Thermal and Kinetic Impact of CO, CO<sub>2</sub>, and H<sub>2</sub>O on the Postoxidation of IC-Engine Exhaust Gases

Anderlohr, Jörg; Cruz, A. Pires da; Bounaceur, Roda; Battin‐Leclerc, Frédérique

doi:10.1080/00102200903190844

Cited by 24 publications

(22 citation statements)

References 19 publications

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“…Battin-Leclerc et al 2006;Bounaceur et al 2007;Anderlohr et al 2010;Bounaceur et al 2010;Wang et al 2010). Obviously, it is not possible to describe all these validations in detail, but we can mention, for instance, the very recent work of Dirrenberger et al (2011) who has studied the laminar burning velocity of several mixtures including air, hydrogen, and components of natural gas experimentally and modeled it with success.…”

Section: -C 2 Reaction Basementioning

confidence: 99%

A chemical model for the atmosphere of hot Jupiters

Venot

Hébrard

Agúndez

et al. 2012

A&A

224

555

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Context. The atmosphere of hot Jupiters can be probed by primary transit and secondary eclipse spectroscopy. Owing to the intense UV irradiation, mixing, and circulation, their chemical composition is maintained out of equilibrium and must be modeled with kinetic models. Aims. Our purpose is to release a chemical network and the associated rate coefficients, developed for the temperature and pressure range relevant to hot Jupiters atmospheres. Using this network, we study the vertical atmospheric composition of the two hot Jupiters (HD 209458b and HD 189733b) with a model that includes photolyses and vertical mixing, and we produce synthetic spectra. Methods. The chemical scheme has been derived from applied combustion models that were methodically validated over a range of temperatures and pressures typical of the atmospheric layers influencing the observations of hot Jupiters. We compared the predictions obtained from this scheme with equilibrium calculations, with different schemes available in the literature that contain N-bearing species, and with previously published photochemical models. Results. Compared to other chemical schemes that were not subjected to the same systematic validation, we find significant differences whenever nonequilibrium processes take place (photodissociations or vertical mixing). The deviations from the equilibrium, hence the sensitivity to the network, are larger for HD 189733b, since we assume a cooler atmosphere than for HD 209458b. We found that the abundances of NH 3 and HCN can vary by two orders of magnitude depending on the network, demonstrating the importance of comprehensive experimental validation. A spectral feature of NH 3 at 10.5 μm is sensitive to these abundance variations and thus to the chemical scheme.Conclusions. Due to the influence of the kinetics, we recommend using a validated scheme to model the chemistry of exoplanet atmospheres. The network we release is robust for temperatures within 300-2500 K and pressures from 10 mbar up to a few hundred bars, for species made of C, H, O, and N. It is validated for species up to 2 carbon atoms and for the main nitrogen species (NH 3 , HCN, N 2 , NO x ). Although the influence of the kinetic scheme on the hot Jupiters spectra remains within the current observational error bars (with the exception of NH 3 ), it will become more important for atmospheres that are cooler or subjected to higher UV fluxes, because they depart more from equilibrium.

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Section: -C 2 Reaction Basementioning

confidence: 99%

A chemical model for the atmosphere of hot Jupiters

Venot

Hébrard

Agúndez

et al. 2012

A&A

224

555

View full text Add to dashboard Cite

show abstract

“…In Venot et al (2015), it was shown that a more sophisticated chemical scheme including species with up to six carbon atoms produces comparable results, and that the simpler scheme can reliably model atmospheres with C/O ratios above 1. The scheme has been developed with combustion specialists and validated by experiments conducted in a wide range of temperatures (300-2500 K) and pressures (0.01-100 bar; e.g., Battin-Leclerc et al 2006;Bounaceur et al 2007Bounaceur et al , 2010Anderlohr et al 2010;Wang et al 2010).…”

Section: Ab Initio Chemical Simulationsmentioning

confidence: 99%

Detection of an Atmosphere Around the Super-Earth 55 Cancri E

Tsiaras

Rocchetto

Waldmann

et al. 2016

ApJ

247

238

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We report the analysis of two new spectroscopic observations in the near-infrared of the super-Earth 55 Cancri e, obtained with the WFC3 camera on board the Hubble Space Telescope. 55 Cancri e orbits so close to its parent star that temperatures much higher than 2000 K are expected on its surface. Given the brightness of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length and a very high scanning speed. We use our specialized pipeline to take into account systematics introduced by these observational parameters when coupled with the geometrical distortions of the instrument. We measure the transit depth per wavelength channel with an average relative uncertainty of 22 ppm per visit and find modulations that depart from a straight line model with a 6σ confidence level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably hydrogen-rich. Our fully Bayesian spectral retrieval code,  -REx, has identified HCN to be the most likely molecular candidate able to explain the features at 1.42 and 1.54 μm. While additional spectroscopic observations in a broader wavelength range in the infrared will be needed to confirm the HCN detection, we discuss here the implications of such a result. Our chemical model, developed with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic than previously thought.

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“…These models have been used to study exoplanets Venot et al 2014Tsiaras et al 2016), as well as solar system giant planets (Cavalié et al 2014;Mousis et al 2014). The chemical scheme has been developed with combustion specialists and validated in a wide range of pressures (0.001-100 bars) and temperatures (300-2500 K), making this model one of the currently most reliable chemical schemes (Battin-Leclerc et al 2006;Bounaceur et al 2007;Anderlohr et al 2010;Wang et al 2010). showed that the use of more complete chemical models, including species with up to six carbon atoms, has little effect on the synthetic spectra.…”

Section: Chemical Modelsmentioning

confidence: 99%

Exploring Biases of Atmospheric Retrievals in Simulated JWST Transmission Spectra of Hot Jupiters

Rocchetto

Waldmann

Venot

et al. 2016

ApJ

107

113

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With a scheduled launch in 2018 October, the James Webb Space Telescope ( JWST) is expected to revolutionize the field of atmospheric characterization of exoplanets. The broad wavelength coverage and high sensitivity of its instruments will allow us to extract far more information from exoplanet spectra than what has been possible with current observations. In this paper, we investigate whether current retrieval methods will still be valid in the era of JWST, exploring common approximations used when retrieving transmission spectra of hot Jupiters. To assess biases, we use 1D photochemical models to simulate typical hot Jupiter cloud-free atmospheres and generate synthetic observations for a range of carbon-to-oxygen ratios. Then, we retrieve these spectra using TauREx, a Bayesian retrieval tool, using two methodologies: one assuming an isothermal atmosphere, and one assuming a parameterized temperature profile. Both methods assume constant-with-altitude abundances. We found that the isothermal approximation biases the retrieved parameters considerably, overestimating the abundances by about one order of magnitude. The retrieved abundances using the parameterized profile are usually within 1σ of the true state, and we found the retrieved uncertainties to be generally larger compared to the isothermal approximation. Interestingly, we found that by using the parameterized temperature profile we could place tight constraints on the temperature structure. This opens the possibility of characterizing the temperature profile of the terminator region of hot Jupiters. Lastly, we found that assuming a constant-with-altitude mixing ratio profile is a good approximation for most of the atmospheres under study.

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Thermal and Kinetic Impact of CO, CO₂, and H₂O on the Postoxidation of IC-Engine Exhaust Gases

Cited by 24 publications

References 19 publications

A chemical model for the atmosphere of hot Jupiters

A chemical model for the atmosphere of hot Jupiters

Detection of an Atmosphere Around the Super-Earth 55 Cancri E

Exploring Biases of Atmospheric Retrievals in Simulated JWST Transmission Spectra of Hot Jupiters

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Thermal and Kinetic Impact of CO, CO2, and H2O on the Postoxidation of IC-Engine Exhaust Gases

Cited by 24 publications

References 19 publications

A chemical model for the atmosphere of hot Jupiters

A chemical model for the atmosphere of hot Jupiters

Detection of an Atmosphere Around the Super-Earth 55 Cancri E

Exploring Biases of Atmospheric Retrievals in Simulated JWST Transmission Spectra of Hot Jupiters

Contact Info

Product

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About

Thermal and Kinetic Impact of CO, CO₂, and H₂O on the Postoxidation of IC-Engine Exhaust Gases