ABSTRACT New molecular line lists for lithium hydroxide (6Li16O1H and 7Li16O1H isotopologues) covering wavelengths λ > 1 $\mu$m (0–10 000 cm−1 range) are presented. Each line list contains around 300 million transitions between rotation–vibration energy levels with total angular momentum up to J = 95, applicable for temperatures up to T ≈ 3500 K. Line list calculations were based on a previously published, high-level ab initio potential energy surface and a newly computed dipole moment surface of the ground $\tilde{X}\, ^1\Sigma ^+$ electronic state. Lithium-containing molecules are important in a variety of stellar objects and there is potential for LiOH to be observed in the atmospheres of exoplanets. Transit spectra are simulated using the rocky super-Earth 55 Cancri e as an example with two different atmospheric scenarios including LiOH. This work provides the first, comprehensive line lists of LiOH to facilitate its future molecular detection. The OYT7 line lists along with the associated temperature- and pressure-dependent molecular opacities can be downloaded from the ExoMol database at www.exomol.com and the CDS astronomical database.

We would like to present the atmospheric characterisation of three large, gaseous planets: WASP-127b, WASP-79b and WASP-62b. We analysed spectroscopic data obtained with the G141 grism (1.088 - 1.68 um) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H$_2$O) = -2.71$^{+0.78}_{-1.05}$, and absorption compatible with an iron hydride abundance of log(FeH)=$-5.25^{+0.88}_{-1.10}$, with an extended cloudy atmosphere.We also detected water vapour in the atmospheres of WASP-79b and WASP-62b, with best-fit models indicating the presence of iron hydride, too.We used the Atmospheric Detectability Index (ADI) as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al 2018.While all the planets studied here are suitable targets for characterisation with upcoming facilities such as the James Webb Space Telescope (JWST) and Ariel, WASP-127b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration.

Great advances have been made over the last few decades in probing the atmospheres of extra-solar planets, enabling us to further constrain the conditions that exist on these worlds. When modelling these atmospheres however, the work done to date has assumed that the species present are in local thermodynamic equilibrium (LTE). However it is known, for instance on Earth, that non-LTE effects are present in planetary atmospheres and give rise to spectra that vary from the LTE case.Fast, high altitude jet streams in the atmospheres of hot Jupiters will produce shock regions where molecules may be found in non-LTE. Such effects are also likely in the upper atmospheres of planets barraged by solar flares, where the heavy stellar radiation drives the molecules to a state of non-LTE. This poster presents a preliminary exploration into non-LTE effects in exoplanet atmospheres, showing the differences that arise in some notable molecular spectra due to these effects. This is achieved with the atmospheric retrieval framework TauRex 3, using custom cross sections generated with the ExoCross software’s capability to approximate non-LTE spectra via splitting the rotational and vibrational temperatures. An initial evaluation of the detectability of these differences by current and next generation space telescopes is presented through simulation with the PandExo package, showing forward atmospheric models with non-LTE variations clearly visible in spectra. It can be seen that the differences in spectra are resolvable, notably the absence of ‘shoulders’ in the case of the non-LTE water transmission models.

The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and brown dwarfs. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the "data-provider" and "data-user" communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in databases, theoretical, or literature sources.

As next generation observation facilities become available for the characterisation of Exoplanet atmospheres, the capacity to move beyond the assumption of molecules existing in local thermodynamic equilibrium becomes more pressing. While atmospheric retrieval of Exoplanet atmospheres has operated under this assumption, it is known that many effects within planetary atmospheres drive molecules away from this equilibrium - into a state of non-local thermodynamic equilibrium, or non-LTE. Here we revisit the bi-temperature model for approximating non-LTE molecule populations which uses a two temperature parameterisation: distinct rotational and vibrational temperatures. Here the implementation of this model is used in the molecular cross section generation code Exocross (Yurchenko et al. 2018) to further explore the differences arising in forward modelled spectra due to molecules existing in non-LTE.Now we include an exploration of non-LTE in the the optical with the additional consideration of Titanium Oxide (TiO) - this diatomic exhibits bands of accentuated intensity when in non-LTE. This can be seen in the figure shown here - forward model examples for TiO in the atmosphere of WASP-76b with 3 transit observations simulated for JWST's NIRSpec instrument set to use its G140H grating. Here the divergence between spectra for the LTE and non-LTE cases can be seen to be particularly pronounced around 0.85 micron. In addition we show that the bi-temperature paramterisation is tractable for atmospheric retrieval. Here modifications were made to the publicly available atmospheric retrieval code TauREx 3 to include the additional temperature degree of freedom and non-LTE cross section data were generated using the Exocross code. This enables us to demonstrate the retrieval of both rotational and vibrational temperature parameters from JWST data simulated with under 10 transits.

One of the main objectives of the European Space Agency's Ariel telescope (launch 2029) is to understand the formation and evolution processes of a large sample of planets in our Galaxy. Important indicators of such processes in giant planets are the elemental compositions of their atmospheres. Here we investigate the capability of Ariel to constrain four key atmospheric markers: metallicity, C/O, S/O, and N/O, for three well-known, representative hot-Jupiter atmospheres observed with transit spectroscopy, i.e. HD 209458b, HD 189733b, and WASP-121b. We have performed retrieval simulations for these targets to verify how the planetary formation markers listed above would be recovered by Ariel when observed as part of the Ariel Tier 3 survey. We have considered eight simplified different atmospheric scenarios with a cloud-free isothermal atmosphere. Additionally, extra cases were tested to illustrate the effect of C/O and metallicity in recovering the N/O. From our retrieval results, we conclude that Ariel is able to recover the majority of planetary formation markers. The contributions from CO and CO2 are dominant for the C/O in the solar scenario. In a C-rich case, C2H2, HCN, and CH4 may provide additional spectral signatures that can be captured by Ariel. In our simulations, H2S is the main tracer for the S/O in hot-Jupiter atmospheres. In the super-solar metallicity cases and the cases with C/O > 1, the increased abundance of HCN is easily detectable and the main contributor to N/O, while other N-bearing species contribute little to the N/O in the investigated atmospheres.

Individual vibrational band spectroscopy presents an opportunity to examine exoplanet atmospheres in detail by distinguishing where the vibrational state populations of molecules differ from the current assumption of a Boltzmann distribution. Here, retrieving vibrational bands of OH in exoplanet atmospheres is explored using the hot Jupiter WASP-33b as an example. We simulate low-resolution spectroscopic data for observations with the JWST's NIRSpec instrument and use high resolution observational data obtained from the Subaru InfraRed Doppler instrument (IRD). Vibrational band-specific OH cross section sets are constructed and used in retrievals on the (simulated) low and (real) high resolution data. Low resolution observations are simulated for two WASP-33b emission scenarios: under the assumption of local thermal equilibrium (LTE) and a toy non-LTE model for vibrational excitation of selected bands. We show that mixing ratios for individual bands can be retrieved with sufficient precision to allow the vibrational population distributions of the forward models to be reconstructed. A simple fit for the Boltzmann distribution in the LTE case shows that the vibrational temperature is recoverable in this manner. For high resolution, cross-correlation applications, we apply the individual vibrational band analysis to an IRD spectrum of WASP-33b, applying an 'un-peeling' technique. Individual detection significances for the two strongest bands are shown to be in line with Boltzmann distributed vibrational state populations consistent with the effective temperature of the WASP-33b atmosphere reported previously. We show the viability of this approach for analysing the individual vibrational state populations behind observed and simulated spectra including reconstructing state population distributions.

ABSTRACT Here we present a study of non-local thermodynamic equilibrium (LTE) effects on the exoplanetary spectra of a collection of molecules that are key in the investigation of exoplanet atmospheres: water, methane, carbon monoxide, and titanium oxide. These molecules are chosen as examples of different spectral ranges (infrared and ultraviolet), molecular types (diatomics and polyatomics), and spectral types (electronic and rovibrational); the importance of different vibrational bands in forming distinct non-LTE spectral features is investigated. Most notably, such key spectral signatures for distinguishing between the LTE and non-LTE cases include: for CH4 the 3.15 $\mu$m band region; for H2O the 2.0 and 2.7 $\mu$m band regions; for TiO, a strong variation in intensity in the bands between 0.5 and 0.75 $\mu$m; and a sole CO signature between 5 and 6 $\mu$m. The analysis is based on the ExoMol cross-sections and takes advantage of the extensive vibrational assignment of these molecular line lists in the ExoMol data base. We examine LTE and non-LTE cross-sections under conditions consistent with those on WASP-12b and WASP-76b using the empirically motivated bi-temperature Treanor model.

We predict that cyanoacetylene (HC3N) is produced photochemically in the atmosphere of GJ 1132 b in abundances detectable by the James Webb Space Telescope (JWST), assuming that the atmosphere is hydrogen dominated and rich in molecular nitrogen (N2), methane (CH4), and hydrogen cyanide (HCN), as described by Swain et al. First, we construct line lists and cross sections for HC3N. Then we apply these cross sections and the model atmosphere of Swain et al. to a radiative transfer model in order to simulate the transmission spectrum of GJ 1132 b as it would be seen by JWST, accounting for the uncertainty in the retrieved abundances. We predict that cyanoacetylene features at various wavelengths, with a clear lone feature at 4.5 μm, observable by JWST after one transit. This feature persists within the 1σ uncertainty of the retrieved abundances of HCN and CH4. The signal is detectable for stratospheric temperatures ≲600 K and moderate stratospheric mixing (106 cm2 s−1 ≲ K zz ≲ 108 cm2 s−1). Our results also indicate that HC3N is an important source of opacity that future retrieval models should consider.

We present a study on the spatially scanned spectroscopic observations of the transit of GJ 1132 b, a warm (~500 K) Super-Earth (1.13 Re) that was obtained with the G141 grism (1.125 - 1.650 micron) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope. We used the publicly available Iraclis pipeline to extract the planetary transmission spectra from the five visits and produce a precise transmission spectrum. We analysed the spectrum using the TauREx3 atmospheric retrieval code with which we show that the measurements do not contain molecular signatures in the investigated wavelength range and are best-fit with a flat-line model. Our results suggest that the planet does not have a clear primordial, hydrogen-dominated atmosphere. Instead, GJ 1132 b could have a cloudy hydrogen-dominated envelope, a very enriched secondary atmosphere, be airless, or have a tenuous atmosphere that has not been detected. Due to the narrow wavelength coverage of WFC3, these scenarios cannot be distinguished yet but the James Webb Space Telescope may be capable of detecting atmospheric features, although several observations may be required to provide useful constraints

We present an atmospheric characterization study of two medium-sized planets bracketing the radius of Neptune: HD 106315c (R-P.=.4.98 +/- 0.23 R-circle plus) and HD 3167c (R-P = 2.740(-0.100)(+0.100) R-circle plus). We analyze spatially scanned spectroscopic observations obtained with the G141 grism (1.125-1.650 mu m) of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. We use the publicly available Iraclis pipeline and TauREx3 atmospheric retrieval code and detect water vapor in the atmosphere of both planets, with an abundance of log(10)[H2O] -2.1(-1.3)(+0.7) (similar to 5.68 sigma) and = log(10)[H2O] = -4.1(-0.9)(+0.9) (similar to 3.17s) for HD 106315c and HD 3167c, respectively. The transmission spectrum of HD 106315c also shows possible evidence of ammonia absorption (log(10)[NH3] = -4.3(-2.0)(+0.7), similar to 1.97 sigma, even if it is not significant), while carbon dioxide absorption features may be present in the atmosphere of HD 3167c in the similar to 1.1-1.6 mu m wavelength range (log(10)[CO2] = -2.4(-1.0)(+0.7), similar to 3.28 sigma). However, the CO2 detection appears significant, and it must be considered carefully and put into perspective. Indeed, CO2 presence is not explained by 1D equilibrium chemistry models, and it could be due to possible systematics. The additional contributions of clouds, CO, and CH4 are discussed. HD 106315c and HD 3167c will be interesting targets for upcoming telescopes such as the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.

We present the analysis of the hot-Jupiter KELT-7 b using transmission and emission spectroscopy from the Hubble Space Telescope, both taken with the Wide Field Camera 3. Our study uncovers a rich transmission spectrum that is consistent with a cloud-free atmosphere and suggests the presence of H 2 O and H − . In contrast, the extracted emission spectrum does not contain strong absorption features and, although it is not consistent with a simple blackbody, it can be explained by a varying temperature–pressure profile, collision induced absorption, and H − . KELT-7 b had also been studied with other space-based instruments and we explore the effects of introducing these additional data sets. Further observations with Hubble, or the next generation of space-based telescopes, are needed to allow for the optical opacity source in transmission to be confirmed and for molecular features to be disentangled in emission.

This paper presents the atmospheric characterization of three large, gaseous planets: WASP-127 b, WASP-79 b, and WASP-62 b. We analyzed spectroscopic data obtained with the G141 grism (1.088-1.68 mu m) of theWide Field Camera 3 on board the Hubble Space Telescope using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127 b, which is the least dense planet discovered so far and is located in the shortperiod Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H2O).=.-2.71(-1.05)(+0.78) and absorption compatible with an iron hydride abundance of log(FeH) = -5.25(-1.10)(+0.88), with an extended cloudy atmosphere. We also detected water vapor in the atmospheres of WASP-79 b and WASP-62 b, with best-fit models indicating the presence of iron hydride, too. We used the Atmospheric Detectability Index as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al. While all the planets studied here are suitable targets for characterization with upcoming facilities such as the James Webb Space Telescope and Ariel, WASP-127 b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration.

We analyze the transmission and emission spectra of the ultra-hot Jupiter WASP-76 b, observed with the G141 grism of the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3). We reduce and fit the raw data for each observation using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauREx 3. Previous studies of the WFC3 transmission spectra of WASP-76 b found hints of titanium oxide (TiO) and vanadium oxide (VO) or non-gray clouds. Accounting for a fainter stellar companion to WASP-76, we reanalyze this data and show that removing the effects of this background star changes the slope of the spectrum, resulting in these visible absorbers no longer being detected, eliminating the need for a non-gray cloud model to adequately fit the data but maintaining the strong water feature previously seen. However, our analysis of the emission spectrum suggests the presence of TiO and an atmospheric thermal inversion, along with a significant amount of water. Given the brightness of the host star and the size of the atmospheric features, WASP-76 b is an excellent target for further characterization with HST, or with future facilities, to better understand the nature of its atmosphere, to confirm the presence of TiO and to search for other optical absorbers.