arXiv subjects

Giuseppe Morello

Publications and source records attributed to Giuseppe Morello.

At least 19 recordsLinked to original sources

arXiv2026

Mass constraints for the K2-223 system planets: An ultra-short-period sub-Earth, a short-period super-Earth, and a tentative long-period giant planet

We present mass constraints of two short-period, terrestrial-sized planets transiting K2-223, based on high-precision radial velocity measurements from HARPS-N and ESPRESSO, as well as a tentative indication of an outer, Jupiter-like planet orbiting the G1V dwarf K2-223. With a radius of $R_\mathrm{b}=0.79\pm0.10$ $\mathrm{R_{\oplus}}$ and 3-$\sigma$ upper mass limit $M_\mathrm{b}<2.8$ $\mathrm{M_{\oplus}}$, K2-223 b belongs to the small group of known sub-Earth planets and is currently the smallest known ultra-short-period (USP) planet ($P_\mathrm{b}\approx$ 0.5 day) transiting a solar-type star. With a radius of $R_\mathrm{c}=1.41\pm0.15$ $\mathrm{R_{\oplus}}$, a mass of $M_\mathrm{c}=4.2\pm1.3$ $\mathrm{M_{\oplus}}$ and a density of $\rho_\mathrm{c}=8.3\pm3.7$ $\mathrm{g\,cm^{-3}}$, K2-223 c is a short-period ($P_\mathrm{c}\approx$ 4.5 days) super-Earth. Thanks to almost six and a half years of radial velocity monitoring of K2-223 with the HARPS-N spectrograph, we identified a tentative giant planet with an orbital period of $P_\mathrm{d}=4.53^{+0.32}_{-0.34}$ $\mathrm{years}$ and a minimum mass of $1.29^{+0.23}_{-0.17}$ $\mathrm{M_{\rm Jup}}$. Two close-in small planets accompanied by a distant candidate Jupiter-like companion would make K2-223 a system with a rare architecture, valuable for testing scenarios of planetary formation and evolution. The extreme proximity of K2-223 b to the parent star necessitates the consideration of relativistic and tidal perturbations to Newtonian gravity. We discuss the timescales and amplitudes of these effects in the context of the RV model and dynamical simulations of the K2-223 multiple-planet system. We also present a parametrisation of the planets with directly measured masses, radii, and bulk densities in terms of the orbital period normalised by the Roche period, providing an alternative representation in the context of the Neptune desert.

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arXiv2026

A new window in time: a mid-infrared slit spectroscopy mode for precision time-series astronomy with JWST/MIRI

The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) provides Low Resolution Spectroscopy (LRS) over 5-12 um at a resolving power of R ~ 100. To date, all MIRI LRS time-series observations (TSOs) have been carried out in slitless mode, since long-duration pointing stability within the narrow 4.7'' x 0.51'' slit could not previously be guaranteed, leading to the possibility of degraded TSOs due to jitter. Commissioning activities established the telescope jitter to be less than 1 milliarcsecond (mas), four times less than the initial requirement. It was, therefore, worth assessing the suitability of the MIRI LRS slit as a TSO mode for precision time-domain science; this is the aim of the Cycle 3 program (PID 6219, PI: A. Dyrek). We observed a transit of the exoplanet HAT-P-12b over ~10 hours and compared the results to archival slitless observations of the same target (PID 1281, PI: P.-O. Lagage). Two independent data reductions of the transit spectra of both slit and slitless configurations are consistent within 1 sigma, validating the feasibility of the new mode. A joint fit of the slit and slitless observations confirms the presence of a spectral feature near 7.5 um. Using measured JWST pointing variations, we estimated slit-loss variations to be smaller than 40 ppm at 10 um. The drawback of the slitless mode is a higher background. Compellingly, the slit background is ~ 38 times lower on average than in slitless mode, improving sensitivity for faint targets (Jmag ~ 13-15). We also identified time-correlated noise unique to the slit dataset at long wavelengths, which requires further investigation. This new capability of TSOs in slit mode, which will be supported in Cycle 7 (in 2028), opens a new avenue for precision time-series astronomy for faint targets with JWST/MIRI.

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arXiv2026

Towards a Comprehensive Understanding of Planetary Systems through Population-Level, Large-Scale Surveys

Over the past three decades, exoplanet research has delivered an extensive census of planets spanning a wide range of masses, sizes, and orbital configurations. Despite this progress, the physical interpretation of these populations remains severely limited, as precise constraints on planetary masses, interior structures, and atmospheres are available only for a small, highly selected subset of targets. As a result, most known exoplanets remain physically ambiguous, preventing the construction of robust population-level trends and limiting our understanding of planet formation, evolution, and habitability. In the coming decades, missions such as PLATO, Earth 2.0, and the Nancy Grace Roman Space Telescope will dramatically expand the number of exoplanets detected. However, without a corresponding capability to characterise planetary masses and atmospheres at scale, these discoveries will remain largely detection-driven. Current and planned facilities, including JWST and ELT-class instruments, excel at detailed studies of individual systems but are intrinsically unsuited for large, homogeneous surveys. This white paper identifies population-level physical characterisation as a fundamental science challenge for the 2040s and motivates the need for a new observational paradigm. We outline how photonics-enabled, modular telescope architectures can deliver the survey speed, stability, and scalability required to jointly probe planetary interiors and atmospheres across statistically meaningful samples, thereby enabling a comprehensive and physically grounded understanding of planetary systems.

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arXiv2026

TOI-3862 b: A dense super-Neptune deep in the hot Neptune desert

The structure and evolution of close-in exoplanets are shaped by atmospheric loss and migration processes, which give rise to key population features such as the hot Neptune desert, ridge, and savanna - regions of the period-radius space whose boundaries offer critical insights into planetary formation and survival. As part of the KESPRINT collaboration, we selected the TESS transiting planet candidate TOI-3862.01 for radial velocity follow-up to confirm its planetary nature and characterize its mass and bulk properties. This planet candidate is of particular interest due to its position in the middle of the hot Neptune desert, making it a valuable probe for testing theories of planet migration and atmospheric loss. We confirmed the planetary nature and determined the mass of TOI-3862.01 (hereinafter TOI-3862b) by performing a joint fit with both transit and radial velocity data, precisely characterizing the bulk properties of this planet. TOI-3862b is a super-Neptune on a 1.56-day orbit around a Sun-like star with an effective temperature of 5300$\pm$50K. It has a mass of 53.7$_{-2.9}^{+2.8}$ M$_{\oplus}$ and a radius of 5.53$\pm$0.18 R$_{\oplus}$, corresponding to a density of 1.7$\pm$0.2 g/cm^3. This places it among the rare population of hot and dense super-Neptune desert planets. TOI-3862b, residing deep in the hot Neptune desert, represents a rare occurrence in an otherwise sparsely populated region, offering a valuable opportunity to probe the processes that may allow planets to survive in such environments.

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arXiv2025

Precise mass and radius determination for two new and one known Neptune-sized planets around G Dwarf hosts

As part of the KESPRINT collaboration, we present the discovery and characterization of three exoplanets in the sub-Neptune to super-Neptune regime, spanning key regions of the exo-Neptunian landscape. TOI-1472c and TOI-1648b are newly discovered sub-Neptunes, while TOI-1472b is a previously known super-Neptune for which we provide an improved mass measurement. These planets have orbital periods of 6--15 days and radii of 2.5--4.1 R$_\oplus$, probing regions where planet formation and atmospheric evolution remain poorly understood. We combine TESS transit photometry with ground-based radial velocities to determine precise masses, radii, and orbital properties. TOI-1472b has a mass of $18.0^{+0.84}_{-0.85}$ M$_\oplus$ and a radius of $4.06 \pm 0.10$ R$_\oplus$, TOI-1472c has a mass of $21.1^{+0.96}_{-0.99}$ M$_\oplus$ and a radius of $3.33 \pm 0.08$ R$_\oplus$, and TOI-1648b has a mass of $7.4^{+1.1}_{-1.3}$ M$_\oplus$ and a radius of $2.54^{+0.14}_{-0.12}$ R$_\oplus$. The planets exhibit a range of eccentricities (0.041--0.178), indicating diverse evolutionary histories. TOI-1648b, with a high Transmission Spectroscopy Metric (TSM $\sim$59), is a promising target for atmospheric characterization. Together, these three planets provide precise constraints on the structure, composition, and dynamical evolution of small to intermediate-sized exoplanets, enriching our understanding of the exo-Neptunian landscape.

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arXiv2025

The Atmospheric Composition of Sub-Neptune K2-18 b and Implications for its Formation

Unlocking the atmospheres of sub-Neptunes is among JWST's major achievements, yet such observations demand complex analyses that strongly affect interpretations. We present an independent reanalysis of the original JWST transmission spectrum of K2-18 b, to assess the robustness of previously claimed detections, explore the parameter space, and implications for its formation. The observations were reduced using a combination of public and customized pipelines producing a total of 12 different versions of the transmission spectrum by varying: spectral binning, limb-darkening, and a novel correction for the occulted stellar spot. We then performed atmospheric retrievals using TauREx 3, comparing models of varying complexity, robustly detecting CH$_4$ (3-4$\sigma$) across all configurations. The evidence for CO$_2$ is weaker and highly model-dependent. The tentative detection of dimethyl sulphide (DMS) vanishes in our most comprehensive retrieval models. We find that correcting the stellar spot in the NIRISS transit is a critical step, introducing a uniform offset that primarily drives the inference of a lower mean molecular weight atmosphere. Furthermore, the assumed complexity of the retrieval model itself introduces significant biases; including more molecules systematically increases the retrieved CH$_4$ abundance and atmospheric mean molecular weight, even for species without spectral features. The data are consistent with a hydrogen-rich atmosphere with an elevated O and an even more elevated C abundance, leading to a super-solar C/O. We show that the physical properties of the system planets K2-18 c, and K2-18 b are consistent with those expected by the in situ formation theory of Inside-Out Planet Formation (IOPF), interior to the carbon "soot" line, where an elevated C/O ratio of a primordial atmosphere is expected to be inherited from the protoplanetary disk.

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arXiv2025

Testing the performance of cross-correlation techniques to search for molecular features in JWST NIRSpec G395H observations of transiting exoplanets

Cross-correlations techniques offer an alternative method to search for molecular species in JWST observations of exoplanet atmospheres. In a previous article, we applied cross-correlation functions for the first time to JWST NIRSpec/G395H observations of exoplanet atmospheres, resulting in a detection of CO in the transmission spectrum of WASP-39b and a tentative detection of CO isotopologues. Here we present an improved version of our cross-correlation technique and an investigation into how efficient the technique is when searching for other molecules in JWST NIRSpec/G395H data. Our search results in the detection of more molecules via cross-correlations in the atmosphere of WASP-39b, including $\rm H_{2}O$ and $\rm CO_{2}$, and confirms the CO detection. This result proves that cross-correlations are a robust and computationally cheap alternative method to search for molecular species in transmission spectra observed with JWST. We also searched for other molecules ($\rm CH_{4}$, $\rm NH_{3}$, $\rm SO_{2}$, $\rm N_{2}O$, $\rm H_{2}S$, $\rm PH_{3}$, $\rm O_{3}$ and $\rm C_{2}H_{2}$) that were not detected, for which we provide the definition of their cross-correlation baselines for future searches of those molecules in other targets. We find that that the cross-correlation search of each molecule is more efficient over limited wavelength regions of the spectrum, where the signal for that molecule dominates over other molecules, than over broad wavelength ranges. In general we also find that Gaussian normalization is the most efficient normalization mode for the generation of the molecular templates.

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arXiv2025

On the synergetic use of Ariel and JWST for exoplanet atmospheric science

This paper explores the potential for strategic synergies between the JWST and the Ariel telescopes, two flagship observatories poised to revolutionise the study of exoplanet atmospheres. Both telescopes have the potential to address common fundamental questions about exoplanets-especially concerning their nature and origins-and serve a growing scientific community. With their operations now anticipated to overlap, starting from 2030, there is a unique opportunity to enhance the scientific outputs of both observatories through coordinated efforts. In this report, authored by the Ariel-JWST Synergy Working Group, part of the Ariel Consortium Science Team, we summarise the capabilities of JWST and Ariel; we highlight their key differences, similarities, synergies, and distinctive strengths. Ariel is designed to conduct a broad survey of exoplanet atmospheres but remains highly flexible, allowing the mission to integrate insights from JWST's discoveries. Findings from JWST, including data from initiatives shaped by NASA's decadal survey priorities and community-driven research themes, will inform the development of Ariel's core survey strategy. Conversely, Ariel's ability to perform broad-wavelength coverage observations for bright targets provides complementary avenues for exoplanet researchers, particularly those interested in time-domain observations and large-scale atmospheric studies. This paper identifies key pathways for fostering JWST-Ariel synergies, many of which can be initiated even before Ariel's launch. Leveraging their complementary designs and scopes, JWST and Ariel can jointly address fundamental questions about the nature, formation, and evolution of exoplanets. Such strategic collaboration has the potential to maximise the scientific returns of both observatories and lay the foundation for future facilities in the roadmap to exoplanet exploration.

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arXiv2025

TOI-1438: A rare system with two short-period sub-Neptunes and a tentative long-period Jupiter-like planet orbiting a K0V star

We present the detection and characterisation of the TOI-1438 multi-planet system discovered by TESS. We collected a series of follow-up observations including high-spectral resolution observations with HARPS-N over a period of five years. Our modelling shows that the K0V star hosts two transiting sub-Neptunes with Rb = 3.04 +/- 0.19 RE, Rc = 2.75 +/- 0.14 RE, Mb = 9.4 +/- 1.8 ME, and Mc = 10.6 +/- 2.1 ME. The orbital periods of planets b and c are 5.1 and 9.4 days, respectively, corresponding to instellations of 145 +/- 10 and 65 +/- 4 FE. The bulk densities are 1.8 +/- 0.5 and 2.9 +/- 0.7 g cm-3, respectively, suggesting a volatile-rich interior composition. We computed a set of planet interior structure models. Planet b presents a high-metallicity envelope that can accommodate up to 2.5 % in H/He in mass, while planet c cannot have more than 0.2 % as H/He in mass. For any composition of the core considered (Fe-rock or ice-rock), both planets would require a volatile-rich envelope. In addition to the two planets, the radial velocity (RV) data clearly reveal a third signal, likely coming from a non-transiting planet, with an orbital period of 7.6 +1.6 -2.4 years and a radial velocity semi-amplitude of 35+3-5 m s-1. Our best fit model finds a minimum mass of 2.1 +/- 0.3 MJ and an eccentricity of 0.25+0.08-0.11. However, several RV activity indicators also show strong signals at similar periods, suggesting this signal might (partly) originate from stellar activity. More data over a longer period of time are needed to conclusively determine the nature of this signal. If it is confirmed as a triple-planet system, TOI-1438 would be one of the few detected systems to date characterised by an architecture with two small, short-period planets and one massive, long-period planet, where the inner and outer systems are separated by an orbital period ratio of the order of a few hundred.

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arXiv2025

The mass of the exo-Venus Gliese 12 b, as revealed by HARPS-N, ESPRESSO, and CARMENES

Small temperate planets are prime targets for exoplanet studies due to their possible similarities with the rocky planets in the Solar System. M dwarfs are promising hosts since the planetary signals are within our current detection capabilities. Gliese 12 b is a Venus-sized temperate planet orbiting a quiet M dwarf. We present here the first precise mass measurement of this small exoplanet. We performed a detailed analysis using HARPS-N, ESPRESSO, and CARMENES radial velocities, along with new and archival \tess, \cheops, and MuSCAT2/3 photometry data. From fitting the available data, we find that the planet has a radius of $R_\mathrm{p} = 0.93\pm0.06 \,\mathrm{R_\oplus}$ and a mass of $M_\mathrm{p} = 0.95^{+0.29}_{-0.30} \,\mathrm{M_\oplus}$ (a $3.2\sigma$ measurement of the semi-amplitude $K=0.67\pm0.21\,\mathrm{m\,s^{-1}}$), and is on an orbit with a period of $12.761418^{+0.000060}_{-0.000055}\,\mathrm{d}$. A variety of techniques were utilised to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of $T_\mathrm{eq}=317 \pm 8\,\mathrm{K}$, assuming an albedo of zero, and a density consistent with that of Earth and Venus ($\rho_\mathrm{p}=6.4\pm2.4\,\mathrm{g\,cm^{-3}}$). We find that Gliese 12 b has a predominantly rocky interior and simulations indicate that it is unlikely to have retained any of its primordial gaseous envelope. The bulk properties of Gliese 12 b place it in an extremely sparsely populated region of both mass--radius and density--$T_\mathrm{eq}$ parameter space, making it a prime target for follow-up observations, including Lyman-$\alpha$ studies.

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arXiv2024

JWST/NIRISS and HST: Exploring the improved ability to characterise exoplanet atmospheres in the JWST era

The Hubble Space Telescope has been a pioneering instrument for studying the atmospheres of exoplanets, specifically its WFC3 and STIS instruments. With the launch of JWST, we are able to observe larger spectral ranges at higher precision. NIRISS/SOSS covers the range 0.6--2.8 microns, and thus can serve as a direct comparison to WFC3 (0.8--1.7 microns). We perform atmospheric retrievals of WFC3 and NIRISS transmission spectra of WASP-39 b in order to compare their constraining power. We find that NIRISS is able to retrieve precise H2O abundances that do not suffer a degeneracy with the continuum level, due to the coverage of multiple spectral features. We also combine these datasets with spectra from STIS, and find that challenges associated with fitting the steep optical slope can bias the retrieval results. In an effort to diagnose the differences between the WFC3 and NIRISS retrievals, we perform the analysis again on the NIRISS data cut to the same wavelength range as WFC3. We find that the water abundance is in strong disagreement with both the WFC3 and full NIRISS retrievals, highlighting the importance of wide wavelength coverage. Finally, we carry out mock retrievals on the different instruments, which shows further evidence of the challenges in constraining water abundance from the WFC3 data alone. Our study demonstrates the vast information gain of JWST's NIRISS instrument over WFC3, highlighting the insights to be obtained from our new era of space-based instruments.

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arXiv2024

Low abundances of TiO and VO on the Dayside of KELT-9 b: Insights from Ground-Based Photometric Observations

We present ground-based photometric observations of secondary eclipses of the hottest known planet KELT-9b using MuSCAT2 and Sinistro. We detect secondary eclipse signals in $i$ and $z_{\rm s}$ with eclipse depths of $373^{+74}_{-75}$ ppm and $638^{+199}_{-178}$, respectively. We perform an atmospheric retrieval on the emission spectrum combined with the data from HST/WFC3, Spitzer, TESS, and CHEOPS to obtain the temperature profile and chemical abundances, including TiO and VO, which have been thought to produce temperature inversion structures in the dayside of ultra-hot Jupiters. While we confirm a strong temperature inversion structure, we find low abundances of TiO and VO with mixing ratios of $\rm{log(TiO)}=-7.80^{+0.15}_{-0.30}$ and $\rm{log(VO)}=-9.60^{+0.64}_{-0.57}$, respectively. The low abundances of TiO and VO are consistent with theoretical predictions for such an ultra-hot atmosphere. In such low abundances, TiO and VO have little effect on the temperature structure of the atmosphere. The abundance of ${\rm e}^{-}$, which serves as a proxy for ${\rm H}^{-}$ ions in this study, is found to be high, with $\rm{log(e^-)}=-4.89\pm{0.06}$. These results indicate that the temperature inversion in KELT-9 b's dayside atmosphere is likely not caused by TiO/VO, but rather by the significant abundance of ${\rm H}^{-}$ ions. The best-fit model cannot fully explain the observed spectrum, and chemical species not included in the retrieval may introduce modeling biases. Future observations with broader wavelength coverage and higher spectral resolution are expected to provide more accurate diagnostics on the presence and abundances of TiO/VO. These advanced observations will overcome the limitations of current data from HST and photometric facilities, which are constrained by narrow wavelength coverage and instrumental systematics.

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arXiv2024

TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by TTVs

We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2-day orbit located interior to a previously known hot Jupiter, TOI-1408 b ($P=4.42$ d, $M=1.86\pm0.02\,M_\mathrm{Jup}$, $R=2.4\pm0.5\,R_\mathrm{Jup}$) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations (TDVs) for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet's orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite (TESS) and ground-based facilities leads to an inner planet radius of $2.22\pm0.06\,R_\oplus$ and mass of $7.6\pm0.2\,M_\oplus$ that locates the planet into the Sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.

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arXiv2024

Sulphur dioxide in the mid-infrared transmission spectrum of WASP-39b

The recent inference of sulphur dioxide (SO$_2$) in the atmosphere of the hot ($\sim$1100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations suggests that photochemistry is a key process in high temperature exoplanet atmospheres. This is due to the low ($<$1 ppb) abundance of SO$_2$ under thermochemical equilibrium, compared to that produced from the photochemistry of H$_2$O and H$_2$S (1-10 ppm). However, the SO$_2$ inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 $\mu$m, and therefore the detection of other SO$_2$ absorption bands at different wavelengths is needed to better constrain the SO$_2$ abundance. Here we report the detection of SO$_2$ spectral features at 7.7 and 8.5 $\mu$m in the 5-12 $\mu$m transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS). Our observations suggest an abundance of SO$_2$ of 0.5-25 ppm (1$\sigma$ range), consistent with previous findings. In addition to SO$_2$, we find broad water vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 $\mu$m. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy element content (metallicity) for WASP-39b of $\sim$7.1-8.0 $\times$ solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.

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arXiv2024

Debris Disks can Contaminate Mid-Infrared Exoplanet Spectra: Evidence for a Circumstellar Debris Disk around Exoplanet Host WASP-39

The signal from a transiting planet can be diluted by astrophysical contamination. In the case of circumstellar debris disks, this contamination could start in the mid-infrared and vary as a function of wavelength, which would then change the observed transmission spectrum for any planet in the system. The MIRI/LRS WASP-39b transmission spectrum shows an unexplained dip starting at $\sim$10 $μ$m that could be caused by astrophysical contamination. The spectral energy distribution displays excess flux at similar levels to that which are needed to create the dip in the transmission spectrum. In this article, we show that this dip is consistent with the presence of a bright circumstellar debris disk, at a distance of $>$2 au. We discuss how a circumstellar debris disk like that could affect the atmosphere of WASP-39b. We also show that even faint debris disks can be a source of contamination in MIRI exoplanet spectra.

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arXiv2024

Two-Dimensional Eclipse Mapping of the Hot Jupiter WASP-43b with JWST MIRI/LRS

We present eclipse maps of the two-dimensional thermal emission from the dayside of the hot Jupiter WASP-43b, derived from an observation of a phase curve with the JWST MIRI/LRS instrument. The observed eclipse shapes deviate significantly from those expected for a planet emitting uniformly over its surface. We fit a map to this deviation, constructed from spherical harmonics up to order $\ell_{\rm max}=2$, alongside the planetary, orbital, stellar, and systematic parameters. This yields a map with a meridionally-averaged eastward hot-spot shift of $(7.75 \pm 0.36)^{\circ}$, with no significant degeneracy between the map and the additional parameters. We show the latitudinal and longitudinal contributions of the day-side emission structure to the eclipse shape, finding a latitudinal signal of $\sim$200 ppm and a longitudinal signal of $\sim$250 ppm. To investigate the sensitivity of the map to the method, we fix the non-mapping parameters and derive an "eigenmap" fitted with an optimised number of orthogonal phase curves, which yields a similar map to the $\ell_{\rm max}=2$ map. We also fit a map up to $\ell_{\rm max}=3$, which shows a smaller hot-spot shift, with a larger uncertainty. These maps are similar to those produced by atmospheric simulations. We conclude that there is a significant mapping signal which constrains the spherical harmonic components of our model up to $\ell_{\rm max}=2$. Alternative mapping models may derive different structures with smaller-scale features; we suggest that further observations of WASP-43b and other planets will drive the development of more robust methods and more accurate maps.

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arXiv2024

Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications

The goal of this white paper is to provide a snapshot of the data availability and data needs primarily for the Ariel space mission, but also for related atmospheric studies of exoplanets and brown dwarfs. It covers the following data-related topics: molecular and atomic line lists, line profiles, computed cross-sections and opacities, collision-induced absorption and other continuum data, optical properties of aerosols and surfaces, atmospheric chemistry, UV photodissociation and photoabsorption cross-sections, and standards in the description and format of such data. These data aspects are discussed by addressing the following questions for each topic, based on the experience of the "data-provider" and "data-user" communities: (1) what are the types and sources of currently available data, (2) what work is currently in progress, and (3) what are the current and anticipated data needs. We present a GitHub platform for Ariel-related data, with the goal to provide a go-to place for both data-users and data-providers, for the users to make requests for their data needs and for the data-providers to link to their available data. Our aim throughout the paper is to provide practical information on existing sources of data whether in databases, theoretical, or literature sources.

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arXiv2024

Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b

Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5-12 $μ$m with JWST's Mid-Infrared Instrument (MIRI). The spectra reveal a large day-night temperature contrast (with average brightness temperatures of 1524$\pm$35 and 863$\pm$23 Kelvin, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase curve shape and emission spectra strongly suggest the presence of nightside clouds which become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2$σ$ upper limit of 1-6 parts per million, depending on model assumptions).

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