Abstract
Spectral retrieval has long been a powerful tool for interpreting planetary remote sensing observations. Flexible, parameterised, agnostic models are coupled with inversion algorithms in order to infer atmospheric properties directly from observations, with minimal reliance on physical assumptions. This approach, originally developed for application to Earth satellite data and subsequently observations of other Solar System planets, has been recently and successfully applied to transit, eclipse and phase curve spectra of transiting exoplanets. In this review, we present the current state-of-the-art in terms of our ability to accurately retrieve information about atmospheric chemistry, temperature, clouds and spatial variability; we discuss the limitations of this, both in the available data and modelling strategies used; and we recommend approaches for future improvement.
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References
A.S. Ackerman, M.S. Marley, Precipitating condensation clouds in substellar atmospheres. Astrophys. J. 556, 872–884 (2001). https://doi.org/10.1086/321540
D.S. Amundsen, N.J. Mayne, I. Baraffe, J. Manners, P. Tremblin, B. Drummond, C. Smith, D.M. Acreman, D. Homeier, The UK Met Office global circulation model with a sophisticated radiation scheme applied to the hot Jupiter HD 209458b. Astron. Astrophys. 595, 36 (2016). https://doi.org/10.1051/0004-6361/201629183
J. Arcangeli, J.-M. Désert, V. Parmentier, K.B. Stevenson, M.R. Line, L. Kreidberg, J.J. Fortney, A.P. Showman, Climate of an ultra hot Jupiter. Spectroscopic phase curve of WASP-18b with HST/WFC3 Astron. Astrophys. 625, 136 (2019). https://doi.org/10.1051/0004-6361/201834891
T. Barman, Identification of absorption features in an extrasolar planet atmosphere. Astrophys. J. 661(2), 191–194 (2007). https://doi.org/10.1086/518736
J.K. Barstow, P.G.J. Irwin, Habitable worlds with JWST: transit spectroscopy of the TRAPPIST-1 system? Mon. Not. R. Astron. Soc. 461, 92–96 (2016). https://doi.org/10.1093/mnrasl/slw109
J.K. Barstow, S. Aigrain, P.G.J. Irwin, T. Hackler, L.N. Fletcher, J.M. Lee, N.P. Gibson, Clouds on the hot Jupiter HD189733b: constraints from the reflection spectrum. Astrophys. J. 786, 154 (2014). https://doi.org/10.1088/0004-637X/786/2/154
J.K. Barstow, S. Aigrain, P.G.J. Irwin, S. Kendrew, L.N. Fletcher, Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching. Mon. Not. R. Astron. Soc. 448(3), 2546–2561 (2015). https://doi.org/10.1093/mnras/stv186
J.K. Barstow, S. Aigrain, P.G.J. Irwin, D.K. Sing, A consistent retrieval analysis of 10 hot Jupiters observed in transmission. Astrophys. J. 834, 50 (2017). https://doi.org/10.3847/1538-4357/834/1/50
N. Batalha, J. Bean, K. Stevenson, M. Alam, N. Batalha, B. Benneke, Z. Berta-Thompson, J. Blecic, G. Bruno, A. Carter, J. Chapman, I. Crossfield, N. Crouzet, L. Decin, B. Demory, J. Desert, D. Dragomir, T. Evans, J. Fortney, J. Fraine, P. Gao, A. Garcia Munoz, N. Gibson, J. Goyal, J. Harrington, K. Heng, R. Hu, E. Kempton, S. Kendrew, B. Kilpatrick, H. Knutson, L. Kreidberg, J. Krick, P. Lagage, M. Lendl, M. Line, M. Lopez-Morales, T. Louden, N. Madhusudhan, A. Mandell, M. Mansfield, E. May, G. Morello, C. Morley, J. Moses, N. Nikolov, V. Parmentier, S. Redfield, J. Roberts, E. Schlawin, A. Showman, D. Sing, J. Spake, M. Swain, K. Todorov, A. Tsiaras, O. Venot, W. Waalkes, H. Wakeford, P. Wheatley, R. Zellem, The transiting exoplanet community early release science program, JWST Proposal ID 1366. Cycle 0 Early Release Science, 2017
B. Benneke, S. Seager, Atmospheric retrieval for super-earths: uniquely constraining the atmospheric composition with transmission spectroscopy. Astrophys. J. 753(2), 100 (2012). https://doi.org/10.1088/0004-637X/753/2/100
S. Birkmann, P. Ferruit, J.A. Valenti, Transiting exoplanet characterization with JWST/NIRSPEC, JWST Proposal ID 1224. Cycle 1 GTO, 2017
J. Blecic, I. Dobbs-Dixon, T. Greene, The implications of 3D thermal structure on 1D atmospheric retrieval. Astrophys. J. 848, 127 (2017). https://doi.org/10.3847/1538-4357/aa8171
M. Bonnefoy, A. Zurlo, J.L. Baudino, P. Lucas, D. Mesa, A.-L. Maire, A. Vigan, R. Galicher, D. Homeier, F. Marocco, First light of the VLT planet finder SPHERE. IV. Physical and chemical properties of the planets around HR8799. Astron. Astrophys. 587, 58 (2016). https://doi.org/10.1051/0004-6361/201526906
M. Brogi, M.R. Line, Retrieving temperatures and abundances of exoplanet atmospheres with high-resolution cross-correlation spectroscopy. Astron. J. 157(3), 114 (2019). https://doi.org/10.3847/1538-3881/aaffd3
B. Charnay, V. Meadows, J. Leconte, 3D modeling of GJ1214b’s atmosphere: vertical mixing driven by an anti-Hadley circulation. Astrophys. J. 813(1), 15 (2015). https://doi.org/10.1088/0004-637X/813/1/15
E.J.W. de Mooij, I.A.G. Snellen, Ground-based K-band detection of thermal emission from the exoplanet TrES-3b. Astron. Astrophys. 493(2), 35–38 (2009). https://doi.org/10.1051/0004-6361:200811239
T.M. Evans, F. Pont, D.K. Sing, S. Aigrain, J.K. Barstow, J.-M. Désert, N. Gibson, K. Heng, H.A. Knutson, A. Lecavelier des Etangs, The deep blue color of HD 189733b: albedo measurements with Hubble Space Telescope/Space Telescope Imaging Spectrograph at visible wavelengths. Astrophys. J. Lett. 772, 16 (2013). https://doi.org/10.1088/2041-8205/772/2/L16
T.M. Evans, D.K. Sing, T. Kataria, J. Goyal, N. Nikolov, H.R. Wakeford, D. Deming, M.S. Marley, D.S. Amundsen, G.E. Ballester, J.K. Barstow, L. Ben-Jaffel, V. Bourrier, L.A. Buchhave, O. Cohen, D. Ehrenreich, A. García Muñoz, G.W. Henry, H. Knutson, P. Lavvas, A. Lecavelier Des Etangs, N.K. Lewis, M. López-Morales, A.M. Mandell, J. Sanz-Forcada, P. Tremblin, R. Lupu, An ultrahot gas-giant exoplanet with a stratosphere. Nature 548, 58–61 (2017). https://doi.org/10.1038/nature23266
T.M. Evans, D.K. Sing, J.M. Goyal, N. Nikolov, M.S. Marley, K. Zahnle, G.W. Henry, J.K. Barstow, M.K. Alam, J. Sanz-Forcada, T. Kataria, N.K. Lewis, P. Lavvas, G.E. Ballester, L. Ben-Jaffel, S.D. Blumenthal, V. Bourrier, B. Drummond, A. García Muñoz, M. López-Morales, P. Tremblin, D. Ehrenreich, H.R. Wakeford, L.A. Buchhave, A. Lecavelier des Etangs, É. Hébrard, M.H. Williamson, An optical transmission spectrum for the ultra-hot Jupiter WASP-121b measured with the Hubble Space Telescope. Astron. J. 156, 283 (2018). https://doi.org/10.3847/1538-3881/aaebff
Y.K. Feng, M.R. Line, J.J. Fortney, K.B. Stevenson, J. Bean, L. Kreidberg, V. Parmentier, The impact of non-uniform thermal structure on the interpretation of exoplanet emission spectra. Astrophys. J. 829(1), 52 (2016). https://doi.org/10.3847/0004-637X/829/1/52
F. Feroz, M.P. Hobson, Multimodal nested sampling: an efficient and robust alternative to Markov Chain Monte Carlo methods for astronomical data analyses. Mon. Not. R. Astron. Soc. 384, 449–463 (2008). https://doi.org/10.1111/j.1365-2966.2007.12353.x
F. Feroz, M.P. Hobson, M. Bridges, MULTINEST: an efficient and robust Bayesian inference tool for cosmology and particle physics. Mon. Not. R. Astron. Soc. 398, 1601–1614 (2009). https://doi.org/10.1111/j.1365-2966.2009.14548.x
F. Feroz, M.P. Hobson, E. Cameron, A.N. Pettitt, Importance nested sampling and the MultiNest algorithm. ArXiv e-prints (2013)
C. Fisher, K. Heng, Retrieval analysis of 38 WFC3 transmission spectra and resolution of the normalization degeneracy. Mon. Not. R. Astron. Soc. 481, 4698–4727 (2018). https://doi.org/10.1093/mnras/sty2550
L.N. Fletcher, G.S. Orton, N.A. Teanby, P.G.J. Irwin, Phosphine on Jupiter and Saturn from Cassini/CIRS. Icarus 202, 543–564 (2009). https://doi.org/10.1016/j.icarus.2009.03.023
J.J. Fortney, K. Lodders, M.S. Marley, R.S. Freedman, A unified theory for the atmospheres of the hot and very hot Jupiters: two classes of irradiated atmospheres. Astrophys. J. 678(2), 1419–1435 (2008). https://doi.org/10.1086/528370
S. Fromang, J. Leconte, K. Heng, Shear-driven instabilities and shocks in the atmospheres of hot Jupiters. Astron. Astrophys. 591, 144 (2016). https://doi.org/10.1051/0004-6361/201527600
J. Goodman, Thermodynamics of atmospheric circulation on hot Jupiters. Astrophys. J. 693(2), 1645–1649 (2009). https://doi.org/10.1088/0004-637X/693/2/1645
T.P. Greene, M.R. Line, C. Montero, J.J. Fortney, J. Lustig-Yaeger, K. Luther, Characterizing transiting exoplanet atmospheres with JWST. Astrophys. J. 817, 17 (2016). https://doi.org/10.3847/0004-637X/817/1/17
C.A. Griffith, Disentangling degenerate solutions from primary transit and secondary eclipse spectroscopy of exoplanets. Philos. Trans. R. Soc. Lond. Ser. A 372(2014), 20130086 (2014). https://doi.org/10.1098/rsta.2013.0086
T. Guillot, On the radiative equilibrium of irradiated planetary atmospheres. Astron. Astrophys. 520, 27 (2010). https://doi.org/10.1051/0004-6361/200913396
K. Haynes, A.M. Mandell, N. Madhusudhan, D. Deming, H. Knutson, Spectroscopic evidence for a temperature inversion in the dayside atmosphere of hot Jupiter WASP-33b. Astrophys. J. 806(2), 146 (2015). https://doi.org/10.1088/0004-637X/806/2/146
C. Helling, P. Woitke, W.-F. Thi, Dust in brown dwarfs and extra-solar planets. I. Chemical composition and spectral appearance of quasi-static cloud layers. Astron. Astrophys. 485, 547–560 (2008). https://doi.org/10.1051/0004-6361:20078220
K. Heng, D. Kitzmann, The theory of transmission spectra revisited: a semi-analytical method for interpreting WFC3 data and an unresolved challenge. Mon. Not. R. Astron. Soc. 470(3), 2972–2981 (2017). https://doi.org/10.1093/mnras/stx1453
K. Heng, J.R. Lyons, Carbon dioxide in exoplanetary atmospheres: rarely dominant compared to carbon monoxide and water in hot, hydrogen-dominated atmospheres. Astrophys. J. 817(2), 149 (2016). https://doi.org/10.3847/0004-637X/817/2/149
K. Heng, K. Menou, P.J. Phillipps, Atmospheric circulation of tidally locked exoplanets: a suite of benchmark tests for dynamical solvers. Mon. Not. R. Astron. Soc. 413(4), 2380–2402 (2011). https://doi.org/10.1111/j.1365-2966.2011.18315.x
K. Heng, W. Hayek, F. Pont, D.K. Sing, On the effects of clouds and hazes in the atmospheres of hot Jupiters: semi-analytical temperature-pressure profiles. Mon. Not. R. Astron. Soc. 420(1), 20–36 (2012). https://doi.org/10.1111/j.1365-2966.2011.19943.x
K. Heng, J.M. Mendonça, J.-M. Lee, Analytical models of exoplanetary atmospheres. II. Radiative transfer via the two-stream approximation. Astrophys. J. Suppl. 215(1), 4 (2014). https://doi.org/10.1088/0067-0049/215/1/4
H.J. Hoeijmakers, D. Ehrenreich, K. Heng, D. Kitzmann, S.L. Grimm, R. Allart, R. Deitrick, A. Wyttenbach, M. Oreshenko, L. Pino, Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b. Nature 560(7719), 453–455 (2018). https://doi.org/10.1038/s41586-018-0401-y
A.R. Howe, A. Burrows, D. Deming, An information-theoretic approach to optimize JWST observations and retrievals of transiting exoplanet atmospheres. Astrophys. J. 835(1), 96 (2017). https://doi.org/10.3847/1538-4357/835/1/96
T.-O. Husser, S. Wende-von Berg, S. Dreizler, D. Homeier, A. Reiners, T. Barman, P.H. Hauschildt, A new extensive library of PHOENIX stellar atmospheres and synthetic spectra. Astron. Astrophys. 553, 6 (2013). https://doi.org/10.1051/0004-6361/201219058
P.G.J. Irwin, N.A. Teanby, R. de Kok, L.N. Fletcher, C.J.A. Howett, C.C.C. Tsang, C.F. Wilson, S.B. Calcutt, C.A. Nixon, P.D. Parrish, The NEMESIS planetary atmosphere radiative transfer and retrieval tool. J. Quant. Spectrosc. Radiat. Transf. 109, 1136–1150 (2008). https://doi.org/10.1016/j.jqsrt.2007.11.006
P.G.J. Irwin, V. Parmentier, J. Taylor, J.K. Barstow, S. Aigrain, G.K.H. Lee, R. Garland, 2.5D retrieval of atmospheric properties from exoplanet phase curves: application to WASP-43b observations. Mon. Not. R. Astron. Soc. 493, 106–125 (2020). https://doi.org/10.1093/mnras/staa238
D. Kitzmann, K. Heng, Optical properties of potential condensates in exoplanetary atmospheres. Mon. Not. R. Astron. Soc. 475(1), 94–107 (2018). https://doi.org/10.1093/mnras/stx3141
L. Kreidberg, J.L. Bean, J.-M. Désert, B. Benneke, D. Deming, K.B. Stevenson, S. Seager, Z. Berta-Thompson, A. Seifahrt, D. Homeier, Clouds in the atmosphere of the super-Earth exoplanet GJ1214b. Nature 505, 69–72 (2014). https://doi.org/10.1038/nature12888
L. Kreidberg, M.R. Line, J.L. Bean, K.B. Stevenson, J.-M. Désert, N. Madhusudhan, J.J. Fortney, J.K. Barstow, G.W. Henry, M.H. Williamson, A detection of water in the transmission spectrum of the hot Jupiter WASP-12b and implications for its atmospheric composition. Astrophys. J. 814(1), 66 (2015). https://doi.org/10.1088/0004-637X/814/1/66
L. Kreidberg, M.R. Line, V. Parmentier, K.B. Stevenson, T. Louden, M. Bonnefoy, J.K. Faherty, K. Stassun, T.G. Beatty, J.L. Bean, J.J. Fortney, A.P. Showman, J.-M. Désert, J. Arcangeli, Global climate and atmospheric composition of the ultra-hot Jupiter WASP-103b from HST and Spitzer phase curve observations. Astron. J. 156(1), 17 (2018). https://doi.org/10.3847/1538-3881/aac3df
J. Krissansen-Totton, R. Garland, P. Irwin, D.C. Catling, Detectability of biosignatures in anoxic atmospheres with the James Webb Space Telescope: a TRAPPIST-1e case study. Astron. J. 156, 114 (2018). https://doi.org/10.3847/1538-3881/aad564
Gravity Collaboration, S. Lacour, M. Nowak, J. Wang, O. Pfuhl, F. Eisenhauer, R. Abuter, A. Amorim, N. Anugu, M. Benisty, First direct detection of an exoplanet by optical interferometry. Astrometry and K-band spectroscopy of HR 8799 e. Astron. Astrophys. 623, 11 (2019). https://doi.org/10.1051/0004-6361/201935253
J.-M. Lee, L.N. Fletcher, P.G.J. Irwin, Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy. Mon. Not. R. Astron. Soc. 420, 170–182 (2012). https://doi.org/10.1111/j.1365-2966.2011.20013.x
G. Lee, I. Dobbs-Dixon, C. Helling, K. Bognar, P. Woitke, Dynamic mineral clouds on HD 189733b. I. 3D RHD with kinetic, non-equilibrium cloud formation. Astron. Astrophys. 594, 48 (2016). https://doi.org/10.1051/0004-6361/201628606
G.K.H. Lee, K. Wood, I. Dobbs-Dixon, A. Rice, C. Helling, Dynamic mineral clouds on HD 189733b. II. Monte Carlo radiative transfer for 3D cloudy exoplanet atmospheres: combining scattering and emission spectra. Astron. Astrophys. 601, 22 (2017). https://doi.org/10.1051/0004-6361/201629804
C. Li, A. Ingersoll, S. Bolton, S. Levin, M. Janssen, S. Atreya, J. Lunine, P. Steffes, S. Brown, T. Guillot, M. Allison, J. Arballo, A. Bellotti, V. Adumitroaie, S. Gulkis, A. Hodges, L. Li, S. Misra, G. Orton, F. Oyafuso, D. Santos-Costa, H. Waite, Z. Zhang, The water abundance in Jupiter’s equatorial zone. Nat. Astron. (2020). https://doi.org/10.1038/s41550-020-1009-3
M.R. Line, V. Parmentier, The influence of nonuniform cloud cover on transit transmission spectra. Astrophys. J. 820, 78 (2016). https://doi.org/10.3847/0004-637X/820/1/78
M.R. Line, X. Zhang, G. Vasisht, V. Natraj, P. Chen, Y.L. Yung, Information content of exoplanetary transit spectra: an initial look. Astrophys. J. 749, 93 (2012). https://doi.org/10.1088/0004-637X/749/1/93
M.R. Line, A.S. Wolf, X. Zhang, H. Knutson, J.A. Kammer, E. Ellison, P. Deroo, D. Crisp, Y.L. Yung, A systematic retrieval analysis of secondary eclipse spectra. I. A comparison of atmospheric retrieval techniques. Astrophys. J. 775, 137 (2013). https://doi.org/10.1088/0004-637X/775/2/137
M.R. Line, H. Knutson, A.S. Wolf, Y.L. Yung, A systematic retrieval analysis of secondary eclipse spectra. II. A uniform analysis of nine planets and their C to O ratios. Astrophys. J. 783, 70 (2014). https://doi.org/10.1088/0004-637X/783/2/70
S. Lines, J. Manners, N.J. Mayne, J. Goyal, A.L. Carter, I.A. Boutle, G.K.H. Lee, C. Helling, B. Drummond, D.M. Acreman, D.K. Sing, Exonephology: transmission spectra from a 3D simulated cloudy atmosphere of HD 209458b. Mon. Not. R. Astron. Soc. 481, 194–205 (2018). https://doi.org/10.1093/mnras/sty2275
R.J. MacDonald, N. Madhusudhan, Signatures of nitrogen chemistry in hot Jupiter atmospheres. Astrophys. J. Lett. 850, 15 (2017). https://doi.org/10.3847/2041-8213/aa97d4
B. Macintosh, J.R. Graham, T. Barman, R.J. De Rosa, Q. Konopacky, M.S. Marley, C. Marois, E.L. Nielsen, L. Pueyo, A. Rajan, Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager. Science 350(6256), 64–67 (2015). https://doi.org/10.1126/science.aac5891
N. Madhusudhan, S. Seager, A temperature and abundance retrieval method for exoplanet atmospheres. Astrophys. J. 707(1), 24 (2009). http://stacks.iop.org/0004-637X/707/i=1/a=24
P. Márquez-Neila, C. Fisher, R. Sznitman, K. Heng, Supervised machine learning for analysing spectra of exoplanetary atmospheres. Nat. Astron. 2, 719–724 (2018). https://doi.org/10.1038/s41550-018-0504-2
J.M. Mendonça, M. Malik, B.-O. Demory, K. Heng, Revisiting the phase curves of WASP-43b: confronting re-analyzed spitzer data with cloudy atmospheres. Astron. J. 155, 150 (2018). https://doi.org/10.3847/1538-3881/aaaebc
K.I. Öberg, R. Murray-Clay, E.A. Bergin, The effects of snowlines on C/O in planetary atmospheres. Astrophys. J. Lett. 743, 16 (2011). https://doi.org/10.1088/2041-8205/743/1/L16
M. Oreshenko, B. Lavie, S.L. Grimm, S.-M. Tsai, M. Malik, B.-O. Demory, C. Mordasini, Y. Alibert, W. Benz, S.P. Quanz, R. Trotta, K. Heng, Retrieval analysis of the emission spectrum of WASP-12b: sensitivity of outcomes to prior assumptions and implications for formation history. Astrophys. J. Lett. 847, 3 (2017). https://doi.org/10.3847/2041-8213/aa8acf
V. Parmentier, T. Guillot, A non-grey analytical model for irradiated atmospheres. I. Derivation. Astron. Astrophys. 562, 133 (2014). https://doi.org/10.1051/0004-6361/201322342
V. Parmentier, J.J. Fortney, A.P. Showman, C. Morley, M.S. Marley, Transitions in the cloud composition of hot Jupiters. Astrophys. J. 828(1), 22 (2016). https://doi.org/10.3847/0004-637X/828/1/22
A. Pinhas, B.V. Rackham, N. Madhusudhan, D. Apai, Retrieval of planetary and stellar properties in transmission spectroscopy with AURA. Mon. Not. R. Astron. Soc. 480(4), 5314–5331 (2018). https://doi.org/10.1093/mnras/sty2209
A. Pinhas, N. Madhusudhan, S. Gandhi, R. MacDonald, H2O abundances and cloud properties in ten hot giant exoplanets. Mon. Not. R. Astron. Soc. 482, 1485–1498 (2019). https://doi.org/10.1093/mnras/sty2544
B. Rackham, N. Espinoza, D. Apai, M. López-Morales, A. Jordán, D.J. Osip, N.K. Lewis, F. Rodler, J.D. Fraine, C.V. Morley, J.J. Fortney, ACCESS I: an optical transmission spectrum of GJ 1214b reveals a heterogeneous stellar photosphere. Astrophys. J. 834(2), 151 (2017). https://doi.org/10.3847/1538-4357/aa4f6c
B.V. Rackham, D. Apai, M.S. Giampapa, The transit light source effect: false spectral features and incorrect densities for M-dwarf transiting planets. Astrophys. J. 853, 122 (2018). https://doi.org/10.3847/1538-4357/aaa08c
E. Rauscher, K. Menou, A general circulation model for gaseous exoplanets with double-gray radiative transfer. Astrophys. J. 750(2), 96 (2012). https://doi.org/10.1088/0004-637X/750/2/96
M. Rocchetto, I.P. Waldmann, O. Venot, P.-O. Lagage, G. Tinetti, Exploring biases of atmospheric retrievals in simulated JWST transmission spectra of hot Jupiters. Astrophys. J. 833, 120 (2016). https://doi.org/10.3847/1538-4357/833/1/120
C.D. Rodgers, Inverse Methods for Atmospheric Sounding (World Scientific, Singapore, 2000)
H. Schwarz, M. Brogi, R. de Kok, J. Birkby, I. Snellen, Evidence against a strong thermal inversion in HD 209458b from high-dispersion spectroscopy. Astron. Astrophys. 576, 111 (2015). https://doi.org/10.1051/0004-6361/201425170
F. Selsis, R.D. Wordsworth, F. Forget, Thermal phase curves of nontransiting terrestrial exoplanets. I. Characterizing atmospheres. Astron. Astrophys. 532, 1 (2011). https://doi.org/10.1051/0004-6361/201116654
K.B. Sheppard, A.M. Mandell, P. Tamburo, S. Gand hi, A. Pinhas, N. Madhusudhan, D. Deming, Evidence for a dayside thermal inversion and high metallicity for the hot Jupiter WASP-18b. Astrophys. J. 850(2), 32 (2017). https://doi.org/10.3847/2041-8213/aa9ae9
D.K. Sing, J.J. Fortney, N. Nikolov, H.R. Wakeford, T. Kataria, T.M. Evans, S. Aigrain, G.E. Ballester, A.S. Burrows, D. Deming, J.-M. Désert, N.P. Gibson, G.W. Henry, C.M. Huitson, H.A. Knutson, A. Lecavelier Des Etangs, F. Pont, A.P. Showman, A. Vidal-Madjar, M.H. Williamson, P.A. Wilson, A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion. Nature 529, 59–62 (2016). https://doi.org/10.1038/nature16068
J. Skilling, Nested sampling for general Bayesian computation. Bayesian Anal. 1(4), 833–859 (2006). https://doi.org/10.1214/06-BA127
K.B. Stevenson, J.L. Bean, N. Madhusudhan, J. Harrington, Deciphering the atmospheric composition of WASP-12b: a comprehensive analysis of its dayside emission. Astrophys. J. 791, 36 (2014a). https://doi.org/10.1088/0004-637X/791/1/36
K.B. Stevenson, J.-M. Désert, M.R. Line, J.L. Bean, J.J. Fortney, A.P. Showman, T. Kataria, L. Kreidberg, P.R. McCullough, G.W. Henry, D. Charbonneau, A. Burrows, S. Seager, N. Madhusudhan, M.H. Williamson, D. Homeier, Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy. Science 346, 838–841 (2014b). https://doi.org/10.1126/science.1256758
J. Tennyson, S. Yurchenko, The ExoMol atlas of molecular opacities. Atoms 6(2), 26 (2018). https://doi.org/10.3390/atoms6020026
G. Tinetti, A. Vidal-Madjar, M.-C. Liang, J.-P. Beaulieu, Y. Yung, S. Carey, R.J. Barber, J. Tennyson, I. Ribas, N. Allard, G.E. Ballester, D.K. Sing, F. Selsis, Water vapour in the atmosphere of a transiting extrasolar planet. Nature 448, 169–171 (2007). https://doi.org/10.1038/nature06002
A. Tsiaras, I.P. Waldmann, T. Zingales, M. Rocchetto, G. Morello, M. Damiano, K. Karpouzas, G. Tinetti, L.K. McKemmish, J. Tennyson, S.N. Yurchenko, A population study of gaseous exoplanets. Astron. J. 155, 156 (2018). https://doi.org/10.3847/1538-3881/aaaf75
T. Zingales, I.P. Waldmann, ExoGAN: retrieving exoplanetary atmospheres using deep convolutional generative adversarial networks. Astron. J. 156(6), 268 (2018). https://doi.org/10.3847/1538-3881/aae77c
Acknowledgements
JKB was supported by a Royal Astronomical Society Research Fellowship during this work. KH thanks the Swiss National Science Foundation, PlanetS National Center of Competence in Research, European Research Council via Consolider Grant number 71620 and MERAC Foundation for partial financial support. We thank the two anonymous reviewers whose comments improved the clarity of this manuscript.
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Understanding the Diversity of Planetary Atmospheres
Edited by François Forget, Oleg Korablev, Julia Venturini, Takeshi Imamura, Helmut Lammer and Michel Blanc
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Barstow, J.K., Heng, K. Outstanding Challenges of Exoplanet Atmospheric Retrievals. Space Sci Rev 216, 82 (2020). https://doi.org/10.1007/s11214-020-00666-x
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DOI: https://doi.org/10.1007/s11214-020-00666-x