A Consistent Retrieval Analysis of 10 Hot Jupiters Observed in Transmission

Barstow, Joanna K.; Aigrain, S.; Irwin, Patrick; Sing, David K.

doi:10.3847/1538-4357/834/1/50

Cited by 249 publications

(299 citation statements)

References 59 publications

(134 reference statements)

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“…Sing et al (2013) found that the best-fit model for WASP-12b transmission spectroscopy was Mie scattering by an aluminum-oxide (Al 2 O 3 ) haze. Barstow et al (2017) found that an optically thick Rayleigh scattering aerosol with a 0.01 mbar top pressure best described the transmission observations, but the model poorly described the steep increase in transit depth at optical wavelengths. Schwartz et al (2017) …”

Section: Introductionmentioning

confidence: 93%

The Very Low Albedo of WASP-12b from Spectral Eclipse Observations with Hubble

Bell

Nikolov

Cowan

et al. 2017

ApJL

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We present an optical eclipse observation of the hot Jupiter WASP-12b using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. These spectra allow us to place an upper limit of A 0.064 g < (97.5% confidence level) on the planet's white light geometric albedo across 290-570 nm. Using six wavelength bins across the same wavelength range also produces stringent limits on the geometric albedo for all bins. However, our uncertainties in eclipse depth are ∼40% greater than the Poisson limit and may be limited by the intrinsic variability of the Sun-like host star-the solar luminosity is known to vary at the 10 −4 level on a timescale of minutes. We use our eclipse depth limits to test two previously suggested atmospheric models for this planet: Mie scattering from an aluminum-oxide haze or cloud-free Rayleigh scattering. Our stringent nondetection rules out both models and is consistent with thermal emission plus weak Rayleigh scattering from atomic hydrogen and helium. Our results are in stark contrast with those for the much cooler HD 189733b, the only other hot Jupiter with spectrally resolved reflected light observations; those data showed an increase in albedo with decreasing wavelength. The fact that the first two exoplanets with optical albedo spectra exhibit significant differences demonstrates the importance of spectrally resolved reflected light observations and highlights the great diversity among hot Jupiters.

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Section: Introductionmentioning

confidence: 93%

The Very Low Albedo of WASP-12b from Spectral Eclipse Observations with Hubble

Bell

Nikolov

Cowan

et al. 2017

ApJL

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“…Similar (∼0.1 µm) particle sizes have been found by Pont et al (2013), Lee et al (2014), Sing et al (2015b), who report that they need small cloud particles at high altitudes with sizes between 0.02 and 0.1 µm to reproduce the strong Rayleigh signal observed in the optical and UV of the planets HD 189733b and WASP-31b. The need for submicron-sized cloud particles in hot Jupiters has recently also been pointed out by Barstow et al (2017), at least in certain equilibrium temperature ranges. Pont et al (2013) and Lee et al (2014) find that this small particle cloud layer may be homogeneous over multiple scale heights in HD 189733b.…”

Section: No Yesmentioning

confidence: 99%

“…While it was theorized that muted water features could also be caused by depletion of water (Madhusudhan et al 2014b), or a general depletion of metals in the atmospheres, evidence nowadays seems to point to the presence of clouds (Sing et al 2015a;Iyer et al 2016) or a combination of clouds and metal depletion (Barstow et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Observing transiting planets with JWST

Mollière

Boekel

Bouwman

et al. 2017

A&A

185

250

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Context. The James Webb Space Telescope will enable astronomers to obtain exoplanet spectra of unprecedented precision. The MIRI instrument especially may shed light on the nature of the cloud particles obscuring planetary transmission spectra in the optical and near-infrared. Aims. We provide self-consistent atmospheric models and synthetic JWST observations for prime exoplanet targets in order to identify spectral regions of interest and estimate the number of transits needed to distinguish between model setups. Methods. We select targets that span a wide range of planetary temperatures and surface gravities, ranging from super-Earths to giant planets, that have a high expected signal-to-noise ratio. For all targets, we vary the enrichment, C/O ratio, presence of optical absorbers (TiO/VO), and cloud treatment. We calculate atmospheric structures, emission, and transmission spectra for all targets and use a radiometric model to obtain simulated observations. Further, we analyze JWST's ability to distinguish between various scenarios. Results. We find that in very cloudy planets, such as GJ 1214b, less than ten transits with NIRSpec may be enough to reveal molecular features. Furthermore, the presence of small silicate grains in atmospheres of hot Jupiters may be detectable with a single JWST MIRI transit. For a more detailed characterization of such particles less than ten transits are necessary. Finally, we find that some of the hottest hot Jupiters are well fitted by models which neglect the redistribution of the insolation and harbor inversions, and that 1-4 eclipse measurements with NIRSpec are needed to distinguish between the inversion models.Conclusions. Wet thus demonstrate the capabilities of JWST for solving some of the most intriguing puzzles in current exoplanet atmospheric research. Further, by publishing all models calculated for this study we enable the community to carry out similar studies, as well as retrieval analyses for all planets included in our target list.

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“…That can be due to either clouds (Barstow et al 2017) or low abundance of water vapor . As for correlations, in the top panel of Figure 2, we show the relation between A H and planetary equilibrium temperature.…”

Section: Statistical Correlationsmentioning

confidence: 99%

“…We hypothesize that the dominant effect is the decreasing amount of cloud condensation as the planetary equilibrium temperature increases. To the extent that hotter planets have fewer cloudforming condensate species present in their atmospheres than cooler planets (Kataria et al 2016;Barstow et al 2017), that will tend to produce a positive slope between temperature and A H .…”

Section: Statistical Correlationsmentioning

confidence: 99%

Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

Deming

Knutson

et al. 2017

ApJL

115

108

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Transmission spectroscopy provides a window to study exoplanetary atmospheres, but that window is fogged by clouds and hazes. Clouds and haze introduce a degeneracy between the strength of gaseous absorption features and planetary physical parameters such as abundances. One way to break that degeneracy is via statistical studies. We collect all published HST/WFC3 transit spectra for 1.1-1.65 μm water vapor absorption and perform a statistical study on potential correlations between the water absorption feature and planetary parameters. We fit the observed spectra with a template calculated for each planet using the Exo-transmit code. We express the magnitude of the water absorption in scale heights, thereby removing the known dependence on temperature, surface gravity, and mean molecular weight. We find that the absorption in scale heights has a positive baseline correlation with planetary equilibrium temperature; our hypothesis is that decreasing cloud condensation with increasing temperature is responsible for this baseline slope. However, the observed sample is also intrinsically degenerate in the sense that equilibrium temperature correlates with planetary mass. We compile the distribution of absorption in scale heights, and we find that this distribution is closer to log-normal than Gaussian. However, we also find that the distribution of equilibrium temperatures for the observed planets is similarly log-normal. This indicates that the absorption values are affected by observational bias, whereby observers have not yet targeted a sufficient sample of the hottest planets.

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A Consistent Retrieval Analysis of 10 Hot Jupiters Observed in Transmission

Cited by 249 publications

References 59 publications

The Very Low Albedo of WASP-12b from Spectral Eclipse Observations with Hubble

The Very Low Albedo of WASP-12b from Spectral Eclipse Observations with Hubble

Observing transiting planets with JWST

Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

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