A Comparison of Simulated JWST Observations Derived from Equilibrium and Non-equilibrium Chemistry Models of Giant Exoplanets

Blumenthal, Sarah D.; Mandell, Avi M.; Hébrard, Éric; Batalha, Natasha E.; Cubillos, Patricio; Rugheimer, Sarah; Wakeford, Hannah R.

doi:10.3847/1538-4357/aa9e51

Cited by 21 publications

(24 citation statements)

References 77 publications

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“…For example, the metallicity posterior shifted by 0.1σ for the transit retrieval and 0.5σ for the eclipse retrieval; the C/O ratio posterior shifted by 0.06σ for both transit and eclipse retrievals. We conclude that the effects of disequilibrium chemistry are below our detection threshold, in good agreement with the predictions of the 1D models from Venot et al (2012) and Blumenthal et al (2018).…”

Section: Aerosol Propertiessupporting

confidence: 85%

“…Their Figure 10 shows that the disequilibrium-induced brightness temperature discrepancy is at most several Kelvin (less than 1%), while the transit radius discrepancy is at most ∼30 ppm. Blumenthal et al (2018) also model the emission spectrum under equilibrium and nonequilibrium conditions, finding no detectable difference even with JWST (their Figure 3). Other studies report changes in abundance as a result of disequilibrium chemistry, but do not compare the resulting spectra to the equilibrium model predictions.…”

Section: Aerosol Propertiesmentioning

confidence: 96%

“…HD 189733b lies in a regime where disequilibrium chemistry may be important. Multiple studies have explored disequilibrium chemistry on this planet (Line et al 2010;Venot et al 2012;Moses et al 2013;Agúndez et al 2014;Blumenthal et al 2018;Steinrueck et al 2019). Venot et al (2012) considered 1D models with both UV photochemistry and vertical mixing, and found negligible differences in the resulting transmission and emission spectra as compared to equilibrium models.…”

Section: Aerosol Propertiesmentioning

confidence: 99%

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PLATON II: New Capabilities and a Comprehensive Retrieval on HD 189733b Transit and Eclipse Data

Zhang

Chachan

Kempton

et al. 2020

ApJ

110

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Recently, we introduced PLanetary Atmospheric Tool for Observer Noobs (PLATON), a Python package that calculates model transmission spectra for exoplanets and retrieves atmospheric characteristics based on observed spectra. We now expand its capabilities to include the ability to compute secondary eclipse depths. We have also added the option to calculate models using the correlated-k method for radiative transfer, which improves accuracy without sacrificing speed. Additionally, we update the opacities in PLATON-many of which were generated using old or proprietary line lists-using the most recent and complete public line lists. These opacities are made available at R=1000 and R=10,000 over the 0.3 − −30 µm range, and at R=375,000 in select near IR bands, making it possible to utilize PLATON for ground-based high resolution cross correlation studies. To demonstrate PLATON's new capabilities, we perform a retrieval on published HST and Spitzer transmission and emission spectra of the archetypal hot Jupiter HD 189733b. This is the first joint transit and secondary eclipse retrieval for this planet in the literature, as well as the most comprehensive set of both transit and eclipse data assembled for a retrieval to date. We find that these high signal-to-noise data are well-matched by atmosphere models with a C/O ratio of 0.66 +0.05 −0.09 and a metallicity of 12 +8 −5 times solar where the terminator is dominated by extended nanometer-sized haze particles at optical wavelengths. These are among the smallest uncertainties reported to date for an exoplanet, demonstrating both the power and the limitations of HST and Spitzer exoplanet observations.

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Section: Aerosol Propertiessupporting

confidence: 85%

Section: Aerosol Propertiesmentioning

confidence: 96%

Section: Aerosol Propertiesmentioning

confidence: 99%

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PLATON II: New Capabilities and a Comprehensive Retrieval on HD 189733b Transit and Eclipse Data

Zhang

Chachan

Kempton

et al. 2020

ApJ

110

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“…On the opposite, scattered spectra can inform us on the stability and the redundancy in the information content of Ariel spectra. Previous studies have used both types to simulate observations by future telescopes (Barstow et al 2012;Tinetti et al 2015Tinetti et al , 2018Feng et al 2016Feng et al , 2018Rocchetto et al 2016;Batalha et al 2017;Mollière et al 2017;Blumenthal et al 2018;Changeat et al 2019aChangeat et al , 2019bEdwards et al 2019b;Lustig-Yaeger et al 2019). Feng et al (2018) results predicted that the retrieved uncertainties should be similar in both scattered and unscattered runs but that the retrieved mean could be different.…”

Section: The Ability Of Ariel To Reveal Chemical Trends In Exoplanetmentioning

confidence: 99%

Alfnoor: A Retrieval Simulation of the Ariel Target List

Changeat

Al-Refaie

Mugnai

et al. 2020

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In this work, we present Alfnoor, a dedicated tool optimized for population studies of exoplanet atmospheres. Alfnoor combines the latest version of the retrieval algorithm, TauREx 3, with the instrument noise simulator ArielRad and enables the simultaneous retrieval analysis of a large sample of exo-atmospheres. We applied this tool to the Ariel list of planetary candidates and focus on hydrogen dominated, cloudy atmospheres observed in transit with the Tier-2 mode (medium Ariel resolution). As a first experiment, we randomized the abundancesranging from 10 −7 to 10 −2-of the trace gases, which include H 2 O, CH 4 , CO, CO 2 , and NH 3. This exercise allowed us to estimate the detection limits for Ariel Tier-2 and Tier-3 modes when clouds are present. In a second experiment, we imposed an arbitrary trend between a chemical species and the effective temperature of the planet. A last experiment was run requiring molecular abundances being dictated by equilibrium chemistry at a certain temperature. Our results demonstrate the ability of Ariel Tier-2 and Tier-3 surveys to reveal trends between the chemistry and associated planetary parameters. Future work will focus on eclipse data, on atmospheres heavier than hydrogen, and will be applied also to other observatories.

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“…However, these two studies did not attempt detailed predictions of the impact of disequilibrium processes on the spectra of KELT-9. Finally, a possibility to study disequilibrium chemistry in atmospheres of three planets (HD 189733 b, WASP-80 b, and GJ 436 b, all having T eq < 1200 K) with future space missions was carried out in Blumenthal et al (2018), concluding that, for example, with the James Webb Space Telescope (JWST) it will be possible to robustly constrain the difference between equilibrium and disequilibrium chemistry. Analyzing chemistry in HJs provides an important test for existing kinetic models as they include many poorly known parameters (e.g., turbulent diffusion coefficients, photodissociation cross-section, reaction rate coefficients, and choice of the kinetic network.).…”

Section: Introductionmentioning

confidence: 99%

Stellar impact on disequilibrium chemistry and observed spectra of hot Jupiter atmospheres

Shulyak

Lara

Rengel

et al. 2020

A&A

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Aims. We study the effect of disequilibrium processes (photochemistry and vertical transport) on mixing ratio profiles of neutral species and on the simulated spectra of a hot Jupiter exoplanet that orbits stars of various spectral types. We additionally address the impact of stellar activity that should be present, to various degrees, in all stars with convective envelopes. Methods. We used the VULCAN chemical kinetic code to compute number densities of species in irradiated planetary atmospheres. The temperature-pressure profile of the atmosphere was computed with the HELIOS code. We also utilized the τ-REx forward model to predict the spectra of planets in primary and secondary eclipses. In order to account for the stellar activity, we made use of the observed solar extreme ultraviolet (XUV) spectrum taken from Virtual Planetary Laboratory as a proxy for an active sun-like star. Results. We find large changes in the mixing ratios of most chemical species in planets orbiting A-type stars, which radiate strong XUV flux thereby inducing a very effective photodissociation. For some species, these changes can propagate very deep into the planetary atmosphere to pressures of around 1 bar. To observe disequilibrium chemistry we favor hot Jupiters with temperatures Teq = 1000 K and ultra-hot Jupiters, with Teq ≈ 3000 K,which also have temperature inversion in their atmospheres. On the other hand, disequilibrium calculations predict no noticeable changes in spectra of planets with intermediate temperatures. We also show that stellar activity similar to that of the modern Sun drives important changes in mixing ratio profiles of atmospheric species. However, these changes take place at very high atmospheric altitudes and thus do not affect predicted spectra. Finally, we estimate that the effect of disequilibrium chemistry in planets orbiting nearby bright stars could be robustly detected and studied with future missions with spectroscopic capabilities in infrared such as James Webb Space Telescope and ARIEL.

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A Comparison of Simulated JWST Observations Derived from Equilibrium and Non-equilibrium Chemistry Models of Giant Exoplanets

Cited by 21 publications

References 77 publications

PLATON II: New Capabilities and a Comprehensive Retrieval on HD 189733b Transit and Eclipse Data

PLATON II: New Capabilities and a Comprehensive Retrieval on HD 189733b Transit and Eclipse Data

Alfnoor: A Retrieval Simulation of the Ariel Target List

Stellar impact on disequilibrium chemistry and observed spectra of hot Jupiter atmospheres

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