56 research outputs found
Coupling haze and cloud microphysics in WASP-39b's atmosphere based on JWST observations
We present a study on the coupling of haze and clouds in the atmosphere of
WASP-39b. We developed a cloud microphysics model simulating the formation of
Na2S and MgSiO3 condensates over photochemical hazes in gas giant atmospheres.
We apply this model to WASP-39b, recently observed with the JWST to study how
these heterogeneous components may affect the transit spectrum. We simulate
both morning and evening terminators independently and average their transit
spectra. While MgSiO3 formation has negligible impact on the spectrum, Na2S
condensates produce gray opacities in the water band, in agreement with HST and
JWST observations. Moreover, the formation of Na2S on the morning side depletes
the atmosphere of its sodium content, decreasing the strength of the Na line.
Combining morning and evening profiles results in a good fit of the Na
observations. These nominal results assume a small Na2S/haze contact angle
(5.7{\deg}). Using a larger value (61{\deg}) reduces the cloud density and
opacity, but the effect on the Na profile and spectral line remains identical.
In addition, the presence of haze in the upper atmosphere reproduces the
UV-visible slope observed in the HST and VLT data and contributes to the
opacity between the water bands at wavelengths below 2 microns. The averaged
spectra are rather insensitive to the variation of eddy diffusion and haze mass
flux tested in this study, though the UV-visible slope, probing the haze layer
above the clouds, is affected. Finally, our disequilibrium chemistry model,
including photochemistry, reproduces the SO2 and CO2 absorption features
observed.Comment: 19 pages, 16 figure
A physically derived eddy parameterization for giant planet atmospheres with application on hot-Jupiter atmospheres
We present a parameterization for the eddy diffusion profile of gas giant
exoplanets based on physical phenomena and we explore how the parameterized
eddy profile impacts the chemical composition, the thermal structure, the haze
microphysics, and the transit spectra of 8 hot-Jupiters. Our eddy
parameterization depends on the planetary intrinsic temperature (T ),
we thus evaluate how the increase of this parameter to values higher than those
typically used (100K) impacts the atmospheric structure and composition.
Our investigation demonstrates that despite the strong impact of T on
the chemical composition of the deep atmosphere, the upper atmosphere is not
affected for T 1300 K owing to high altitude quench levels at these
conditions. Below this threshold, however, the larger atmospheric temperatures
produced by increasing T affect the quenched chemical composition. Our
parameterization depends on two parameters, the eddy magnitude at the
radiative-convective boundary (K) and the corresponding magnitude at the
homopause (K). We demonstrate that, when using common K and
K values among most of the different planet cases studied, we derive
transit spectra consistent with Hubble Space Telescope observations. Moreover,
our simulations show that increasing the eddy profile enhances the
photochemical production of haze particles and reduces their average radius,
thus providing a steeper UV-Visible slope. Finally, we demonstrate for WASP-39b
that the James Webb Space Telescope observations provide improved constraints
for the hazes and clouds and we show that both components seem necessary to
interpret the combined transit spectrum from HST and JWST observations.Comment: 19 pages, 12 figure
Photochemical hazes in sub-Neptunian atmospheres with focus on GJ 1214 b
We study the properties of photochemical hazes in super-Earths/mini-Neptunes
atmospheres with particular focus on GJ1214b. We evaluate photochemical haze
properties at different metallicities between solar and 10000solar.
Within the four orders of magnitude change in metallicity, we find that the
haze precursor mass fluxes change only by a factor of 3. This small
diversity occurs with a non-monotonic manner among the different metallicity
cases, reflecting the interaction of the main atmospheric gases with the
radiation field. Comparison with relative haze yields at different
metallicities from laboratory experiments reveals a qualitative similarity with
our theoretical calculations and highlights the contributions of different gas
precursors. Our haze simulations demonstrate that higher metallicity results
into smaller average particle sizes. Metallicities at and above
100solar with haze formation yields of 10 provide enough haze
opacity to satisfy transit observation at visible wavelengths and obscure
sufficiently the HO molecular absorption features between 1.1 m and
1.7 m. However, only the highest metallicity case considered
(10000solar) brings the simulated spectra into closer agreement with
transit depths at 3.6 m and 4.5 m indicating a high contribution of
CO/CO in GJ1214b's atmosphere. We also evaluate the impact of aggregate
growth in our simulations, in contrast to spherical growth, and find that the
two growth modes provide similar transit signatures (for D=2), but with
different particle size distributions. Finally, we conclude that the simulated
haze particles should have major implications for the atmospheric thermal
structure and for the properties of condensation clouds
Titan Haze
The Titan haze exerts a dominating influence on surface visibility and atmospheric radiative heating at optical and near-infrared wavelengths and our desire to understand surface composition and atmospheric dynamics provides a strong motivation to study the properties of the haze. Prior to the Cassini/Huygens missions the haze was known to be global in extent, with a hemispheric contrast asymmetry, with a complicated structure in the polar vortex region poleward of about 55 deg latitude, and with a distinct layer near 370 km altitude outside of the polar vortex at the time of the Voyager 2 flyby. The haze particles measured by the Pioneer and Voyager spacecraft were both highly polarizing and strongly forward scattering, a combination that seems to require an aggregation of small (several tens of nm radius) primary particles. These same properties were seen in the Cassini orbiter and Huygens Probe data. The most extensive set of optical measurements were made inside the atmosphere by the Descent Imager/Spectral Radiometer (DISR) instrument on the Huygens Probe. At the probe location as determined by the DISR measurements the average haze particle contained about 3000 primary particles whose radius is about 40 nm. Three distinct vertical regions were seen in the DISR data with differing particle properties. Refractive indices of the particles in the main haze layer resemble those reported by Khare et al. between O.3S and about 0.7 micron but are more absorbing than the Khare et al. results between 0.7 micron and the long-wavelength limit of the DISR spectra at 1.6 micron. These and other results are described by Tomasko et al., and a broader summary of results was given by Tomasko and West,. New data continue to stream in from the Cassini spacecraft. New data analyses and new laboratory and model results continue to move the field forward. Titan's 'detached' haze layer suffered a dramatic drop in altitude near equinox in 2009 with implications for the circulation and seasonal change in the stratosphere. The book chapter associated with this talk will also present new material on thermal-infrared data analysis and on new developments in laboratory work and haze microphysical modeling
Detection of Na, K, and H<sub>2</sub>O in the hazy atmosphere of WASP-6b
We present new observations of the transmission spectrum of the hot Jupiter WASP-6b both from the ground with the Very Large Telescope FOcal Reducer and Spectrograph (FORS2) from 0.45 to 0.83 μm, and space with the Transiting Exoplanet Survey Satellite from 0.6 to 1.0 μm and the Hubble Space Telescope (HST) Wide Field Camera 3 from 1.12 to 1.65 μm. Archival data from the HST Space Telescope Imaging Spectrograph (STIS) and Spitzer are also re-analysed on a common Gaussian process framework, of which the STIS data show a good overall agreement with the overlapping FORS2 data. We also explore the effects of stellar heterogeneity on our observations and its resulting implications towards determining the atmospheric characteristics of WASP-6b. Independent of our assumptions for the level of stellar heterogeneity we detect Na I, K I, and H2O absorption features and constrain the elemental oxygen abundance to a value of [O/H] ≃ -0.9 ± 0.3 relative to solar. In contrast, we find that the stellar heterogeneity correction can have significant effects on the retrieved distributions of the [Na/H] and [K/H] abundances, primarily through its degeneracy with the sloping optical opacity of scattering haze species within the atmosphere. Our results also show that despite this presence of haze, WASP-6b remains a favourable object for future atmospheric characterization with upcoming missions such as the James Webb Space Telescope
The Hubble Space Telescope PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab
We present a 0.3-5 μm transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 Å, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planet's atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of , a thick cloud deck, enhanced Rayleigh scattering, and ∼10× solar abundance. We find log() = , and compare this measurement with the mass-metallicity relation derived for the solar system
- …