An absolute sodium abundance for a cloud-free ‘hot Saturn’ exoplanet

Nikolov, Nikolay; Sing, David K.; Fortney, Jonathan J.; Goyal, Jayesh; Drummond, Benjamin; Evans, T. M.; Gibson, Neale P.; Mooij, Ernst de; Rustamkulov, Zafar; Wakeford, Hannah R.; Smalley, B.; Burgasser, Adam J.; Hellier, C.; Helling, Christiane; Mayne, Nathan J.; Madhusudhan, Nikku; Kataria, Tiffany; Baines, John D.; Carter, Aarynn L.; Ballester, G. E.; Barstow, Joanna K.; McCleery, J.; Spake, Jessica

doi:10.1038/s41586-018-0101-7

Cited by 156 publications

(193 citation statements)

References 75 publications

(112 reference statements)

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“…A major development in recent years has been the ability to detect these species routinely and robustly using ground-based facilities. While the first ground-based Na/K detections were already made a decade ago (e.g., 214), recent observations are demonstrating nearly space-quality spectra from large ground-based telescopes such as VLT and GTC (193,53). Besides Na and K, the first potential inference of Li was also made from the ground recently using the GTC (53).…”

Section: Chemical Compositionsmentioning

confidence: 99%

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Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects

Madhusudhan

2019

Annu. Rev. Astron. Astrophys.

306

227

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Exoplanetary science is on the verge of an unprecedented revolution. The thousands of exoplanets discovered over the past decade have most recently been supplemented by discoveries of potentially habitable planets around nearby low-mass stars. Currently, the field is rapidly progressing towards detailed spectroscopic observations to characterise the atmospheres of these planets. While various surveys from space and ground are expected to detect numerous more exoplanets orbiting nearby stars, the imminent launch of JWST along with large groundbased facilities are expected to revolutionise exoplanetary spectroscopy. Such observations, combined with detailed theoretical models and inverse methods, provide valuable insights into a wide range of physical processes and chemical compositions in exoplanetary atmospheres. Depending on the planetary properties, the knowledge of atmospheric compositions can also place important constraints on planetary formation and migration mechanisms, geophysical processes and, ultimately, biosignatures. In the present review, we will discuss the modern and future landscape of this frontier area of exoplanetary atmospheres. We will start with a brief review of the area, emphasising the key insights gained from different observational methods and theoretical studies. This is followed by an in-depth discussion of the state-of-the-art, challenges, and future prospects in three forefront branches of the area. 2 N. Madhusudhan 6 N. Madhusudhan 28 N. Madhusudhan 42 N. Madhusudhan

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Section: Chemical Compositionsmentioning

confidence: 99%

“…4. In particular, ground-based transit spectroscopy at both low-resolution and high-resolution will continue to provide robust detections of several chemical species such as Na, K, TiO, and He (e.g., 232,193). Such detections can be made using instruments on existing large ground-based telescopes (e.g.…”

Section: Exoplanetary Atmospheres With Current Facilitiesmentioning

confidence: 99%

Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects

Madhusudhan

2019

Annu. Rev. Astron. Astrophys.

306

227

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“…Condensation can be treated either locally or using a rainout approach (see Goyal et al 2019). The planetary spectrum viewed by an external observer is produced as output, allowing ATMO to be used for inferring atmospheric properties from primary transit (Evans et al 2016(Evans et al , 2018Wakeford et al 2017Wakeford et al , 2018Nikolov et al 2018a;Alam et al 2018) and secondary eclipse (Evans et al 2017;Nikolov et al 2018b) measurements. We previously used ATMO in Evans et al (2017) to analyze the G141, z , and IRAC 3.6 µm emission data for WASP-121b.…”

Section: Atmosphere Modeling Of the Dayside Hemispherementioning

confidence: 99%

An emission spectrum for WASP-121b measured across the 0.8–1.1 μm wavelength range using the Hubble Space Telescope

Evans

Sing

Goyal

et al. 2019

Monthly Notices of the Royal Astronomical Society

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WASP-121b is a transiting gas giant exoplanet orbiting close to its Roche limit, with an inflated radius nearly double that of Jupiter and a dayside temperature comparable to a late M dwarf photosphere. Secondary eclipse observations covering the 1.1-1.6 µm wavelength range have revealed an atmospheric thermal inversion on the dayside hemisphere, likely caused by high altitude absorption at optical wavelengths. Here we present secondary eclipse observations made with the Hubble Space Telescope Wide Field Camera 3 spectrograph that extend the wavelength coverage from 1.1 µm down to 0.8 µm. To determine the atmospheric properties from the measured eclipse spectrum, we performed a retrieval analysis assuming chemical equilibrium, with the effects of thermal dissociation and ionization included. Our best-fit model provides a good fit to the data with reduced χ 2 ν = 1.04. The data diverge from a blackbody spectrum and instead exhibit emission due to H − shortward of 1.1 µm. The best-fit model does not reproduce a previously reported bump in the spectrum at 1.25µm, possibly indicating this feature is a statistical fluctuation in the data rather than a VO emission band as had been tentatively suggested. We estimate an atmospheric metallicity of [M/H] = 1.09 +0.57 −0.69 , and fit for the carbon and oxygen abundances separately, obtaining [C/H] = −0.29 +0.61 −0.48 and [O/H] = 0.18 +0.64 −0.60 . The corresponding carbon-tooxygen ratio is C/O = 0.49 +0.65 −0.37 , which encompasses the solar value of 0.54, but has a large uncertainty.

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“…Transmission spectra of transiting planets have mostly been obtained through multiband photometric transit observations and spectro-photometric observations. Transmission spectroscopy has been proven to be the most powerful technique to detect broadband and narrow-band features due to the absorption or scattering of starlight by the atoms, molecules, and particles present in the planetary atmosphere (e.g., Sing 2010;Kreidberg et al 2014;Wyttenbach et al 2015;Sing et al 2016;Mallonn & Strassmeier 2016;Lendl et al 2017;Nikolov et al 2018;Chen et al 2018;Keles et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Stellar activity consequence on the retrieved transmission spectra through chromatic Rossiter-McLaughlin observations

Boldt

Oshagh

Mallonn

et al. 2020

A&A

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Mostly multiband photometric transit observations have been used so far to retrieve broadband transmission spectra of transiting exoplanets in order to study their atmosphere. An alternative method has been proposed and has only been used once to recover transmission spectra using chromatic Rossiter-McLaughlin observations. Stellar activity has been shown to potentially imitate narrow and broadband features in the transmission spectra retrieved from multiband photometric observations; however, there has been no study regarding the influence of stellar activity on the retrieved transmission spectra through chromatic Rossiter-McLaughlin. In this study with the modified SOAP3.0 tool, we consider different types of stellar activity features (spots and plages), and we generated a large number of realistic chromatic Rossiter-McLaughlin curves for different types of planets and stars. We were then able to retrieve their transmission spectra to evaluate the impact of stellar activity on them. We find that chromatic Rossiter-McLaughlin observations are also not immune to stellar activity, which can mimic broadband features, such as Rayleigh scattering slope, in their retrieved transmission spectra. We also find that the influence is independent of the planet radius, orbital orientations, orbital period, and stellar rotation rate. However, more general simulations demonstrate that the probability of mimicking strong broadband features is lower than 25% and that can be mitigated by combining several Rossiter-McLaughlin observations obtained during several transits.

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An absolute sodium abundance for a cloud-free ‘hot Saturn’ exoplanet

Cited by 156 publications

References 75 publications

Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects

Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects

An emission spectrum for WASP-121b measured across the 0.8–1.1 μm wavelength range using the Hubble Space Telescope

Stellar activity consequence on the retrieved transmission spectra through chromatic Rossiter-McLaughlin observations

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