Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Beltz, Hayley; Rauscher, Emily; Kempton, Eliza M.-R.; Malsky, Isaac; Grace, Ochs,; Arora, Mireya; Savel, Arjun B.

doi:10.3847/1538-3881/ac897b

“…In our analysis, the most evident shift is between CO and H 2 O. Beltz et al (2022) modeled the effects of magnetic drag and 3D atmospheric circulation for WASP-76 b, another UHJ. They indeed predict a differential radial velocity between two wavelength regions dominated by water (1.2 μm) and CO (2.3 μm).…”

Section: Are the Molecules Tracing Different Dynamics?mentioning

confidence: 98%

The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultrahot Jupiter WASP-18 b

Brogi

¹

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Emeka-Okafor

²

,

Line

³

et al. 2023

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We present high-resolution dayside thermal emission observations of the exoplanet WASP-18 b using IGRINS on Gemini South. We remove stellar and telluric signatures using standard algorithms, and we extract the planet signal via cross-correlation with model spectra. We detect the atmosphere of WASP-18 b at a signal-to-noise ratio (S/N) of 5.9 using a full chemistry model, measure H2O (S/N = 3.3), CO (S/N = 4.0), and OH (S/N = 4.8) individually, and confirm previous claims of a thermal inversion layer. The three species are confidently detected (>4σ) with a Bayesian inference framework, which we also use to retrieve abundance, temperature, and velocity information. For this ultrahot Jupiter (UHJ), thermal dissociation processes likely play an important role. Retrieving abundances constant with altitude and allowing the temperature–pressure profile to adjust freely results in a moderately super-stellar carbon-to-oxygen ratio (C/O = 0.75 − 0.17 + 0.14 ) and metallicity ([M/H] = 1.03 − 1.01 + 0.65 ). Accounting for undetectable oxygen produced by thermal dissociation leads to C/O = 0.45 − 0.10 + 0.08 and [M/H] = 1.17 − 1.01 + 0.66 . A retrieval that assumes radiative–convective–thermochemical equilibrium and naturally accounts for thermal dissociation constrains C/O < 0.34 (2σ) and [M/H] = 0.48 − 0.29 + 0.33 , in line with the chemistry of the parent star. Looking at the velocity information, we see a tantalizing signature of different Doppler shifts at the level of a few kilometers per second for different molecules, which might probe dynamics as a function of altitude and/or location on the planet disk. Our results demonstrate that ground-based, high-resolution spectroscopy at infrared wavelengths can provide meaningful constraints on the compositions and climate of highly irradiated planets. This work also elucidates potential pitfalls with commonly employed retrieval assumptions when applied to the spectra of UHJs.

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“…When observed using this technique, features in the planet continuum are lost, but the phase-resolved Doppler shift and Doppler broadening of emission or reflection lines uniquely constrains the orbit of the planet, as well as its rotation and dynamics (Collier Cameron et al 1999;Kawahara 2012;Brogi et al 2013;Snellen et al 2014). This is supported by dedicated theoretical studies, which, applying radiative transfer to general circulation models (GCMs), show that the combination of inhomogeneous specific intensity, rotation, and winds imprints kilometre-per-second level Doppler shifts and significant distortions in the line shapes and strengths (Zhang et al 2017;Beltz et al 2022a). However, two challenges have so far hindered the use of this technique.…”

Section: Introductionmentioning

confidence: 94%

“…The effect is symmetric for ϕ > 0.5. The discontinuity at ϕ = 0 is due to our assumption that the nightside is not contributing to the emission (Beltz et al 2022a). This reasoning is easily extended to the case of eastward wind, which simply adds to the planet rotation velocity, while the day-to-night flow case is slightly more complicated, but can be understood with similar reasoning.…”

Section: The Climate Of Kelt-9bmentioning

confidence: 99%

“…This has already been shown by computing HRS spectra starting from the GCMs of irradiated planets (e.g. Zhang et 2017;Beltz et al 2021Beltz et al , 2022a. Unfortunately, such simulations are time-consuming, and using them for data comparison over a large parameter space is currently unrealistic.…”

Section: Hrs Phase Curves As a New Tool For Exoplanet Atmosphere Char...mentioning

confidence: 99%

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The GAPS Programme at TNG

Pino

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,

Brogi

²

,

Désert

³

et al. 2022

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Aims. We present a novel method for studying the thermal emission of exoplanets as a function of orbital phase at very high spectral resolution, and use it to investigate the climate of the ultra-hot Jupiter KELT-9b. Methods. We combine three nights of HARPS-N and two nights of CARMENES optical spectra, covering orbital phases between quadratures (0.25 < ϕ < 0.75), when the planet shows its day-side hemisphere with different geometries. We co-add the signal of thousands of Fe i lines through cross-correlation, which we map to a likelihood function. We investigate the phase-dependence of two separate observable quantities, namely (i) the line depths of Fe i and (ii) their Doppler shifts, introducing a new method that exploits the very high spectral resolution of our observations. Results. We confirm a previous detection of Fe i emission, and demonstrate a precision of 0.5 km s −1 on the orbital properties of KELT-9b when combining all nights of observations. By studying the phase-resolved Doppler shift of Fe i lines, we detect an anomaly in the planet's orbital radial velocity well-fitted with a slightly eccentric orbital solution (e = 0.016 ± 0.003, ω = 150 +13 • −11 , 5σ preference). However, we argue that this anomaly is caused by atmospheric circulation patterns, and can be explained if neutral iron gas is advected by day-to-night atmospheric wind flows of the order of a few km s −1 . We additionally show that the Fe i emission line depths are symmetric around the substellar point within 10 • (2σ), possibly indicating the lack of a large hot-spot offset at the altitude probed by neutral iron emission lines. Finally, we do not obtain a significant preference for models with a strong phase-dependence of the Fe i emission line strength. We show that these results are qualitatively compatible with predictions from general circulation models (GCMs) for ultra-hot Jupiter planets. Conclusions. Very high-resolution spectroscopy phase curves are of sufficient sensitivity to reveal a phase dependence in both the line depths and their Doppler shifts throughout the orbit. They constitute an under-exploited treasure trove of information that is highly complementary to space-based phase curves obtained with HST and JWST, and open a new window onto the still poorly understood climate and atmospheric structure of the hottest planets known to date.

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“…As shown in Figure 4, the abundance of CO is relatively stable between 1000 and 3500 K. Beltz et al (2022) note that this stability holds over the temperature-pressure range of the observable atmosphere of the ultrahot Jupiter WASP-76 b. Indeed, this feature remains true over the general temperaturepressure range of ultrahot Jupiters.…”

Section: Co As a Baseline Moleculementioning

confidence: 68%

Diagnosing Limb Asymmetries in Hot and Ultrahot Jupiters with High-resolution Transmission Spectroscopy

Savel

¹

,

Kempton

²

,

Rauscher

³

et al. 2023

ApJ

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Due to their likely tidally synchronized nature, (ultra)hot Jupiter atmospheres should experience strongly spatially heterogeneous instellation. The large irradiation contrast and resulting atmospheric circulation induce temperature and chemical gradients that can produce asymmetries across the eastern and western limbs of these atmospheres during transit. By observing an (ultra)hot Jupiter’s transmission spectrum at high spectral resolution, these asymmetries can be recovered—namely through net Doppler shifts originating from the exoplanet’s atmosphere yielded by cross-correlation analysis. Given the range of mechanisms at play, identifying the underlying cause of observed asymmetry is nontrivial. In this work, we explore sources and diagnostics of asymmetries in high-resolution cross-correlation spectroscopy of hot and ultrahot Jupiters using both parameterized and self-consistent atmospheric models. If an asymmetry is observed, we find that it can be difficult to attribute it to equilibrium chemistry gradients because many other processes can produce asymmetries. Identifying a molecule that is chemically stable over the temperature range of a planetary atmosphere can help establish a baseline to disentangle the various potential causes of limb asymmetries observed in other species. We identify CO as an ideal molecule, given its stability over nearly the entirety of the ultrahot Jupiter temperature range. Furthermore, we find that if limb asymmetry is due to morning terminator clouds, blueshifts for a number of species should decrease during transit. Finally, by comparing our forward models to those of Kesseli et al., we demonstrate that binning high-resolution spectra into two phase bins provides a desirable trade-off between maintaining signal to noise and resolving asymmetries.

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Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Cited by 16 publications

References 113 publications

The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultrahot Jupiter WASP-18 b

The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultrahot Jupiter WASP-18 b

The GAPS Programme at TNG

Diagnosing Limb Asymmetries in Hot and Ultrahot Jupiters with High-resolution Transmission Spectroscopy

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