arXiv subjects

Hayley Beltz

Publications and source records attributed to Hayley Beltz.

At least 19 recordsLinked to original sources

arXiv2026

Glossy Silicate Clouds on the Scorched Dayside of LTT9779b

Discovered deep within the "Neptunian desert", LTT9779b remains the only known ultra-hot Neptune, prompting significant speculation regarding its unique formation and evolutionary history. Its exceptionally high geometric albedo has previously been attributed either to the presence of clouds or to an extremely metal-rich atmosphere. Here, we present a comprehensive panchromatic analysis of its dayside atmosphere using JWST NIRISS and NIRSpec/G395H observations to characterize its atmospheric structure and composition. Leveraging the exceptional signal-to-noise ratio (S/N) in the observed spectra, we report a 3-to-5$σ$ detection of dayside clouds, with strong evidence for Mg$_2$SiO$_4$(s) (silicate) condensation. This constitutes the first statistically significant detection of clouds on the dayside of a Neptunian-mass exoplanet. We demonstrate that a highly reflective cloud deck, rather than an extremely high-metallicity atmosphere, is the most likely explanation for the planet's anomalously high optical albedo. Furthermore, our atmospheric retrievals yield robust detections of both CO ($\sim$4.88$σ$) and CO$_2$ ($\sim$8.76$σ$), while providing tentative constraints on the H$_2$O abundance and upper limits on SiO, TiO, and VO. Finally, our analysis places a robust constraint on the C/O ratio of 0.984 $\pm$ 0.019. This aligns LTT9779b with other known ultra-hot Jupiters exhibiting super-solar C/O ratios, suggesting a broader trend driven by the sequestration of oxygen-bearing condensates in ultra-hot atmospheres.

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arXiv2026

Effects of Super-rotating Jets on Phase-Resolved Transmission Spectra at High Spectral Resolution

Hot Jupiter atmospheric circulation can be shaped by a range of processes and planetary parameters, including rotation rate, irradiation gradients from tidal synchronization, magnetic effects, gravity, and clouds. Observations of exoplanetary spectral Doppler shifts as a function of phase, made possible with high-resolution spectrographs, can now probe the effects of exoplanetary winds at several points throughout transit. However, these measurements are difficult to interpret, given the variety of relevant atmospheric mechanisms. In this work, we generate high-resolution transmission spectra from two sets of circulation models: self-consistent dynamical models and idealized models that isolate circulation components. We identify how the strength of the jet -- or the absence of one -- alters the resultant net Doppler shifts. We find that the jet strength most prominently affects Doppler shifts during ingress and egress. During mid-transit, the strength of the jet linearly influences the Doppler shifts' slope; however, this effect is generally secondary to the overall blueshifting from planetary rotation. The slope induced by equatorial jets contrasts with the effect of pure day-night flows, which tend to add constant offsets to Doppler shifts during transit. Our modeling shows that jets also impact the cross-correlation function width; faster jets increase velocity dispersion across the limbs. We complement our simulations with semi-analytical arguments indicating that first-order changes of the cross-correlation function centroid and width (but not amplitude) probe thermal and velocity asymmetries. This work provides recommendations for interpreting net Doppler shifts in transmission and connecting these shifts with exoplanets' atmospheric circulation.

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arXiv2026

Magnetic field strengths of hot giant exoplanets consistent with Solar System values

Magnetic fields are ubiquitous in the universe. They play a key role in shaping the activity of stars, the habitability of rocky planets, and the long-term retention of planetary atmospheres. Theoretical scaling laws are largely constrained by the limited set of stars and Solar System planets, leading to a wide range of possible values for hot giant planets outside of the Solar System from fractions of the Jovian field to orders of magnitude larger. Ultra-hot Jupiters, with their highly ionised atmospheres, provide a new avenue to probe magnetic effects, as their atmospheric circulation could be directly sensitive to atmospheric magnetic field strength. Using high-spectral resolution observations targeting the iron lines of ultra-hot Jupiters we measure the Doppler shift and thus the wind speed of seven transiting ultra-hot Jupiters. We find a clear decrease of wind speed with increasing planetary temperature, a trend inconsistent with purely hydrodynamic mechanisms but naturally reproduced by magnetic drag. From this relation we estimate the possible strength of magnetic fields of hot giant planets to at most a few gauss - comparable to the Jovian equatorial field. Our results support the idea that magnetic fields affect the atmospheric circulation of ultra-hot Jupiters and could provide a crucial benchmark for scaling laws used to predict magnetic fields in exoplanets, from hot Jupiters to rocky Earths with additional implications for future direct observations.

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arXiv2026

Unraveling the Mystery of the Peculiar and Young Hot Jupiter CoRoT-2b II: Phase Resolved Emission Spectroscopy with VLT/CRIRES+ and Gemini-S/IGRINS

Hot Jupiters are expected to be tidally locked and synchronously rotating due to their short orbital periods. These conditions create large day-night temperature contrasts and are thought to drive eastward super-rotating jets. Indeed, the majority of hot Jupiters are observed to have the hottest region of the planet either at the substellar point or offset in the eastern direction. However, the full phase curve of CoRoT-2b, observed with the Spitzer Space Telescope, exhibits robust evidence of a western hotspot offset. To determine the origin of this peculiar hotspot offset, we present phase-resolved high-resolution observations of CoRoT-2b from the CRIRES+ spectrograph on the Very Large Telescope (VLT) and the IGRINS spectrograph on Gemini South, covering both pre- and post-eclipse phases (0.34--0.63). We detect the signal from the planet (S/N$>$4) in both pre- and post-eclipse phases separately, and therefore perform separate cross-correlation and retrieval analyses at the two epochs. The phase-resolved retrievals show highly consistent abundances and C/Os, but prefer a hotter and more isothermal temperature-pressure profile at post-eclipse phases, consistent with the phase curve observations that indicated a western hotpsot offset. By testing multiple hypotheses invoked to drive a western hotspot offset, we find the most likely explanation to be sub-synchronous planetary rotation. We measure the planet's rotational broadening to be $2.24\substack{+0.81\\-0.77}$ km s$^{-1}$, whereas the expectation from tidally locked rotation is $4.37\pm0.13$ km s$^{-1}$ (2.6-$σ$ discrepant). Other observations, such as high precision phase curves or eclipse mapping, would help to further confirm the western hotspot offset and sub-synchronous rotation.

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arXiv2026

The Roasting Marshmallows Program with IGRINS on Gemini South V: Atmosphere of MASCARA-1b is Enriched in Refractory Elements

Ultra-hot Jupiters (UHJs; $T_{\rm eq} \gtrsim 2000$ K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b ($T_{\rm eq} \approx 2600$ K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR$>$4) signals from H$_2$O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of $\approx$0.2 dex, retrieving a solar atmospheric metallicity ([M/H]$_\odot$ $= 0.07^{+0.17}_{-0.13}$ $\approx 1.2\times$ solar), a C/O ratio (C/O $= 0.65^{+0.08}_{-0.08}$) consistent with solar value (C/O $=$ 0.59), an enhanced refractory abundance ([R/H]$_\odot$ $= 0.40^{+0.23}_{-0.17} \approx 2.5\times$ solar; $\approx 3.8\times$ stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V]$_\odot$ $= 0.36^{+0.11}_{-0.09}$ $\approx 2.3\times$ solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H$_2$O or H$_2$O-CO snowlines (at 68$\%$ confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68$\%$ confidence). The Mg/Fe is also found to be consistent with stellar value at 95$\%$ confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.

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arXiv2026

Exploring the Impact of Tilted Magnetic Dipoles on the Atmospheric Dynamics of Hot Jupiters: Towards an Improved Magnetohydrodynamic Framework

The atmospheres of hot Jupiters lie in a dynamical regime without a solar system analogue. The strongly irradiated daysides reach temperatures sufficiently hot for substantial thermal ionization of atmospheric species, resulting in flows that can interact with the planetary magnetic field. These magnetic effects can significantly impact wind speeds, atmospheric temperatures, and large-scale circulation patterns. Previous work combining 3D atmospheric models and magnetic prescriptions has shown the impact of magnetic effects on temperature and velocity profiles are dependent on local atmospheric properties as well as the set of assumptions employed by the magnetic prescription. In this work, we examine a commonly employed magnetic model--a perfectly aligned dipole--in 3D General Circulation Models (GCMs) and extend this framework to allow for tilting of the deep-seated internal magnetic dipole field relative to the axis of rotation. We find that the inclusion of a tilted dipole introduces pronounced north-south asymmetries into the temperature profile leading to latitudinally shifted hotpots and deflection of winds that would otherwise be axially symmetric. We additionally simulate JWST/NIRSpec phase curves. We find that the strength of the magnetic field has the most significant effect on the simulated phase curves, with stronger magnetic fields increasing the amplitude of the phase curve and reducing the hot spot offset. Our model can provide qualitative insight into how the magnetic dipole strength or orientation may influence the large scale atmospheric dynamics and represents one of the most sophisticated incorporations of magnetic effects in GCMs for hot Jupiter atmospheres to date.

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arXiv2025

A carbon-rich atmosphere on a windy pulsar planet

A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR\,J2322-2650b, uniquely resembles a hot Jupiter exoplanet due to its minimum density of 1.8 g/cm^3 and its ~1900 K equilibrium temperature. We use JWST to observe PSR J2322-2650b's emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star, we find an atmosphere rich in molecular carbon (C3, C2) with strong westward winds. Our observations open up new exoplanetary chemical (ultra-high C/O and C/N ratios of >100 and >10,000, respectively) and dynamical regimes (ultra-fast rotation with external irradiation) to observational study. The extreme carbon enrichment poses a severe challenge to the current understanding of ``black widow'' companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores.

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arXiv2025

Horizontal and vertical exoplanet thermal structure from a JWST spectroscopic eclipse map

Highly-irradiated giant exoplanets known as "ultra-hot Jupiters" are anticipated to exhibit large variations of atmospheric temperature and chemistry as a function of longitude, latitude, and altitude. Previous observations have hinted at these variations, but the existing data have been fundamentally restricted to probing hemisphere-integrated spectra, thereby providing only coarse information on atmospheric gradients. Here we present a spectroscopic eclipse map of an extrasolar planet, resolving the atmosphere in multiple dimensions simultaneously. We analyze a secondary eclipse of the ultra-hot Jupiter WASP-18b observed with the NIRISS instrument on JWST. The mapping reveals weaker longitudinal temperature gradients than were predicted by theoretical models, indicating the importance of hydrogen dissociation and/or nightside clouds in shaping global thermal emission. Additionally, we identify two thermally distinct regions of the planet's atmosphere: a "hotspot" surrounding the substellar point and a "ring" near the dayside limbs. The hotspot region shows a strongly inverted thermal structure due to the presence of optical absorbers and a water abundance marginally lower than the hemispheric average, in accordance with theoretical predictions. The ring region shows colder temperatures and poorly constrained chemical abundances. Similar future analyses will reveal three-dimensional thermal, chemical, and dynamical properties of a broad range of exoplanet atmospheres.

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arXiv2025

Limb Asymmetries on WASP-39b: A Multi-GCM Comparison of Chemistry, Clouds, and Hazes

With JWST, observing separate spectra of the morning and evening limbs of hot Jupiters has finally become a reality. The first such observation was reported for WASP-39b, where the evening terminator was observed to have a larger transit radius by about 400 ppm and a stronger 4.3 $μ$m CO$_2$ feature than the morning terminator. Multiple factors, including temperature differences, photo/thermochemistry, clouds and hazes, could cause such limb asymmetries. To interpret these new limb asymmetry observations, a detailed understanding of how the relevant processes affect morning and evening spectra grounded in forward models is needed. Focusing on WASP-39b, we compare simulations from five different general circulation models (GCMs), including one simulating disequilibrium thermochemistry and one with cloud radiative feedback, to the recent WASP-39b limb asymmetry observations. We also post-process the temperature structures of all simulations with a 2D photochemical model and one simulation with a cloud microphysics model. Although the temperatures predicted by the different models vary considerably, the models are remarkably consistent in their predicted morning--evening temperature differences. Several equilibrium-chemistry simulations predict strong methane features in the morning spectrum, not seen in the observations. When including disequilibrium processes, horizontal transport homogenizes methane, and these methane features disappear. However, even after including photochemistry and clouds, our models still cannot reproduce the observed ${\sim}2000$ ppm asymmetry in the CO$_2$ feature. A combination of factors, such as varying metallicity and unexplored parameters in cloud models, may explain the discrepancy, emphasizing the need for future models integrating cloud microphysics and feedback across a broader parameter space.

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arXiv2025

Strong NUV Refractory Absorption and Dissociated Water in the Hubble Transmission Spectrum of the Ultra Hot Jupiter KELT-20 b

Ultra hot Jupiters (UHJs) present a promising pathway for drawing a link between a planet's composition and formation history. They retain both refractory and volatiles species in gas phase in their atmospheres, which allows us to place unique constraints on their building blocks. Here, we present the 0.2 - 1.7 $μ$m transmission spectrum of KELT-20 b/MASCARA-2 b taken with the Hubble Space Telescope (HST). Unlike other UHJs around early-type stars, KELT-20 b's orbit is well aligned with its host star's spin axis and we test whether its distinct dynamical configuration is reflected in its composition. We observe a tremendous rise (>10 scale heights) in the planet's transit depth at the near-UV wavelengths, akin to that observed for WASP-178 b and WASP-121 b, and a muted water absorption feature in the near-IR. Our retrievals indicate that the large NUV depth is driven by Fe II and/or SiO and that the water is mostly thermally dissociated. Assuming equilibrium chemistry, we obtain constraints on Z/H and O/H that indicate accretion of volatile-rich solids and/or gas. Both our low resolution spectrum and the refractory elemental ratios from Gandhi et al. 2023 suggest that nightside condensation and rainout are limited to only the most refractory species in the planet's atmosphere. Within the precision limits of the HST spectra, no strong evidence for limb asymmetry is detected. We contextualize this lack of asymmetry by comparing to predictions from general circulation models with and without the effects of kinematic magnetohydrodynamics. Lastly, we find no major differences in the HST transmission spectra of KELT-20 b, WASP-178, and WASP-121 b despite their different dynamical configurations.

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arXiv2025

Assessing robustness and bias in 1D retrievals of 3D Global Circulation Models at high spectral resolution: a WASP-76 b simulation case study in emission

High-resolution spectroscopy (HRS) of exoplanet atmospheres has successfully detected many chemical species and is quickly moving toward detailed characterization of the chemical abundances and dynamics. HRS is highly sensitive to the line shape and position, thus, it can detect three-dimensional (3D) effects such as winds, rotation, and spatial variation of atmospheric conditions. At the same time, retrieval frameworks are increasingly deployed to constrain chemical abundances, pressure-temperature (P-T) structures, orbital parameters, and rotational broadening. To explore the multidimensional parameter space, they need computationally fast models that are consequently mostly one-dimensional (1D). However, this approach risks introducing interpretation bias since the planet's true nature is 3D. We investigate the robustness of this methodology at high spectral resolution by running 1D retrievals on simulated observations in emission within an observational framework using 3D Global Circulation Models of the quintessential HJ WASP-76 b. We find that the retrieval broadly recovers conditions present in the atmosphere, but that the retrieved P-T and chemical profiles are not a homogeneous average of all spatial and phase-dependent information. Instead, they are most sensitive to spatial regions with large thermal gradients, which do not necessarily coincide with the strongest emitting regions. Our results further suggest that the choice of parameterization for the P-T and chemical profiles, as well as Doppler offsets among opacity sources, impact retrieval results. These factors should be carefully considered in future retrieval analyses.

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arXiv2025

The Roasting Marshmallows Program with IGRINS on Gemini South III: Seeing deeper into the metal depleted atmosphere of a gas-giant on the cusp of the hot to ultra-hot Jupiter transition

Ultra-hot Jupiters are a class of gas-giant exoplanets that show a peculiar combination of thermochemical properties in the form of molecular dissociation, atomic ionization, and inverted thermal structures. Atmospheric characterization of gas giants lying in the transitional regime between hot and ultra-hot Jupiters can help in understanding the physical mechanisms that cause the fundamental transition in atmospheres between the two classes of hot gas giants. Using Doppler spectroscopy with IGRINS on Gemini South (1.4 to 2.5 $μ$m), we present the day-side high-resolution spectrum of WASP-122b (T$_{\mathrm{day}}$=2258$ \pm$ 54 K), a gas-giant situated at this transition. We detect the signal from H$_{2}$O, based on which we find that WASP-122b has a significantly metal-depleted atmosphere with metallicity log$_{10}$[Z$_{\mathrm{P}}$/Z$_{\odot}$] = $-$1.48$\pm$0.25 dex (0.033$_{-0.016}^{+0.018}$ $\times$ solar), and solar/sub-solar C/O ratio = 0.36$\pm$0.22 (3$σ$ upper limit 0.82). Drastically low atmospheric metallicity pushes the contribution function to higher pressures, resulting in the planetary spectral lines to originate from a narrow region around 1 bar where the thermal profile is non-inverted. This is inconsistent with solar composition radiative convective equilibrium (RCTE) which predicts an inverted atmosphere with spectral lines in emission. The sub-solar metallicity and solar/sub-solar C/O ratio is inconsistent with expectations from core-accretion. We find the planetary signal to be significantly shifted in K$_{\mathrm{P}}$ and V$_{\mathrm{sys}}$, which is in tension with the predictions from global circulation models and require further investigation. Our results highlight the detailed information content of high-resolution spectroscopy data and their ability to constrain complex atmospheric thermal structures and compositions of exoplanets.

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arXiv2025

Non-ideal MHD simulations of hot Jupiter atmospheres

In Hot Jupiters (HJs), atmospherically induced magnetic fields are expected to play an important role in controlling the wind circulation and in determining their inflated radii. Here we perform 1D plane-parallel magnetohydrodynamic (MHD) simulations of HJ atmospheric columns, using the wind and thermodynamic profiles generated by global circulation models of different exo-planets. We quantitatively investigate the effects of magnetic field winding and Ohmic dissipation (previously considered in several works), with the addition of Hall drift and ambipolar diffusion. The main effect is the magnetic field winding in the full non-linear regime, with local azimuthal fields reaching maximum values up to ${\cal O}(10^2)$ G at the shear layer (typical pressure $\sim 1$ bar), much stronger than the assumed background field generated in the planetary interior. The associated meridional currents undergo Ohmic dissipation, with local heating efficiencies of at least $\sim$ ${10^{-6}}-10^{-3}$ (considering only these shallow layers). In addition to the dominant winding vs. Ohmic balance, the presence of the Hall and ambipolar terms have a non-negligible contribution in shaping and twisting the induced magnetic field at $p\lesssim 1$ bar; however this effect is only apparent for the hottest planets. Our results, though limited by construction to a plane-parallel approximation of the sub-stellar columns and with a simplified setup that cannot consistently include the magnetic drag on the wind, assess the non-linearity and complexity of the magnetic induction in HJs atmospheres, and call for a self-consistent inclusion of MHD effects in Ohmic dissipation studies and circulation models, beyond the often-assumed perturbative regime.

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arXiv2025

Out on a Limb: The Signatures of East-West Asymmetries in Transmission Spectra from General Circulation Models

In the era of JWST, observations of hot Jupiter atmospheres are becoming increasingly precise. As a result, the signature of limb asymmetries due to temperature or abundance differences and the presence of aerosols can now be directly measured using transmission spectroscopy. Using a grid of general circulation models (GCMs) with varying irradiation temperature (1500 K - 4000 K) and prescriptions of cloud formation, we simulate 3D ingress/egress and morning/evening-limb transmission spectra. We aim to assess the impact that clouds, 3D temperature structure, and non-uniform distribution of gases have on the observed spectra, and how these inhomogeneities can be identified. A second goal is to assess the relative merits of two separate methods (ingress/egress v.s. morning/evening-limb spectroscopy) for isolating atmospheric asymmetries. From our models, it is evident that an east-west temperature difference is the leading order effect for producing ingress/egress or morning/evening-limb spectral differences. We additionally find that clouds contribute strongly to the observed limb asymmetry at moderate irradiation temperatures in our grid ($\sim 2000 \mathrm{K} < T_{\mathrm{irr}} < 3500 \mathrm{K}). At lower temperatures clouds equally dominate the optical depth on both limbs, while at higher temperatures the entire terminator region remains cloud-free. We develop limb asymmetry metrics that can be used to assess the degree of east-west asymmetry for a given planet and predict trends in these metrics with respect to irradiation temperature that are indicative of various physical processes. Our results are useful for predicting and diagnosing the signatures of limb asymmetries in JWST spectra.

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arXiv2025

The Effects of Kinematic MHD on the Atmospheric Circulation of Eccentric Hot Jupiters

Hot Jupiters are typically considered to be tidally locked due to their short orbital periods. The extreme irradiation can result in atmospheric species becoming thermally ionized on the dayside, which then interact with the planet's magnetic field by resisting flow across magnetic field lines, shaping the atmospheric structure. However, an eccentric orbit results in temporally dependent irradiation and a non-permanent dayside, as the planet-star distance can change drastically during its orbit. In this paper, we present 3D atmospheric models of TOI-150b, an eccentric (e=0.26), Jupiter-mass 1.75 M_Jup planet whose equilibrium temperature varies from 1300K to 1700K. We conduct simulations for magnetic field strengths ranging from 0-30 Gauss using the kinematic magnetohydrodynamics (MHD) approach. When compared to simulations of the planet assuming a circular orbit, we find that the eccentric orbit results in a strengthened and narrowed equatorial jet, westward winds at mid-latitudes, and a phase-dependent thermal inversion. The strength and magnitude of these effects scale with the chosen global magnetic field strength. We also generate high-resolution (R=100,000) emission spectra to study net Doppler shifts and find inter-orbit spectroscopic variability at moderate magnetic field strengths, as well as decreased Doppler broadening as magnetic field strengths increase. This work represents the first time that the kinematic MHD approach has been applied to an eccentric hot Jupiter and highlights the importance of a locally calculated, temperature dependent magnetic drag prescription for predicting atmospheric structure and resulting spectra.

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arXiv2024

Radiatively Active Clouds and Magnetic Effects Explored in a Grid of Hot Jupiter GCMs

Cloud formation and magnetic effects are both expected to significantly impact the structures and observable properties of hot Jupiter atmospheres. For some hot Jupiters, thermal ionization and condensation can coexist in a single atmosphere, and both processes are important. We present a grid of general circulation models across a wide range of irradiation temperatures with and without incorporating the effects of magnetism and cloud formation to investigate how these processes work in tandem. We find that clouds are present in the atmosphere at all modeled irradiation temperatures, while magnetic effects are negligible for planets with irradiation temperatures cooler than 2000 K. At and above this threshold, clouds and magnetic fields shape atmospheres together, with mutual feedback. Models that include magnetism, through their influence on the temperature structure, produce more longitudinally symmetric dayside cloud coverage and more equatorially concentrated clouds on the nightside and morning terminator. To indicate how these processes would affect observables, we generate bolometric thermal and reflected phase curves from these models. The combination of clouds and magnetic effects increases thermal phase curve amplitudes and decreases peak offsets more than either process does individually.

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arXiv2024

The Roasting Marshmallows Program with IGRINS on Gemini South II -- WASP-121 b has super-stellar C/O and refractory-to-volatile ratios

A primary goal of exoplanet science is to measure the atmospheric composition of gas giants in order to infer their formation and migration histories. Common diagnostics for planet formation are the atmospheric metallicity ([M/H]) and the carbon-to-oxygen (C/O) ratio as measured through transit or emission spectroscopy. The C/O ratio in particular can be used to approximately place a planet's initial formation radius from the stellar host, but a given C/O ratio may not be unique to formation location. This degeneracy can be broken by combining measurements of both the C/O ratio and the atmospheric refractory-to-volatile ratio. We report the measurement of both quantities for the atmosphere of the canonical ultra hot Jupiter WASP-121 b using the high resolution (R=45,000) IGRINS instrument on Gemini South. Probing the planet's direct thermal emission in both pre- and post-secondary eclipse orbital phases, we infer that WASP-121 b has a significantly super-stellar C/O ratio of 0.70$^{+0.07}_{-0.10}$ and a moderately super-stellar refractory-to-volatile ratio at 3.83$^{+3.62}_{-1.67} \times$ stellar. This combination is most consistent with formation between the soot line and H$_2$O snow line, but we cannot rule out formation between the H$_2$O and CO snow lines or beyond the CO snow line. We also measure velocity offsets between H$_2$O, CO, and OH, potentially an effect of chemical inhomogeneity on the planet day side. This study highlights the ability to measure both C/O and refractory-to-volatile ratios via high resolution spectroscopy in the near-infrared H and K bands.

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arXiv2024

Comparative Planetology of Magnetic Effects in Ultrahot Jupiters: Trends in High Resolution Spectroscopy

Ultrahot Jupiters (UHJs), being the hottest class of exoplanets known, provide a unique laboratory for testing atmospheric interactions with internal planetary magnetic fields at a large range of temperatures. Thermal ionization of atmospheric species on the dayside of these planets results in charged particles becoming embedded in the planet's mostly neutral wind. The charges will resist flow across magnetic field lines as they are dragged around the planet and ultimately alter the circulation pattern of the atmosphere. We model this process to study this effect on high resolution emission and transmission spectra in order to identify observational signatures of the magnetic circulation regime that exist across multiple UHJs. Using a state-of-the-art kinematic MHD/active drag approach in a 3D atmospheric model, we simulate three different ultrahot Jupiters with and without magnetic effects. We post-process these models to generate high resolution emission and transmission spectra and explore trends in net Doppler shift as a function of phase. In emission spectra, we find that the net Doppler shift before and after secondary eclipse can be influenced by the presence of magnetic drag and wavelength choice. Trends in transmission spectra show our active drag models consistently produce a unique shape in their Doppler shift trends that differs from the models without active drag. This work is a critical theoretical step to understanding how magnetic fields shape the atmospheres of UHJs and provides some of the first predictions in high resolution spectroscopy for observing these effects.

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