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Rocky (exo)planets can be classified based on their mantle viscous state. The mantle viscosity influences the efficiency of convection and heat loss of the planet, altering the outgassing rate. Low viscous planets are hypothesized to have strong volcanic activity reshaping the surface and changing the atmosphere. This can be seen in other almost-similar rocky bodies such as Io, one of Jupiter’s Galilean moons, and would be expected of young rocky exoplanets. Whereas, the intermediate viscous planets have less vigorous resurfacing. They experience occasional complete mantle-overturn to slow-moving plate tectonics driven by mantle convection. As a result, their atmospheres vary little or smoothly across time. High viscous planets can be seen as inert, with little or no mantle convection. Moreover, hotspot volcanism might still occasionally contribute to outgassing, producing a less dominant atmosphere. Through this relationship, a planet’s atmosphere could reveal information about the evolution of a planet's interior and surface. However, we rely on primary observables to characterize (exo)planets. So, is there a correlation between a planet's orbital position and mantle viscosity? The answer to this question would aid in the characterization of rocky exoplanets, which is the focus of this work. To study the relationship between a planet’s mantle viscous state, interior composition, and structure. We use Perple-X to generate mineral physics properties, and Burnman to build a 1-dimensional depth profile of the planet. From this, 2-dimensional annulus compressible convection models are developed using ASPECT. And, exploring the stagnant lid, the episodic lid, and the tectonic convection regimes. We consider the anelastic liquid approximation (ALA), and the truncated anelastic liquid approximation (TALA) formulations. An isoviscous profile results in a hot mantle but can be used for first-order approximations of mantle dynamics without a crust. However, the presence of crust requires for temperature-dependent stratified viscosity profile for the deeper mantle to allow for the cooling of the mantle. The stratification structure of the mantle is determined by the temperature sensitivity of the mineral phases present in the depth profile of the mantle. The iron mass fraction of the planet, which is highly dependent on the orbital position dictates the thermal state of the given planet. Moreover, a high mass iron fraction in the mantle results in a highly viscous planet. Which cools much faster but with a higher average temperature in the earlier phases of evolution. And vice versa to a similar mantle state with less iron mass fraction in the mantle.

Ground-based spectrophotometric observations of transiting exoplanet atmospheres conventionally rely on correcting for instrumental and telluric systematics in the light curves by using reference stars that are simultaneously observed. However, this approach often leads to sub-optimal corrections due to multiple accounts on which the target and reference star spectra can be affected by systematics differently through the night, ultimately limiting the achievable precision and accuracy on the measurement of planetary atmospheric signatures. We introduce a new method based on Gaussian Processes regression to address this challenge by extracting the transmission or emission spectrum without relying explicitly on the reference stars. Our new method overcomes the necessity of using reference stars and opens up the doors to ground-based atmospheric observations of exoplanets orbiting bright host stars (e.g. those discovered by TESS) that intrinsically lack proper reference stars. We present results from the application of our method to a broad sample of exoplanets observed in the optical and near-infrared using Gemini/GMOS and Keck/MOSFIRE. We also discuss the challenges and possible solutions arising from stellar variability towards combining high precision ground-based low-resolution spectroscopy observations in complementarity with future infrared observations from HST and JWST.

The interpretation of general trends in exoplanet atmospheres is challenging because they exhibit a wide range of diverse properties in terms of composition, structure, and overall atmospheric physics. In this context exoplanet’s in extreme regimes can help to understand global planetary properties. In this project, we focus on a few exoplanets that are outliers in their atmospheric properties and discuss what we can learn about the overall population of hot-jupiters from these peculiar objects. We present studies of exo-atmospheric processes in extreme regimes of temperature, of entropy, of radiative and advective timescales, and of formation stages. This project combines these various physical properties in a unique and innovative manner to understand the most crucial properties of hot-Jupiters. Practically, we leverage the unique capabilities of Hubble Space Telescope Wide Field Camera 3 together with novel data analysis techniques to understand the nature of a set of exoplanets that reside under these extreme conditions. Ultimately, this project enable us to improve our understanding of exo-atmospheric processes and planet formation that ultimately shape the atmospheres of hot Jupiters that are observed today.

The composition of a planet atmosphere is heavily influenced by the planet formation process and subsequent evolution. In this context, planet formation models can provide us with vital information on how different assumptions and conditions would affect the planet compositions. The combination of these models with atmospheric models are then very strong tools to help us interpret observations and connect atmospheric traits to the planet formation model. In this work, we developed a framework that uses models for protoplanetary disks and planet formation that parametrizes the inputs in simple manners and forms giant planets with their atmospheres. Using this framework, we simulate a large population of planets with the same final planet mass and orbit distance, with different initial forming conditions. This allows us to study the trends that explain how the formation process affects the composition of giant planets. Our simulation allows us to study the effects of migration and in situ formation on the planet composition. Figure (1) shows a hundred thousand planets with one Jupiter mass at a distance of 0.02 AU. Each point on these plots represents a different initial condition. Top right plot shows the influence of the amount of dust grains, solids with a stokes number less than one, on the metallicity and the C/O ratio. Top left plot shows the influence of planetesimals, solids with a stokes number much higher than one, on the metallicity and C/O ratio. Th bottom plot shows the influence of the initial orbital distance on the C/O ratio and the metallicity of the planet. This plot shows that the solid size distribution in the disk has an important role in causing the planet metallicity and C/O ratio changes between sub-solar and super solar. Planets that are formed in disks where the majority of the solids has a stokes number lower than 1, will end up with a more solar or sub-solar metallicity and solar to super-solar C/O ratio. On the other hand, planets that are formed in disks where the majority of the solid has a stocks number much higher than one, will end up with a more super-solar metallicity and sub-solar C/O ratio. In addition we show that the C/O ratio together with the metallicity of the planets with super-solar metallicity, can put a lower limit on the initial orbit where the planet initiates migration type II. In order to study planets with solar and sub-solar metallicity, we suggest that it is important to look at atomic ratios such as S/N, Si/N, Fe/N, or Mg/N. To have a comprehensive understanding of the connection between disk and planet atmospheres, we couple our model describe above to an atmospheric retrieval model. We retrieve the formation parameters that we introduce in our formation model from the observed spectra for different planets. We then look at how planet characteristics, such as its mass, radius, orbital distance, and atmospheric condition affect the possibility of retrieving their formation history. Our formation model in combination with atmospheric models, provides a strong tool in combination with space missions such as ARIEL and JWST. In particular, with JWST we can obtain information about the building blocks of exoplanet atmospheres from observing the planets themselves and the disks in which they are formed and compare them to our model predictions in order to constrain planet formation scenarios from their atmospheric composition. Additionally, our model can be used to inform the target list for ARIEL as it predicts for which planets it is more likely to retrieve information about their formation history.

We are presenting the first atmospheric study of a young transiting exoplanet. We focus on the V1298 Tau system, which contains 4 giant transiting planets that orbit the young (23Myr) T Tauri star V1298 Tau. We have observed one primary transit of planet V1298 Tau b with HST to learn about its atmospheric properties. This planet is ideally suited for atmospheric studies using transmission spectroscopy since it is a warm gas giant (Teq=677 K) with a very large atmospheric scale height (~250 km).From theoretical models we expect strong water absorption features in its transmission spectra. However, this planet is particularly interesting since it is expected to be undergoing atmospheric 'erosion' due to high XUV flux from its host star and its internal heat of formation, and show how our observations can constrained the escape rate. The V1298 Tau system is also interesting for the study of comparative exoplanetology between four freshly formed planets as their atmospheres are expected to carry fossil signatures of the planetary disk from which they formed. As a follow-up of the HST observations, we are scheduling observations planets b and c with JWST+NIRSpec in transmission as part of a GO-1 accepted proposal. V1298 Tau is an active star and we find signatures of bright spots and flares on the stellar surface with the HST+WFC3 observations, and emphasise the challenges that the stellar activity poses for such system. In this poster, we present results from the current programs and highlight the scientific interests of this system.

Ultra-hot Jupiters (Teq ≥ 2,500 K) are the hottest gaseous giants known. They emerged as ideal laboratories to test theories of atmospheric structure and its link to planet formation. Indeed, because of their high temperatures, (1) they likely host atmospheres in chemical equilibrium and (2) clouds do not form in their day-side. Thousands of lines of refractory elements such as iron, normally inaccessible in planets, can be studied through high spectral resolution emission spectroscopy, providing a first look into the chemistry of refractory elements in exoplanets. In this talk we report the detection of neutral iron in the day-side emission spectrum of KELT-9b (Tday ~ 4,000 K), the first detection of an atomic species in the emission spectrum of an exoplanet, obtained with HARPS-N optical data gathered in the framework of the GAPS collaboration. Our detection unambiguously indicates the presence of a thermal inversion in the atmosphere of the planet. We also present a new technique to extract planetary parameters from the cross-correlation function in a statistically sound framework, which makes possible the combination with information from the planetary continuum that can be obtained with complementary space facilities. This is a crucial step towards the measurement of metal abundances in exoplanets, a quantity that can be compared to predictions of planet formation theories. In the near future, our technique will be extended to cooler exoplanets. In the era of EELTs and JWST, this kind of measurements could ultimately open a new window on exoplanet formation and evolution.

We present a comparative exoplanetology program of a broad sample of transiting gas giant exoplanet atmospheres using a multi-wavelength ground-based survey. The survey comprises optical and near-infrared spectrophotometric observations with Gemini/GMOS and Keck/MOSFIRE respectively. By observing transits and eclipses of an ensemble of close-in gas giants spanning a range of varying bulk and stellar host properties, and using a consistent methodology for modeling systematics and stellar activity, we put constraints on the presence and properties of clouds, alkali metals, and molecular absorbers in their atmospheres. Combining these results with observations from other observatories (TESS, HST, and Spitzer), we probe the overall properties of close-in giant exoplanet atmospheres, including their metallicity, using multiple tracers across the wide wavelength range. Characterizing the bulk chemical and physical properties of the whole sample helps to constrain the formation and evolution histories of these planets. We also discuss the opportunities of low-resolution spectroscopy observations of exoplanet atmospheres in the JWST era.