Ariel will require precise knowledge of the transit timings for all of its targets. However, the precision we have for each target will degrade significantly over the 8 years until launch, in some cases to the point where the error exceeds the duration of the transit itself. The knowledge of these transits would then be deemed “lost”. To counteract this, and in effect “reset the clock”, we aim to use the Telescope Live network of robotic telescopes to observe such targets. With 1000 targets and an average orbital period of the order of days, the size and usage of the network required needs to be quantified. Here we present results from simulations of these observations for a variety of telescope networks of varying sizes, the number of targets that can be successfully constrained, and the amount of observing time required to do so. From these results we can conclude that a ground-based telescope network containing as few as 2 telescopes of 0.6m aperture can constrain over 60% of the targets with transit depths observable from the ground. A fraction of these exoplanets are difficult to observe with ground-based telescopes as they either have transit depths too shallow to detect due to atmospheric distortion and/or their transit durations are comparable to the length of a night, reducing the probability of observable transits occurring. Such targets would benefit from supplementary observations from space-based observatories, as these do not suffer from either atmospheric distortion or limits on observing time due to Earth’s diurnal cycle.

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution.

The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project makes the best use of all available resources, i.e., observations from ground telescopes, midtime values from the literature, and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85% of the currently known Ariel candidate targets. This work includes the results of ∼1600 observations obtained up to 2020 December 31 from the ExoClock network. These data in combination with ∼2350 midtime values collected from the literature are used to update the ephemerides of 180 planets. The analysis shows that 40% of the updated ephemerides will have an impact on future scheduling as either they have a significantly improved precision or they have revealed biases in the old ephemerides. With the new observations, the observing coverage and rate for half of the planets in the sample has been doubled or more. Finally, from a population perspective, we identify that the differences in the 2028 predictions between the old and the new ephemerides have an STD that is double what is expected from Gaussian uncertainties. These findings have implications for planning future observations, where we will need to account for drifts potentially greater than the prediction uncertainties. The updated ephemerides are open and accessible to the wider exoplanet community both from our Open Science Framework repository and our website.

Here we present a publicly available database of opacities for molecules of astrophysical interest named ExoMolOP that has been compiled for over 80 species, and is based on the latest line list data from the ExoMol, HITEMP, and MoLLIST databases. These data are generally suitable for characterising high-temperature exoplanet or cool stellar and substellar atmospheres, and have been computed at a variety of pressures and temperatures, with a few molecules included at room temperature only from the HITRAN database. The data are formatted in different ways for four different exoplanet atmosphere retrieval codes; ARCiS, TauREx, NEMESIS, and petitRADTRANS, and include both cross sections (atR=λ/Δλ= 15000) andk-tables (atR=λ/Δλ= 1000) for the 0.3–50μm wavelength region. Opacity files can be downloaded and used directly for these codes. Atomic data for alkali metals Na and K are also included, using data from the NIST database and the latest line shapes for the resonance lines. Broadening parameters have been taken from the literature where available, or have been estimated from the parameters of a known molecule with similar molecular properties where no broadening data are available.

The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planets’ ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observed by Ariel. The project has been developed in a manner to make the best use of all available resources: observations reported in the literature, observations from space instruments and, mainly, observations from ground-based telescopes, including both professional and amateur observatories. To facilitate inexperienced observers and at the same time achieve homogeneity in the results, we created data collection and validation protocols, educational material and easy to use interfaces, open to everyone. ExoClock was launched in September 2019 and now counts over 140 participants from more than 15 countries around the world. In this release, we report the results of observations obtained until the 15h of April 2020 for 120 Ariel candidate targets. In total, 632 observations were used to either verify or update the ephemerides of 84 planets. Additionally, we developed the Exoplanet Characterisation Catalogue (ECC), a catalogue built in a consistent way to assist the ephemeris refinement process. So far, the collaborative open framework of the ExoClock project has proven to be highly efficient in coordinating scientific efforts involving diverse audiences. Therefore, we believe that it is a paradigm that can be applied in the future for other research purposes, too.

We report photometric follow-up observations of thirteen exoplanets (HATS-1 b, HATS2 b, HATS-3 b, HAT-P-18 b, HAT-P-27 b, HAT-P-30 b, HAT-P-55 b, KELT-4A b, WASP-25 b, WASP-42 b, WASP-57 b, WASP-61 b and WASP-123 b), as part of the Original Research By Young Twinkle Students (ORBYTS) programme. All these planets are potentially viable targets for atmospheric characterisation and our data, which were taken using the LCOGT network of ground-based telescopes, will be combined with observations from other users of ExoClock to ensure that the transit times of these planets continue to be well-known, far into the future.

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/SiH2/28Si-1H2/CATS.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check SiH2_28Si1H2_CATS.md for detailed information.Definitions file 28Si-1H2__CATS.def[8.4 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/SiH2/28Si-1H2/CATS/CATS: partition function SiH2 line list CATS obtained using a refined PES and ab initio DMS, computed with TROVE28Si-1H2__CATS.pf[48.83 KB]A CATS partition function, (28Si)(1H)2. References:1. Clark, V. H. J., Owens, A., Tennyson, J., Yurchenko, S. N., "The high-temperature rotation-vibration spectrum and rotational clustering of silylene (SiH2)", Journal of Quantitative Spectroscopy and Radiative Transfer 246, 106929 (2021). [https://doi.org/10.1016/j.jqsrt.2020.106929][21ClOwTe.SiH2]CATS: line list SiH2 line list CATS obtained using a refined PES and ab initio DMS, computed with TROVE28Si-1H2__CATS.states.bz2[6.9 MB]A CATS .states file. (28Si)(1H)2 hot line list. 28Si-1H2__CATS__00000-01000.trans.bz2[80.78 MB]CATS hot line list transitions, (28Si)(1H)2: 0-1000 cm-1. 28Si-1H2__CATS__01000-02000.trans.bz2[105.67 MB]CATS hot line list transitions, (28Si)(1H)2: 1000-2000 cm-1. 28Si-1H2__CATS__02000-03000.trans.bz2[134.01 MB]CATS hot line list transitions, (28Si)(1H)2: 2000-3000 cm-1. 28Si-1H2__CATS__03000-04000.trans.bz2[167.82 MB]CATS hot line list transitions, (28Si)(1H)2: 3000-4000 cm-1. 28Si-1H2__CATS__04000-05000.trans.bz2[205.19 MB]CATS hot line list transitions, (28Si)(1H)2: 4000-5000 cm-1. 28Si-1H2__CATS__05000-06000.trans.bz2[249.32 MB]CATS hot line list transitions, (28Si)(1H)2: 5000-6000 cm-1. 28Si-1H2__CATS__06000-07000.trans.bz2[298.96 MB]CATS hot line list transitions, (28Si)(1H)2: 6000-7000 cm-1. 28Si-1H2__CATS__07000-08000.trans.bz2[354.93 MB]CATS hot line list transitions, (28Si)(1H)2: 7000-8000 cm-1. 28Si-1H2__CATS__08000-09000.trans.bz2[415.19 MB]CATS hot line list transitions, (28Si)(1H)2: 8000-9000 cm-1. 28Si-1H2__CATS__09000-10000.trans.bz2[476.85 MB]CATS hot line list transitions, (28Si)(1H)2: 9000-10000 cm-1. References:1. Clark, V. H. J., Owens, A., Tennyson, J., Yurchenko, S. N., "The high-temperature rotation-vibration spectrum and rotational clustering of silylene (SiH2)", Journal of Quantitative Spectroscopy and Radiative Transfer 246, 106929 (2021). [https://doi.org/10.1016/j.jqsrt.2020.106929][21ClOwTe.SiH2]CATS: opacity SiH2 line list CATS obtained using a refined PES and ab initio DMS, computed with TROVE28Si-1H2__CATS.R1000_0.3-50mu.ktable.ARCiS.fits.gz[339.68 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): CATS (28Si)(1H)2 line list. 28Si-1H2__CATS.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: CATS (28Si)(1H)2 line list. 28Si-1H2__CATS.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: CATS (28Si)(1H)2 line list. 28Si-1H2__CATS.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx k-tables at R= 15000 (0.3-50mu) in HDF5 format: CATS (28Si)(1H)2 line list. References:1. Clark, V. H. J., Owens, A., Tennyson, J., Yurchenko, S. N., "The high-temperature rotation-vibration spectrum and rotational clustering of silylene (SiH2)", Journal of Quantitative Spectroscopy and Radiative Transfer 246, 106929 (2021). [https://doi.org/10.1016/j.jqsrt.2020.106929][21ClOwTe.SiH2]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/NaOH/23Na-16O-1H/OYT5.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check NaOH_23Na16O1H_OYT5.md for detailed information.Definitions file 23Na-16O-1H__OYT5.def[7.4 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/NaOH/23Na-16O-1H/OYT5/OYT5: line list NB: These data are not included in the current version on Zenodo because the data are over Zenodo upload cap, 50GBData can be accessed via: https://exomol.com/data/molecules/NaOH/23Na-16O-1H/OYT5References:1. Owens, A., Tennyson. J, Yurchenko, S.N., "ExoMol line lists - XLI. High-temperature molecular line lists for the alkali metal hydroxides KOH and NaOH", Monthly Notices of the Royal Astronomical Society 502(1), 1128-1135 (2021). [https://doi.org/10.1093/mnras/staa4041]OYT5: partition function OYT5 hot ro-vibrational line list for NaOH.23Na-16O-1H__OYT5.pf[97.66 KB]The Partition Function file from the OYT5 line list for NaOH. References:1. Owens, A., Tennyson. J, Yurchenko, S.N., "ExoMol line lists - XLI. High-temperature molecular line lists for the alkali metal hydroxides KOH and NaOH", Monthly Notices of the Royal Astronomical Society 502(1), 1128-1135 (2021). [https://doi.org/10.1093/mnras/staa4041]OYT5: opacity OYT5 hot ro-vibrational line list for NaOH.23Na-16O-1H__OYT5.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: OYT5 (23Na)(16O)(1H) line list. 23Na-16O-1H__OYT5.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx cross sections at R= 15000 (0.3-50mu) in HDF5 format: OYT5 (23Na)(16O)(1H) line list. 23Na-16O-1H__OYT5.R1000_0.3-50mu.ktable.ARCiS.fits.gz[306.06 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): OYT5 (23Na)(16O)(1H) line list. 23Na-16O-1H__OYT5.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: OYT5 (23Na)(16O)(1H) line list. References:1. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]2. Owens, A., Tennyson. J, Yurchenko, S.N., "ExoMol line lists - XLI. High-temperature molecular line lists for the alkali metal hydroxides KOH and NaOH", Monthly Notices of the Royal Astronomical Society 502(1), 1128-1135 (2021). [https://doi.org/10.1093/mnras/staa4041]

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/NH3/14N-1H3/CoYuTe.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check NH3_14N1H3_CoYuTe.md for detailed information.Definitions file 14N-1H3__CoYuTe.def[16.5 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/NH3/14N-1H3/CoYuTe/CoYuTe: line list NB: These data are not included in the current version on Zenodo because the data are over Zenodo upload cap, 50GBData can be accessed via: https://exomol.com/data/molecules/NH3/14N-1H3/CoYuTeReferences:1. Al Derzi, A. R., Furtenbacher, T., Tennyson, J., Yurchenko, S. N., Császár, A. G., "MARVEL analysis of the measured high-resolution spectra of 14NH3", unknown journal 161, 117-130 (2015). [https://doi.org/10.1016/j.jqsrt.2015.03.034][15AlFuTe.NH3]2. Coles, P. A., Yurchenko, S. N., Tennyson, J., "ExoMol molecular line lists – XXXV. A rotation-vibration line list for hot ammonia", Monthly Notices of the Royal Astronomical Society 490, 4638-4647 (2019). [https://doi.org/10.1093/mnras/stz2778][19CoYuTe.NH3]CoYuTe: partition function Hot Temperature line list for (14N)(1H)3, 0-20000 cm-1.14N-1H3__CoYuTe.pf[48.83 KB]Partition function (T=0-2000K) of the CoYuTe line list for (14N)(1H)3 References:1. Coles, P. A., Yurchenko, S. N., Tennyson, J., "ExoMol molecular line lists – XXXV. A rotation-vibration line list for hot ammonia", Monthly Notices of the Royal Astronomical Society 490, 4638-4647 (2019). [https://doi.org/10.1093/mnras/stz2778][19CoYuTe.NH3]CoYuTe: super-line NB: These data are not included in current version on ZenodoData can be accessed via: https://exomol.com/data/molecules/NH3/14N-1H3/CoYuTeCoYuTe: ExoCross input file NB: These data are not included in current version on ZenodoData can be accessed via: https://exomol.com/data/molecules/NH3/14N-1H3/CoYuTeCoYuTe: opacity Hot Temperature line list for (14N)(1H)3, 0-20000 cm-1.14N-1H3__CoYuTe.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: CoYuTe (14N)(1H)3 line list. 14N-1H3__CoYuTe.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx cross sections at R= 15000 (0.3-50mu) in HDF5 format: CoYuTe (14N)(1H)3 line list. 14N-1H3__CoYuTe.R1000_0.3-50mu.ktable.ARCiS.fits.gz[397.89 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): CoYuTe (14N)(1H)3 line list. 14N-1H3__CoYuTe.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: CoYuTe (14N)(1H)3 line list. References:1. Coles, P. A., Yurchenko, S. N., Tennyson, J., "ExoMol molecular line lists – XXXV. A rotation-vibration line list for hot ammonia", Monthly Notices of the Royal Astronomical Society 490, 4638-4647 (2019). [https://doi.org/10.1093/mnras/stz2778][19CoYuTe.NH3]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]CoYuTe: other States files NB: These data are not included in current version on ZenodoData can be accessed via: https://exomol.com/data/molecules/NH3/14N-1H3/CoYuTe

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/HeH_p/4He-1H_p/ADJSAAM.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check HeH_p_4He1H+_ADJSAAM.md for detailed information.Definitions file 4He-1H_p__ADJSAAM.def[4.95 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/HeH_p/4He-1H_p/ADJSAAM/ADJSAAM: line list Ab initio line list for isotopologues of HD, HD+ and HeH+ by Amaral et al (2019)4He-1H_p__ADJSAAM.trans.bz2[15.86 KB]Transition file from the ADJSAAM line list for (4He)(1H)+. 4He-1H_p__ADJSAAM.states.bz2[1.92 KB]Energy (States) file from the ADJSAAM line list for (4He)(1H)+. References:1. Amaral, P. H. R., Diniz, L.G., Jones, K.A., Stanke, M., Alijah, A., Adamowicz, L., Mohallem, J.R., "Benchmark Rovibrational Linelists and Einstein A-coefficients for the Primordial Molecules and Isotopologues", The Astrophysical Journal 878, 95 (2019). [https://doi.org/10.3847/1538-4357/ab1f65]ADJSAAM: partition function Ab initio line list for isotopologues of HD, HD+ and HeH+ by Amaral et al (2019)4He-1H_p__ADJSAAM.pf[195.31 KB]Partition function file from the ADJSAAM line list for (4He)(1H)+. References:1. Amaral, P. H. R., Diniz, L.G., Jones, K.A., Stanke, M., Alijah, A., Adamowicz, L., Mohallem, J.R., "Benchmark Rovibrational Linelists and Einstein A-coefficients for the Primordial Molecules and Isotopologues", The Astrophysical Journal 878, 95 (2019). [https://doi.org/10.3847/1538-4357/ab1f65]ADJSAAM: opacity Ab initio line list for isotopologues of HD, HD+ and HeH+ by Amaral et al (2019)4He-1H_p__ADJSAAM.R1000_0.3-50mu.ktable.ARCiS.fits.gz[351.92 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): ADJSAAM (4He)(1H)+ line list. 4He-1H_p__ADJSAAM.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: ADJSAAM (4He)(1H)+ line list. 4He-1H_p__ADJSAAM.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: ADJSAAM (4He)(1H)+ line list. 4He-1H_p__ADJSAAM.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx k-tables at R= 15000 (0.3-50mu) in HDF5 format: ADJSAAM (4He)(1H)+ line list. References:1. Amaral, P. H. R., Diniz, L.G., Jones, K.A., Stanke, M., Alijah, A., Adamowicz, L., Mohallem, J.R., "Benchmark Rovibrational Linelists and Einstein A-coefficients for the Primordial Molecules and Isotopologues", The Astrophysical Journal 878, 95 (2019). [https://doi.org/10.3847/1538-4357/ab1f65]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]

Over the last several years, spectroscopic observations of transiting exoplanets have begun to uncover information about their atmospheres, including atmospheric composition and indications of the presence of clouds and hazes. Spectral retrieval is the leading technique for interpretation of transmission spectra and is employed by several teams using a variety of forward models and parameter estimation algorithms. However, different model suites have mostly been used in isolation and so it is unknown whether the results from each are comparable. As we approach the launch of the James Webb Space Telescope we anticipate advances in wavelength coverage, precision, and resolution of transit spectroscopic data, so it is important that the tools that will be used to interpret these information rich spectra are validated. To this end, we present an inter-model comparison of three retrieval suites: TauREx, NEMESIS and CHIMERA. We demonstrate that the forward model spectra are in good agreement (residual deviations on the order of 20 - 40 ppm), and discuss the results of cross retrievals between the three tools. Generally, the constraints from the cross retrievals are consistent with each other and with input values to within 1 sigma However, for high precision scenarios with error envelopes of order 30 ppm, subtle differences in the simulated spectra result in discrepancies between the different retrieval suites, and inaccuracies in retrieved values of several sigma. This can be considered analogous to substantial systematic/astrophysical noise in a real observation, or errors/omissions in a forward model such as molecular linelist incompleteness or missing absorbers.

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution.

Transmission spectroscopy provides us with information on the atmospheric properties at the limb, which is often intuitively assumed to be a narrow annulus around the planet. Consequently, studies have focused on the effect of atmospheric horizontal heterogeneities along the limb. Here we demonstrate that the region probed in transmission – the limb – actually extends significantly towards the day and night sides of the planet. We show that the strong day–night thermal and compositional gradients expected on synchronous exoplanets create sufficient heterogeneities across the limb that result in important systematic effects on the spectrum and bias its interpretation. To quantify these effects, we developed a 3D radiative-transfer model able to generate transmission spectra of atmospheres based on 3D atmospheric structures. We first apply this tool to a simulation of the atmosphere of GJ 1214 b to produce synthetic JWST observations and show that producing a spectrum using only atmospheric columns at the terminator results in errors greater than expected noise. This demonstrates the necessity for a real 3D approach to model data for such precise observatories. Secondly, we investigate how day–night temperature gradients cause a systematic bias in retrieval analysis performed with 1D forward models. For that purpose we synthesise a large set of forward spectra for prototypical HD 209458 b- and GJ 1214 b-type planets varying the temperatures of the day and night sides as well as the width of the transition region. We then perform typical retrieval analyses and compare the retrieved parameters to the ground truth of the input model. This study reveals systematic biases on the retrieved temperature (found to be higher than the terminator temperature) and abundances. This is due to the fact that the hotter dayside is more extended vertically and screens the nightside – a result of the non-linear properties of atmospheric transmission. These biases will be difficult to detect as the 1D profiles used in the retrieval procedure are found to provide an excellent match to the observed spectra based on standard fitting criteria. This must be kept in mind when interpreting current and future data.

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/cis-P2H2/cis-31P2-1H2/OY-Cis.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check cis-P2H2_cis-31P21H2_OY-Cis.md for detailed information.Definitions file cis-31P2-1H2__OY-Cis.def[8.25 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/cis-P2H2/cis-31P2-1H2/OY-Cis/OY-Cis: line list NB: These data are not included in the current version on Zenodo because the data are over Zenodo upload cap, 50GBData can be accessed via: https://exomol.com/data/molecules/cis-P2H2/cis-31P2-1H2/OY-CisReferences:1. Owens, A., Yurchenko, S. N., "Theoretical rotation-vibration spectroscopy of cis- and trans-diphosphene (P2H2) and the deuterated species P2HD", Journal of Chemical Physics 150, 194308/1-9 (2019). [https://doi.org/10.1063/1.5092767][19OwYuxx.P2H2]OY-Cis: partition function OY-Cis ro-vibrational line list for cis-P2H2cis-31P2-1H2__OY-Cis.pf[24.41 KB]Partition function produced using the Cis-(31P)2(1H)2 line list. References:1. Owens, A., Yurchenko, S. N., "Theoretical rotation-vibration spectroscopy of cis- and trans-diphosphene (P2H2) and the deuterated species P2HD", Journal of Chemical Physics 150, 194308/1-9 (2019). [https://doi.org/10.1063/1.5092767][19OwYuxx.P2H2]OY-Cis: opacity OY-Cis ro-vibrational line list for cis-P2H2cis-31P2-1H2__OY-Cis.R1000_0.3-50mu.ktable.ARCiS.fits.gz[295.65 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): OY-Cis (31P)2(1H)2 line list. cis-31P2-1H2__OY-Cis.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: OY-Cis (31P)2(1H)2 line list. cis-31P2-1H2__OY-Cis.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx k-tables at R= 15000 (0.3-50mu) in HDF5 format: OY-Cis (31P)2(1H)2 line list. cis-31P2-1H2__OY-Cis.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: OY-Cis (31P)2(1H)2 line list. References:1. Owens, A., Yurchenko, S. N., "Theoretical rotation-vibration spectroscopy of cis- and trans-diphosphene (P2H2) and the deuterated species P2HD", Journal of Chemical Physics 150, 194308/1-9 (2019). [https://doi.org/10.1063/1.5092767][19OwYuxx.P2H2]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]

We present here the analysis of 30 gaseous extrasolar planets, with temperatures between 600 and 2400 K and radii between 0.35 and 1.9 R Jup . The quality of the HST /WFC3 spatially scanned data combined with our specialized analysis tools allow us to study the largest and most self-consistent sample of exoplanetary transmission spectra to date and examine the collective behavior of warm and hot gaseous planets rather than isolated case studies. We define a new metric, the Atmospheric Detectability Index (ADI) to evaluate the statistical significance of an atmospheric detection and find statistically significant atmospheres in around 16 planets out of the 30 analyzed. For most of the Jupiters in our sample, we find the detectability of their atmospheres to be dependent on the planetary radius but not on the planetary mass. This indicates that planetary gravity plays a secondary role in the state of gaseous planetary atmospheres. We detect the presence of water vapour in all of the statistically detectable atmospheres, and we cannot rule out its presence in the atmospheres of the others. In addition, TiO and/or VO signatures are detected with 4 σ confidence in WASP-76 b, and they are most likely present in WASP-121 b. We find no correlation between expected signal-to-noise and atmospheric detectability for most targets. This has important implications for future large-scale surveys.

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/CH4/12C-1H4/YT34to10.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check CH4_12C1H4_YT34to10.md for detailed information.Definitions file 12C-1H4__YT34to10.def[21.85 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/CH4/12C-1H4/YT34to10/YT34to10: line list NB: These data are not included in the current version on Zenodo because the data are over Zenodo upload cap, 50GBData can be accessed via: https://exomol.com/data/molecules/CH4/12C-1H4/YT34to10References:1. Yurchenko, S. N., Tennyson, J., "ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K", Monthly Notices of the Royal Astronomical Society 440, 1649-1661 (2014). [http://http://dx.doi.org/10.1093/mnras/stu326][14YuTexx.CH4]2. Yurchenko, S. N., Amundsen, D. S., Tennyson, J., Waldmann, I. P., "A hybrid line list for CH4 and hot methane continuum", Astronomy and Astrophysics 605, A95/1-9 (2017). [https://doi.org/10.1051/0004-6361/201731026][17YuAmTe.CH4]YT34to10: partition function Calculated line list and energy levels for (12C)(1H)412C-1H4__YT34to10.pf[25.39 KB]Partition function of (12C)(1H)4 in 3 K intervals to 2000 K References:1. Yurchenko, S. N., Tennyson, J., "ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K", Monthly Notices of the Royal Astronomical Society 440, 1649-1661 (2014). [http://http://dx.doi.org/10.1093/mnras/stu326][14YuTexx.CH4]2. Yurchenko, S. N., Amundsen, D. S., Tennyson, J., Waldmann, I. P., "A hybrid line list for CH4 and hot methane continuum", Astronomy and Astrophysics 605, A95/1-9 (2017). [https://doi.org/10.1051/0004-6361/201731026][17YuAmTe.CH4]YT34to10: opacity Calculated line list and energy levels for (12C)(1H)412C-1H4__YT34to10.R1000_0.3-50mu.ktable.ARCiS.fits.gz[353.53 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): YT34to10 (12C)(1H)4 line list. 12C-1H4__YT34to10.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: YT34to10 (12C)(1H)4 line list. 12C-1H4__YT34to10.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: YT34to10 (12C)(1H)4 line list. 12C-1H4__YT34to10.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx k-tables at R= 15000 (0.3-50mu) in HDF5 format: YT34to10 (12C)(1H)4 line list. References:1. Yurchenko, S. N., Amundsen, D. S., Tennyson, J., Waldmann, I. P., "A hybrid line list for CH4 and hot methane continuum", Astronomy and Astrophysics 605, A95/1-9 (2017). [https://doi.org/10.1051/0004-6361/201731026][17YuAmTe.CH4]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]

The dataset is an archive of ExoMol page, https://exomol.com/data/molecules/CH3Cl/12C-1H3-35Cl/OYT.Please check the reference details according to the following description or directly from the website.NB: The html description skips data which are not included in the current version for the purpose of simplicity. Please check CH3Cl_12C1H335Cl_OYT.md for detailed information.Definitions file 12C-1H3-35Cl__OYT.def[9.14 KB]References:1. Tennyson, J., Yurchenko, S. N., Al-Refaie, A. F., Clark, V. H. J., Chubb, K. L., Conway, E. K., Dewan, A., Gorman, M. N., Hill, C., Lynas-Gray, A. E., Mellor, T., McKemmish, L. K., Owens, A., Polyansky, O. L., Semenov, M., Somogyi, W., Tinetti, G., Upadhyay, A., Waldmann, I., Wang, Y., Wright, S., Yurchenko, O. P., "The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres", J. Quant. Spectrosc. Rad. Transf., 255, 107228 (2020). [https://doi.org/10.1016/j.jqsrt.2020.107228] Spectroscopic Model https://exomol.com/models/CH3Cl/12C-1H3-35Cl/OYT/OYT: line list NB: These data are not included in the current version on Zenodo because the data are over Zenodo upload cap, 50GBData can be accessed via: https://exomol.com/data/molecules/CH3Cl/12C-1H3-35Cl/OYTReferences:1. Owens, A., Yachmenev, A., Thiel, W., Fateev, A., Tennyson, J., Yurchenko, S. N., "ExoMol line lists – XXIX. The rotation-vibration spectrum of methyl chloride up to 1200 K", Monthly Notices of the Royal Astronomical Society 479, 3002-3010 (2018). [https://doi.org/10.1093/mnras/sty1542][18OwYaTh.CH3Cl]OYT: partition function The OYT calculated high-temperature line list for CH3Cl12C-1H3-35Cl__OYT.pf[50.78 KB]OYT (12C)(1H)3(35Cl) partition function file References:1. Owens, A., Yachmenev, A., Thiel, W., Fateev, A., Tennyson, J., Yurchenko, S. N., "ExoMol line lists – XXIX. The rotation-vibration spectrum of methyl chloride up to 1200 K", Monthly Notices of the Royal Astronomical Society 479, 3002-3010 (2018). [https://doi.org/10.1093/mnras/sty1542][18OwYaTh.CH3Cl]OYT: super-line NB: These data are not included in current version on ZenodoData can be accessed via: https://exomol.com/data/molecules/CH3Cl/12C-1H3-35Cl/OYTOYT: opacity The OYT calculated high-temperature line list for CH3Cl12C-1H3-35Cl__OYT.R1000_0.3-50mu.ktable.ARCiS.fits.gz[298.77 MB]ARCiS k-tables at R= 1000 (0.3-50mu) in fits format (gzipped): OYT (12C)(1H)3(35Cl) line list. 12C-1H3-35Cl__OYT.R1000_0.3-50mu.ktable.petitRADTRANS.h5[370.98 MB]petitRADTRANS k-tables at R= 1000 (0.3-50mu) in HDF5 format: OYT (12C)(1H)3(35Cl) line list. 12C-1H3-35Cl__OYT.R1000_0.3-50mu.ktable.NEMESIS.kta[232.01 MB]NEMESIS k-tables at R= 1000 (0.3-50mu) in NEMESIS-kta format: OYT (12C)(1H)3(35Cl) line list. 12C-1H3-35Cl__OYT.R15000_0.3-50mu.xsec.TauREx.h5[348.39 MB]TauREx k-tables at R= 15000 (0.3-50mu) in HDF5 format: OYT (12C)(1H)3(35Cl) line list. References:1. Owens, A., Yachmenev, A., Thiel, W., Fateev, A., Tennyson, J., Yurchenko, S. N., "ExoMol line lists – XXIX. The rotation-vibration spectrum of methyl chloride up to 1200 K", Monthly Notices of the Royal Astronomical Society 479, 3002-3010 (2018). [https://doi.org/10.1093/mnras/sty1542][18OwYaTh.CH3Cl]2. Chubb, K. L., Rocchetto, M., Yurchenko, S. N., Min, M., Waldmann, I., Barstow, J. K., Molliere, P., Al-Refaie, A. F, Phillips, M. W., Tennyson, J., "The ExoMolOP database: Cross sections and k-tables for molecules of interest in high-temperature exoplanet atmospheres", Astronomy and Astrophysics 646, A21 (2020). [http://dx.doi.org/10.1051/0004-6361/202038350][20ChRoYu.]