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

Shulyak, D.; Lara, L. M.; Rengel, Miriam; Nèmec, Nina-Elisabeth

doi:10.1051/0004-6361/201937210

Cited by 22 publications

(21 citation statements)

References 101 publications

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“…To calculate the LTE transmission profiles we employed the τ-REx (Tau Retrieval for Exoplanets) forward model (Waldmann et al 2015a). We used an extended version of the original package, which now includes additional continuum opacity sources relevant for the high atmospheric temperatures of KELT-9b, as described in Shulyak et al (2020).…”

Section: Relevance Of Nlte Effectsmentioning

confidence: 99%

“…Because LLMODELS is a module structured code, we turned some of its modules into numerical libraries and loaded them into τ-REx to compute continuum opacity additional to those described in Shulyak et al (2020). In particular, we calculated opacities due to HI, He, and various metals, which contribute a small, but non-negligible, ∼8% to the total transmission depth at the wavelengths around the Hα line.…”

Section: Relevance Of Nlte Effectsmentioning

confidence: 99%

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A data-driven approach to constraining the atmospheric temperature structure of the ultra-hot Jupiter KELT-9b

Fossati

Shulyak

Sreejith

et al. 2020

A&A

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Context. Observationally constraining the atmospheric temperature-pressure (TP) profile of exoplanets is an important step forward for improving planetary atmosphere models, thus further enabling one to place the detection of spectral features and the measurement of atomic and molecular abundances through transmission and emission spectroscopy on solid ground. Aims. The aim is to constrain the TP profile of the ultra-hot Jupiter KELT-9b by fitting synthetic spectra to the observed Hα and Hβ lines and identify why self-consistent planetary TP models are unable to fit the observations. Methods. We constructed 126 one-dimensional TP profiles varying the lower and upper atmospheric temperatures, as well as the location and gradient of the temperature rise. For each TP profile, we computed the transmission spectra of the Hα and Hβ lines employing the Cloudy radiative transfer code, which self-consistently accounts for non-local thermodynamic equilibrium (NLTE) effects. Results. The TP profiles, leading to best fit the observations, are characterised by an upper atmospheric temperature of 10 000–11 000 K and by an inverted temperature profile at pressures higher than 10−4 bar. We find that the assumption of local thermodynamic equilibrium (LTE) leads one to overestimate the level population of excited hydrogen by several orders of magnitude and hence to significantly overestimate the strength of the Balmer lines. The chemical composition of the best fitting models indicate that the high upper atmospheric temperature is most likely driven by metal photoionisation and that FeII and FeIII have comparable abundances at pressures lower than 10−6 bar, possibly making the latter detectable. Conclusions. Modelling the atmospheres of ultra-hot Jupiters requires one to account for metal photoionisation. The high atmospheric mass-loss rate (>1011 g s−1), caused by the high temperature, may have consequences on the planetary atmospheric evolution. Other ultra-hot Jupiters orbiting early-type stars may be characterised by similarly high upper atmospheric temperatures and hence high mass-loss rates. This may have consequences on the basic properties of the observed planets orbiting hot stars.

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Section: Relevance Of Nlte Effectsmentioning

confidence: 99%

Section: Relevance Of Nlte Effectsmentioning

confidence: 99%

A data-driven approach to constraining the atmospheric temperature structure of the ultra-hot Jupiter KELT-9b

Fossati

Shulyak

Sreejith

et al. 2020

A&A

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“…HCN has been searched for in hot H 2 atmospheres with high-resolution spectroscopy, and an abundance of 10 −5 has been considered, placing a minimum limit on the HCN mixing ratio of log (HCN)=-6.5 in the atmosphere of the Hot Jupiter HD 209458b (Hawker et al 2018). Disequilibrium chemistry (vertical mixing) can enhance HCN abundances, dredgingup HCN to upper layers of the atmosphere and opening the possibility to detect it with future space-based facilities (Shulyak et al 2020). HCN abundances in N 2 -dominated atmospheres depend critically on the atmospheric C/O ratio, with significantly greater amounts of HCN generated photochemically when C/O ≥ 1 (Rimmer & Rugheimer 2019).…”

Section: Hcn In Other Planetary Atmospheresmentioning

confidence: 99%

Ground-based HCN submillimetre measurements in Titan's atmosphere: an intercomparison with Herschel observations

Rengel,

Shulyak,

Hartogh

et al. 2021

Preprint

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Aims. The aim of this study is to measure the vertical distribution of HCN on Titan's stratosphere using ground-based submillimetre observations acquired quasi-simultaneously with the Herschel ones. This allows us to perform a consistency check between space and ground-based observations and to build a reference mean HCN vertical profile in Titan's stratosphere. Methods. Using APEX and IRAM 30-m, we obtained the spectral emission of HCN (4-3) and (3-2) lines. Observations were reduced with GILDAS-CLASS. We applied a line-by-line radiative transfer code to calculate the synthetic spectra of HCN, and a retrieval algorithm based on optimal estimation to retrieve the temperature and HCN vertical distributions. We used the standard deviationbased metric to quantify the dispersion between the ground-based and Herschel HCN profiles and the mean one. Results. Our derived HCN abundance profiles are consistent with an increase from 40 ppb at ∼100 km to 4 ppm at ∼200 km, which is an altitude region where the HCN signatures are sensitive. We also demonstrate that the retrieved HCN distribution is sensitive to the data information and is restricted to Titan's stratosphere. The HCN obtained from APEX data is less accurate than the one from IRAM data because of the poorer data quality, and covers a narrower altitude range. Comparisons between our results and the values from Herschel show similar abundance distributions, with maximum differences of 2.5 ppm ranging between 100 and 300 km in the vertical range. These comparisons also allow us to inter-validate both data sets and indicate reliable and consistent measurements. The inferred abundances are also consistent with the vertical distribution in previous observational studies, with the profiles from ALMA, Cassini/CIRS, and SMA (the latest ones below ∼230 km). Our HCN profile is also comparable to photochemical models by Krasnopolsky (2014) and Vuitton et al. (2019) below 230 km and consistent with that of Loison et al. (2015) above 250 km. However, it appears to show large differences with respect to the estimates by Loison et al. (2015), Dobrijevic & Loison (2018), and Lora et al. (2018) below 170 km, and by Dobrijevic & Loison (2018) and Lora et al. ( 2018) above 400 km, although they are similar in shape. We conclude that these particular photochemical models need improvement.

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“…In Tsai et al (2017), VUL-CAN is validated by comparing the quench behavior with ARGO (Rimmer & Helling 2016) and Moses et al (2011). Since then, VULCAN has been continuously updated and applied to several studies such as Zilinskas et al (2020) who identify key molecules of hot super-Earths with nitrogendominated atmospheres, and Shulyak et al (2020) who explore the effects of XUV for different stellar types.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of Atmospheric Chemistry with VULCAN

Tsai,

Malik,

Kitzmann

et al. 2021

Preprint

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We present an update of the open-source photochemical kinetics code VULCAN (Tsai et al. (2017); https://github.com/exoclime/VULCAN) to include C-H-N-O-S networks and photochemistry. Additional new features are advection transport, condensation, various boundary conditions, and temperature-dependent UV cross-sections. First, we validate our photochemical model for hot Jupiter atmospheres by performing an intercomparison of HD 189733b models between Moses et al. (2011), Venot et al. (2012, and VULCAN, to diagnose possible sources of discrepancy. Second, we set up a model of Jupiter extending from the deep troposphere to upper stratosphere to verify the kinetics for low temperature. Our model reproduces hydrocarbons consistent with observations, and the condensation scheme successfully predicts the locations of water and ammonia ice clouds. We show that vertical advection can regulate the local ammonia distribution in the deep atmosphere. Third, we validate the model for oxidizing atmospheres by simulating Earth and find agreement with observations. Last, VULCAN is applied to four representative cases of extrasolar giant planets: WASP-33b, HD 189733b, GJ 436b, and 51 Eridani b. We look into the effects of the C/O ratio and chemistry of titanium/vanadium species for WASP-33b; we revisit HD 189733b for the effects of sulfur and carbon condensation; the effects of internal heating and vertical mixing (K zz ) are explored for GJ 436b; we test updated planetary properties for 51 Eridani b with S 8 condensates. We find sulfur can couple to carbon or nitrogen and impact other species such as hydrogen, methane, and ammonia. The observable features of the synthetic spectra and trends in the photochemical haze precursors are discussed for each case.

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

Cited by 22 publications

References 101 publications

A data-driven approach to constraining the atmospheric temperature structure of the ultra-hot Jupiter KELT-9b

A data-driven approach to constraining the atmospheric temperature structure of the ultra-hot Jupiter KELT-9b

Ground-based HCN submillimetre measurements in Titan's atmosphere: an intercomparison with Herschel observations

A Comparative Study of Atmospheric Chemistry with VULCAN

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