A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b

Coulombe, Louis-Philippe; Benneke, Björn; Challener, Ryan C.; Piette, Anjali A. A.; Wiser, Lindsey S.; Mansfield, Megan; Macdonald, Ryan; Beltz, Hayley; Feinstein, Adina D.; Radica, Michael; Savel, Arjun B.; Santos, Leonardo A. Dos; Bean, Jacob L.; Parmentier, Vivien; Wong, Ian C. K.; Rauscher, Emily; Komacek, Thaddeus D.; Kempton, Eliza M.-R.; Tan, Xianyu; Hammond, Mark; Lewis, Neil T.; Line, Michael R.; Lee, Elspeth K. H.; Shivkumar, Hinna; Crossfield, Ian J. M.; Nixon, Matthew C.; Rackham, Benjamin V.; Wakeford, Hannah R.; Welbanks, Luis; Zhang, Xi; Batalha, Natalie M.; Berta-Thompson, Zachory K.; Changeat, Quentin; Désert, Jean-Michel; Espinoza, N.; Goyal, Jayesh; Harrington, Joseph; Knutson, Heather A.; Kreidberg, Laura; López‐Morales, Mercedes; Shporer, Avi; Sing, David K.; Stevenson, Kevin B.; Aggarwal, Keshav; Ahrer, Eva-Maria; Alam, Munazza K.; Bell, Taylor; Blecic, Jasmina; Cáceres, C.; Carter, Aarynn L.; Casewell, Sarah L.; Crouzet, Nicolas; Cubillos, Patricio; Decin, L.; Fortney, Jonathan J.; Gibson, Neale P.; Heng, Kevin; Henning, Thomas; Iro, Nicolas; Kendrew, Sarah; Lagage, Pierre-Olivier; Leconte, Jérémy; Lendl, M.; Lothringer, Joshua D.; Mancini, L.; Evans, T. M.; Molaverdikhani, Karan; Nikolov, Nikolay; Ohno, Kazumasa; Πάλλη, Ε.; Piaulet, Caroline; Redfield, Seth; Roy, Pierre-Alexis; Tsai, Shang-Min; Venot, Olivia; Wheatley, P. J.

doi:10.48550/arxiv.2301.08192

Cited by 5 publications

(2 citation statements)

References 71 publications

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“…For reference, A g (λ) = 2/3 for a perfectly reflecting Lambert sphere, 3/4 for a purely Rayleigh scattering atmosphere, and could reach >1 for anisotropically scattering atmospheres, though that would invalidate the assumption inherent in Equation (8) (Cahoy et al 2010). While the precision of a few tens of parts per million appears to be above the noise floor of JWST's near-IR instruments (Rustamkulov et al 2022;Coulombe et al 2023;Ahrer et al 2023;Schlawin et al 2023), multiple transits and spectral binning are likely needed to reach the necessary signalto-noise ratio for detecting reflected light. However, without a self-consistent computation of the thermal emission of the planet (Section 4.1), the wavelengths at which reflected light dominates over thermal emission are uncertain.…”

Section: Outlook For Future Observationsmentioning

confidence: 99%

The Hazy and Metal-rich Atmosphere of GJ 1214 b Constrained by Near- and Mid-infrared Transmission Spectroscopy

Piette

Steinrueck

Nixon

et al. 2023

ApJ

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The near-infrared transmission spectrum of the warm sub-Neptune exoplanet GJ 1214 b has been observed to be flat and featureless, implying a high metallicity atmosphere with abundant aerosols. Recent JWST MIRI Low Resolution Spectrometer observations of a phase curve of GJ 1214 b showed that its transmission spectrum is flat out into the mid-infrared. In this paper, we use the combined near- and mid-infrared transmission spectrum of GJ 1214 b to constrain its atmospheric composition and aerosol properties. We generate a grid of photochemical haze models using an aerosol microphysics code for a number of background atmospheres spanning metallicities from 100 to 1000× solar, as well as a steam atmosphere scenario. The flatness of the combined data set largely rules out atmospheric metallicities ≤300× solar due to their large corresponding molecular feature amplitudes, preferring values ≥1000× solar and column haze production rates ≥10−10 g cm−2 s−1. The steam atmosphere scenario with similarly high haze production rates also exhibits sufficiently small molecular features to be consistent with the transmission spectrum. These compositions imply that atmospheric mean molecular weights ≥15 g mol−1 are needed to fit the data. Our results suggest that haze production is highly efficient on GJ 1214 b and could involve non-hydrocarbon, non-nitrogen haze precursors. Further characterization of GJ 1214 b’s atmosphere would likely require multiple transits and eclipses using JWST across the near- and mid-infrared, potentially complemented by ground-based high-resolution transmission spectroscopy.

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Section: Outlook For Future Observationsmentioning

confidence: 99%

The Hazy and Metal-rich Atmosphere of GJ 1214 b Constrained by Near- and Mid-infrared Transmission Spectroscopy

Piette

Steinrueck

Nixon

et al. 2023

ApJ

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“…The coefficients on the mapping components are changed by 1% by orbital uncertainties versus fixed uncertainties for HD 189733 b. Uncertain orbital parameters (other than eccentricity) also have a negligible effect on the eclipse map recovered for WASP-18 b, with maps well within uncertainties even when the impact parameter, semimajor axis, and eclipse time were varied by ±1σ (Coulombe et al 2023).…”

Section: Uncertain Orbital Parametersmentioning

confidence: 95%

Planet Eclipse Mapping with Long-term Baseline Drifts

Schlawin¹,

Challener

Mansfield³

et al. 2023

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High-precision lightcurves combined with eclipse-mapping techniques can reveal the horizontal and vertical structure of a planet’s thermal emission and the dynamics of hot Jupiters. Someday, they even may reveal the surface maps of rocky planets. However, inverting lightcurves into maps requires an understanding of the planet, star, and instrumental trends because they can resemble the gradual flux variations as the planet rotates (i.e., partial phase curves). In this work, we simulate lightcurves with baseline trends and assess the impact on planet maps. Baseline trends can be erroneously modeled by incorrect astrophysical planet map features, but there are clues to avoid this pitfall in both the residuals of the lightcurve during eclipse and sharp features at the terminator of the planet. Models that use a Gaussian process or polynomial to account for a baseline trend successfully recover the input map even in the presence of systematics but with worse precision for the m = 1 spherical harmonic terms. This is also confirmed with the ThERESA eigencurve method where fewer lightcurve terms can model the planet without correlations between the components. These conclusions help aid the decision on how to schedule observations to improve map precision. If the m = 1 components are critical, such as measuring the east/west hot-spot shift on a hot Jupiter, better characterization of baseline trends can improve the m = 1 terms’ precision. For latitudinal north/south information from m ≠ 1 mapping terms, it is preferable to obtain high signal to noise at ingress/egress with more eclipses.

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Revealing the atmospheres of highly irradiated exoplanets: from ultra-hot Jupiters to rocky worlds

Mansfield

2023

Astrophys Space Sci

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Spectroscopy of transiting exoplanets has revealed a wealth of information about their atmospheric compositions and thermal structures. In particular, studies of highly irradiated exoplanets at temperatures much higher than those found in our solar system have provided detailed information on planetary chemistry and physics because of the high level of precision which can be obtained from such observations. Here we use a variety of techniques to study the atmospheres of highly irradiated transiting exoplanets and address three large, open questions in exoplanet atmosphere spectroscopy. First, we use secondary eclipse and phase curve observations to investigate the thermal structures and heat redistribution of ultra-hot Jupiters, the hottest known exoplanets. We demonstrate how these planets form an unique class of objects influenced by high-temperature chemical effects such as molecular dissociation and H− opacity. Second, we use observations of helium in the upper atmosphere of the exo-Neptune HAT-P-11b to probe atmospheric escape processes. Third, we develop tools to interpret JWST observations of highly irradiated exoplanets, including a data analysis pipeline to perform eclipse mapping of hot Jupiters and a method to infer albedos of and detect atmospheres on hot, terrestrial planets. Finally, we discuss remaining open questions in the field of highly irradiated exoplanets and opportunities to advance our understanding of these unique bodies in the coming years.

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A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b

Cited by 5 publications

References 71 publications

The Hazy and Metal-rich Atmosphere of GJ 1214 b Constrained by Near- and Mid-infrared Transmission Spectroscopy

The Hazy and Metal-rich Atmosphere of GJ 1214 b Constrained by Near- and Mid-infrared Transmission Spectroscopy

Planet Eclipse Mapping with Long-term Baseline Drifts

Revealing the atmospheres of highly irradiated exoplanets: from ultra-hot Jupiters to rocky worlds

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