranteed Time Observations to study the PM kinematics of various stellar systems in the Local Group.
ABSTRACT
We present an optical transmission spectrum of the hot Jupiter WASP-101b. We observed three primary transits with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph, covering ...a wavelength range from 0.3 to 1 $\mu$m. The observations suffer from significant systematics that we model using Gaussian Processes. Kernel selection for the Gaussian Processes is performed in a data-driven approach through Bayesian model comparison. We find a flat and featureless transmission spectrum, corroborating a previous measurement obtained with HST/Wide-Field Camera 3 in the 1–1.7 $\mu$m range. The spectrum is consistent with high-altitude clouds located at less than 100 $\mu$bar. This cloud layer completely blocks our view into deeper parts of the atmosphere and makes WASP-101b the cloudiest gas giant observed so far. We compute a series of temperature-pressure profiles for WASP-101b and compare these to condensation curves for cloud particles, which match clouds composed of silicates. We also include 13 transits observed with Transiting Exoplanet Survey Satellite and use these to refine system parameters.
We present a uniform analysis of transit observations from the Hubble Space Telescope and Spitzer Space Telescope of two warm gas giants orbiting K-type stars—WASP-29b and WASP-80b. The transmission ...spectra, which span 0.4–5.0μm, are interpreted using a suite of chemical equilibrium PLATON atmospheric retrievals. Both planets show evidence of significant aerosol opacity along the day–night terminator. The spectrum of WASP-29b is flat throughout the visible and near-infrared, suggesting the presence of condensate clouds extending to low pressures. The lack of spectral features hinders our ability to constrain the atmospheric metallicity and C/O ratio. In contrast, WASP-80b shows a discernible, albeit muted H2O absorption feature at 1.4μm, as well as a steep optical spectral slope that is caused by fine-particle aerosols and/or contamination from unocculted spots on the variable host star. WASP-80b joins the small number of gas-giant exoplanets that show evidence for enhanced atmospheric metallicity: the transmission spectrum is consistent with metallicities ranging from∼30–100 times solar in the case of cloudy limbs to a few hundred times solar in the cloud-free scenario. In addition to the detection of water, we infer the presence of CO2in the atmosphere of WASP-80b based on the enhanced transit depth in the Spitzer 4.5μm bandpass. From a complementary analysis of Spitzer secondary eclipses, we find that the day side emission from WASP-29b and WASP-80b is consistent with brightness temperatures of 937±48 and 851±14 K, respectively, indicating relatively weak day–night heat transport and low Bond albedo.
Abstract
Here we present a thermal emission spectrum of WASP-79b, obtained via Hubble Space Telescope Wide Field Camera 3 G141 observations as part of the PanCET program. As we did not observe the ...ingress or egress of WASP-79b’s secondary eclipse, we consider two scenarios: a fixed mid-eclipse time based on the expected occurrence time, and a mid-eclipse time as a free parameter. In both scenarios, we can measure thermal emission from WASP-79b from 1.1 to 1.7
μ
m at 2.4
σ
confidence consistent with a 1900 K brightness temperature for the planet. We combine our observations with Spitzer dayside photometry (3.6 and 4.5
μ
m) and compare these observations to a grid of atmospheric forward models that span a range of metallicities, carbon-to-oxygen ratios, and recirculation factors. Given the strength of the planetary emission and the precision of our measurements, we found a wide range of forward models to be consistent with our data. The best-match equilibrium model suggests that WASP-79b’s dayside has a solar metallicity and carbon-to-oxygen ratio, alongside a recirculation factor of 0.75. Models including significant H
−
opacity provide the best match to WASP-79b’s emission spectrum near 1.58
μ
m. However, models featuring high-temperature cloud species—formed via vigorous vertical mixing and low sedimentation efficiencies—with little day-to-night energy transport also match WASP-79b’s emission spectrum. Given the broad range of equilibrium chemistry, disequilibrium chemistry, and cloudy atmospheric models consistent with our observations of WASP-79b’s dayside emission, further observations will be necessary to constrain WASP-79b’s dayside atmospheric properties.
Abstract
Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise ...chemical abundance constraints. We present the first optical to infrared (0.3−5
μ
m) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1
σ
detection of Na
i
absorption at 0.59
μ
m, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4
μ
m is tentatively attributed to SiH at 2.1
σ
confidence. Our retrieval analyses are consistent with a cloud-free atmosphere without significant contamination from stellar heterogeneities. We simulate James Webb Space Telescope (JWST) observations, for a combination of instrument modes, to assess the atmospheric characterization potential of WASP-62b. We demonstrate that JWST can conclusively detect Na, H
2
O, FeH, NH
3
, CO, CO
2
, CH
4
, and SiH within the scope of its Early Release Science (ERS) program. As the only transiting giant planet currently known in the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant exoplanet for detailed atmospheric characterization in the James Webb era.
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 mounted on the Hubble ...Space Telescope, combined with Spitzer/Infrared Array Camera photometry at 3.6 and 4.5 m. 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. We bin the data in 38 spectrophotometric light curves from 0.29 to 4.5 m 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 confidence, but we find 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 m. 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.
Abstract
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 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
μ
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 6.6
σ
when using a template with only
12
C
16
O lines. The CCF significance of the CO signal increases to 7.5
σ
when including in the template lines from additional CO isotopologues, with the largest contribution being from
13
C
16
O. 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.
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