Observations of exoplanet atmospheres in high resolution have the potential to resolve individual planetary absorption lines, despite the issues associated with ground-based observations. The removal of contaminating stellar and telluric absorption features is one of the most sensitive steps required to reveal the planetary spectrum and, while many different detrending methods exist, it remains difficult to directly compare the performance and efficacy of these methods. Additionally, though the standard cross-correlation method enables robust detection of specific atmospheric species, it only probes for features that are expected a priori. Here we present a novel methodology using Gaussian process (GP) regression to directly model the components of high-resolution spectra, which partially addresses these issues. We use two archival CRIRES/VLT data sets as test cases, observations of the hot Jupiters HD 189733 b and 51 Pegasi b, recovering injected signals with average line contrast ratios of $\sim 4.37 \times 10^{-3}$ and $\sim 1.39 \times 10^{-3}$, and planet radial velocities $ΔK_\mathrm{p} =1.45 \pm 1.53\,\mathrm{km\,s^{-1}}$ and $ΔK_\mathrm{p}=0.12\pm0.12\,\mathrm{km\,s^{-1}}$ from the injection velocities respectively. In addition, we demonstrate an application of the GP method to assess the impact of the detrending process on the planetary spectrum, by implementing injection-recovery tests. We show that standard detrending methods used in the literature negatively affect the amplitudes of absorption features in particular, which has the potential to render retrieval analyses inaccurate. Finally, we discuss possible limiting factors for the non-detections using this method, likely to be remedied by higher signal-to-noise data.
Aims: ARCiS, a novel code for the analysis of exoplanet transmission and emission spectra is presented. The aim of the modelling framework is to provide a tool able to link observations to physical models of exoplanet atmospheres. Methods: The modelling philosophy chosen in this paper is to use physical and chemical models to constrain certain parameters while keeping free the parts where our physical understanding is still more limited. This approach, in between full physical modelling and full parameterisation, allows us to use the processes we understand well and parameterise those less und…
We present a fast and user friendly exoplanet transit light curve modelling package PyTransit, implementing optimised versions of the Gimenéz and the Mandel & Agol transit models. The package offers an object-oriented Python interface to access the two models implemented natively in Fortran with OpenMP parallelisation. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PyTransit is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of datapoints, and of multi-pass…
[Abridged] This review paper discussed which chemical effects may be at play in a planet-forming disk midplane, which effects are relevant under different conditions, and which tools are available for modelling chemical kinetics in a disk midplane. The review goes on to discuss some important efforts in the planet formation modelling community to treat chemical evolution, and, vice versa, efforts in the chemical modelling community to implement more physical effects related to planet formation into the chemical modelling. The aim of this review is both to outline some concepts related to plane…
Eleven transit light curves for the exoplanet WASP-140b were studied with the primary objective to investigate the possibility of transit timing variations (TTVs). Previously unstudied MicroObservatory and Las Cumbres Global Telescope Network photometry were analysed using Markov Chain Monte Carlo techniques, including new observations collected by this study of a transit in December 2021. No evidence was found for TTVs. We used two transit models coupled with Bayesian optimization to explore the physical parameters of the system. The radius for WASP-140b was estimated to be $1.38^{+0.18}_{-0.…
A significant fraction of an exoplanet transit model evaluation time is spent calculating projected distances between the planet and its host star. This is a relatively fast operation for a circular orbit, but slower for an eccentric one. However, because the planet's position and its time derivatives are constant for any specific point in orbital phase, the projected distance can be calculated rapidly and accurately in the vicinity of the transit by expanding the planet's $x$ and $y$ positions in the sky plane into a Taylor series at mid-transit. Calculating the projected distance for an elli…
Program SHELLSPEC is designed to calculate light curves, spectra, and images of interacting binaries and extra-solar planets immersed in a moving gaseous or dusty circumstellar matter. It solves simple radiative transfer along the line of sight in 3D moving media. The Roche model and synthetic spectra from the stellar atmosphere models such as TLUSTY from Ivan Hubeny can be used as a boundary condition for the radiative transfer. The latest publicly available version is Shellspec39. The code has been combined with other methods such as Doppler tomography and interferometry and used to analyze …
The physical characteristics and atmospheric chemical composition of newly discovered exoplanets are often inferred from their transit spectra which are obtained from complex numerical models of radiative transfer. Alternatively, simple analytical expressions provide insightful physical intuition into the relevant atmospheric processes. The deep learning revolution has opened the door for deriving such analytical results directly with a computer algorithm fitting to the data. As a proof of concept, we successfully demonstrate the use of symbolic regression on synthetic data for the transit rad…
High-contrast imaging (HCI) is one of the most challenging techniques for exoplanet detection. It relies on sophisticated data processing to reach high contrasts at small angular separations. Most data processing techniques of this type are based on the angular differential imaging (ADI) observing strategy to perform the reference PSF subtraction, and generally make use of signal-to-noise (S/N) maps to infer the existence of planetary signals via thresholding. An alternative method for generating the final detection map was recently proposed with the regime-switching model (RSM) map, which use…
The two most successful methods for exoplanet detection rely on the detection of planetary signals in photometric and radial velocity time-series. This depends on numerical techniques that exploit the synergy between data and theory to estimate planetary, orbital, and/or stellar parameters. In this work, we present a new version of the exoplanet modelling code pyaneti. This new release has a special emphasis on the modelling of stellar signals in radial velocity time-series. The code has a built-in multidimensional Gaussian process approach to modelling radial velocity and activity indicator t…
The spectrum of an exoplanet reveals the physical, chemical, and biological processes that have shaped its history and govern its future. However, observations of exoplanet spectra are complicated by the overwhelming glare of their host stars. This review chapter focuses on high resolution spectroscopy (HRS; R=25,000-100,000), which helps to disentangle and isolate the exoplanet's spectrum. At high spectral resolution, molecular features are resolved into a dense forest of individual lines in a pattern that is unique for a given molecule. For close-in planets, the spectral lines undergo large …
Spectral retrieval techniques are currently our best tool to interpret the observed exoplanet atmospheric data. Said techniques retrieve the optimal atmospheric components and parameters by identifying the best fit to an observed transmission/emission spectrum. Over the past decade, our understanding of remote worlds in our galaxy has flourished thanks to the use of increasingly sophisticated spectral retrieval techniques and the collective effort of the community working on exoplanet atmospheric models. A new generation of instruments in space and from the ground is expected to deliver higher…
In favourable conditions, the density of transiting planets in multiple systems can be determined from photometry data alone. Dynamical information can be extracted from light curves, providing modelling is done self-consistently, i.e. using a photodynamical model, which simulates the individual photometric observations instead of the more generally used transit times. We apply this methodology to the Kepler-138 planetary system. The derived planetary bulk densities are a factor of 2 more precise than previous determinations, and we find a discrepancy in the stellar bulk density with respect t…
New-generation spectrographs dedicated to the study of exoplanetary atmospheres require a high accuracy in the atmospheric models to better interpret the input spectra. Thanks to space missions, the observed spectra will cover a large wavelength range from visible to mid-infrared with an higher precision compared to the old-generation instrumentation, revealing complex features coming from different regions of the atmosphere. For hot and ultra hot Jupiters (HJs and UHJs), the main source of complexity in the spectra comes from thermal and chemical differences between the day and the night side…
It is the most appropriate time to characterize the Earth-like exoplanets in order to detect biosignature beyond the Earth because such exoplanets will be the prime targets of big-budget missions like JWST, Roman Space Telescope, HabEx, LUVOIR, TMT, ELT, etc. We provide models for the transmission spectra of the Earth-like exoplanets by incorporating effects of multiple scattering. For this purpose we numerically solve the full multiple-scattering radiative transfer equations instead of using Beer-Bouguer-Lambert's law that doesn't include the diffuse radiation due to scattering. Our models de…
We report twelve new transit observations of the exoplanet WASP-4b from the Transit Monitoring in the South Project (TraMoS) project. These transits are combined with all previously published transit data for this planet to provide an improved radius measurement of Rp = 1.395 +- 0.022 Rjup and improved transit ephemerides. In a new homogeneous analysis in search for Transit Timing Variations (TTVs) we find no evidence of those with RMS amplitudes larger than 20 seconds over a 4-year time span. This lack of TTVs rules out the presence of additional planets in the system with masses larger than …
Evaporating rocky exoplanets, such as KIC 12557548b, eject large amounts of dust grains, which can trail the planet in a comet-like tail. When such objects occult their host star, the resulting transit signal contains information about the dust in the tail. We aim to use the detailed shape of the Kepler light curve of KIC 12557548b to constrain the size and composition of the dust grains that make up the tail, as well as the mass loss rate of the planet. Using a self-consistent numerical model of the dust dynamics and sublimation, we calculate the shape of the tail by following dust grains fro…
Atmospheric retrievals of exoplanet transmission spectra allow constraints on the composition and structure of the day-night terminator region. Such retrievals in the past have typically assumed one-dimensional temperature structures which were adequate to explain extant observations. However, the increasing data quality expected from exoplanet spectroscopy with JWST motivates considerations of multidimensional atmospheric retrievals. We present AURA-3D, a three-dimensional atmospheric retrieval framework for exoplanet transmission spectra. AURA-3D includes a forward model that enables rapid c…
Exoplanet interior modelling usually makes the assumption that the elemental abundances of a planet are identical to those of its host star. Host stellar abundances are good proxies of planetary abundances, but only for refractory elements. This is particularly true for terrestrial planets, as evidenced by the relative differences in bulk chemical composition between the Sun and the Earth and other inner solar system bodies. The elemental abundances of a planet host star must therefore be devolatilised in order to correctly represent the bulk chemical composition of its terrestrial planets. Fu…
In anticipation of future flagship missions focused on the goal of achieving direct imaging of rocky exoplanets, we have developed a database of models to help the community examine the potential spectral characteristics of a broad range of rocky planet atmospheres. Using the publicly available Planetary Spectrum Generator (PSG), we have computed a grid of 141,600 rocky exoplanet geometric albedo spectra across a 7-dimensional parameter space. Using this grid, we have performed a color-color analysis seeking to identify the most useful near-ultraviolet and red or near-infrared photometric foll…
Stellar flares present challenges to the potential habitability of terrestrial planets orbiting M dwarf stars through inducing changes in the atmospheric composition and irradiating the planet's surface in large amounts of ultraviolet light. To examine their impact, we have coupled a general circulation model with a photochemical kinetics scheme to examine the response and changes of an Earth-like atmosphere to stellar flares and coronal mass ejections. We find that stellar flares increase the amount of ozone in the atmosphere by a factor of 20 compared to a quiescent star. We find that corona…
Modelling the Milky Way's exoplanet population based on cosmological galaxy simulations
Universitat de Barcelona (UB)（巴塞罗那大学）；Reial Acadèmia de Ciències i Arts de Barcelona（巴塞罗那皇家科学与艺术学院）；Shanghai Jiao Tong University（上海交通大学）；Observatori Fabra（法布拉天文台）；Observatório Nacional, MCTI（巴西国家天文台）
First generation optical coronagraphic telescopes will obtain images of cool gas and ice giant exoplanets around nearby stars. The albedo spectra of exoplanets at planet-star separations larger than about 1 AU are dominated by reflected light to beyond 1 μm and are punctuated by molecular absorption features. We consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 μm. We model Jupiter analogs with 1x and 3x the solar abundance of heavy elements, and Neptune analogs wit…
The analysis of the wavelength-dependent albedo of exoplanets represents a direct way to provide insight of their atmospheric composition and to constrain theoretical planetary atmosphere modelling. Wavelength-dependent albedo can be inferred from the exoplanet's reflected light of the host star, but this is not a trivial task. In fact, the planetary signal may be several orders of magnitude lower ($10^{-4}$ or below) than the flux of the host star, thus making its extraction very challenging. Successful detection of the planetary signature of 51~Peg\,b has been recently obtained by using cros…
Transmission spectroscopy is one of the premier methods used to probe the temperature, composition, and cloud properties of exoplanet atmospheres. Recent studies have demonstrated that the multidimensional nature of exoplanet atmospheres -- due to non-uniformities across the day-night transition and between the morning and evening terminators -- can strongly influence transmission spectra. However, the computational demands of 3D radiative transfer techniques have precluded their usage within atmospheric retrievals. Here we introduce TRIDENT, a new 3D radiative transfer model which rapidly com…
Observational studies of exoplanets are suggestive of a ubiquitous presence of clouds. The current modelling techniques used in emission to account for the clouds tend to require prior knowledge of the cloud condensing species and often do not consider the scattering effects of the cloud. We explore the effects that thermal scattering has on the emission spectra by modelling a suite of hot Jupiter atmospheres with varying cloud single-scattering albedos (SSAs) and temperature profiles. We examine cases ranging from simple isothermal conditions to more complex structures and physically driven c…
Simulations of exoplanet albedo profiles are key to planning and interpreting future direct imaging observations. In this paper we demonstrate the use of the Planetary Spectrum Generator to produce simulations of reflected light exoplanet spectra. We use PSG to examine multiple issues relevant to all models of directly imaged exoplanet spectra and to produce sample spectra of the bright, nearby exoplanet $\upsilon$ Andromedae d, a potential direct imaging target for next-generation facilities. We introduce a new, fast, and accurate subsampling technique that enables calculations of disk-integr…
The advent of space-based photometry missions such as CoRoT, Kepler and TESS has sparkled the development of asteroseismology and exoplanetology. The advent of PLATO will further strengthen such multi-disciplinary studies. Testing asteroseismic modelling and its importance for our understanding of planetary systems is crucial. We carried out a detailed modelling of Kepler-93, an exoplanet host star observed by Kepler. This star is particularly interesting as it is very similar to the PLATO benchmark target (G spectral type, ~ 6000K, ~ 1 Msun and ~ 1 Rsun) and provides a real-life testbed for p…
Lightning is an important electrical phenomenon, known to exist in several Solar System planets. It carries information on convection and cloud formation, and may be important for pre-biotic chemistry. Exoplanets and brown dwarfs have been shown to host environments appropriate for the initiation of lightning discharges. In this PhD project, I aim to determine if lightning on exoplanets and brown dwarfs can be more energetic than it is known from Solar System planets, what are the most promising signatures to look for, and if these "exo-lightning" signatures can be detected from Earth. This th…
We extend a data-based model-free multifractal method of exoplanet detection to probe exoplanetary atmospheres. Whereas the transmission spectrum is studied during the primary eclipse, we analyze the emission spectrum during the secondary eclipse, thereby probing the atmospheric limb. In addition to the spectral structure of exoplanet atmospheres, the approach provides information to study phenomena such as atmospheric flows, tidal-locking behavior, and the dayside-nightside redistribution of energy. The approach is demonstrated using Spitzer data for exoplanet HD189733b. The central advantage…
The occurrence of a planet transiting in front of its host star offers the opportunity to observe the planet's atmosphere filtering starlight. The fraction of occulted stellar flux is roughly proportional to the optically thick area of the planet, the extent of which depends on the opacity of the planet's gaseous envelope at the observed wavelengths. Chemical species, haze, and clouds are now routinely detected in exoplanet atmospheres through rather small features in transmission spectra, i.e., collections of planet-to-star area ratios across multiple spectral bins and/or photometric bands. T…
The K2-33 planetary system hosts one transiting ~5 R_E planet orbiting the young M-type host star. The planet's mass is still unknown, with an estimated upper limit of 5.4 M_J. The extreme youth of the system (<20 Myr) gives the unprecedented opportunity to study the earliest phases of planetary evolution, at a stage when the planet is exposed to an extremely high level of high-energy radiation emitted by the host star. We perform a series of 1D hydrodynamic simulations of the planet's upper atmosphere considering a range of possible planetary masses, from 2 to 40 M_E, and equilibrium temperat…
The recovery of an exoplanet's atmospheric parameters from its spectrum requires accurate knowledge of the spectral errors and covariances. Unfortunately, the complex image processing used in high-contrast integral-field spectrograph (IFS) observations generally produces spectral covariances that are poorly understood and often ignored. In this work, we show how to measure the spectral errors and covariances and include them self-consistently in parameter retrievals. By combining model exoplanet spectra with a realistic noise model generated from GPI early science data, we show that ignoring s…
We propose a method for observing transiting exoplanets with near-infrared high-resolution spectrometers. We aim to create a robust data analysis method for recovering atmospheric transmission spectra from transiting exoplanets over a wide wavelength range in the near infrared. By using an inverse method approach, combined with stellar models and telluric transmission spectra, the method recovers the transiting exoplanet's atmospheric transmittance at high precision over a wide wavelength range. We describe our method and have tested it by simulating observations. This method is capable of rec…
In order to recognize a habitable exoplanet from future observed spectra, we present new model reflected spectra and geometric albedo for modern and prebiotic (3.9 Ga) Earth-like exoplanets orbiting within the habitable zone of stars of spectral types F, G, K and M. We compute this for various atmospheric and surface compositions of the planets. Molecules that are potential biosignatures and act as greenhouse agents are incorporated in our model atmosphere. Various combinations of solid and liquid materials such as ocean, coast, land consisting of trees, grass, sand or rocks determine the surf…
New generation exoplanet imagers on large ground-based telescopes are highly optimised for the detection of young giant exoplanets in the near-infrared, but they are intrinsically limited for their characterisation by the low spectral resolution of their integral field spectrographs ($R<100$). High-dispersion spectroscopy at $R \gg 10^4$ would be a powerful tool for the characterisation of these planets, but there is currently no high-resolution spectrograph with extreme adaptive optics and coronagraphy that would enable such characterisation. With project HiRISE we propose to use fiber coupli…
Pandora is a SmallSat mission designed to study the atmospheres of exoplanets, and was selected as part of NASA's Astrophysics Pioneers Program. Transmission spectroscopy of transiting exoplanets provides our best opportunity to identify the makeup of planetary atmospheres in the coming decade. Stellar brightness variations due to star spots, however, can impact these measurements and contaminate the observed spectra. Pandora's goal is to disentangle star and planet signals in transmission spectra to reliably determine exoplanet atmosphere compositions. Pandora will collect long-duration photo…
The advent of asteroseismology as the golden path to precisely characterize single stars naturally led to synergies with the field of exoplanetology. Today, the precise determination of stellar masses, radii and ages for exoplanet-host stars is a driving force in the development of dedicated software and techniques to achieve this goal. However, as various approaches exist, it is clear that they all have advantages and inconveniences and that there is a trade-off between accuracy, efficiency, and robustness of the techniques. We aim to compare and discuss various modelling techniques for exopl…
We present the open-source pyratbay framework for exoplanet atmospheric modeling, spectral synthesis, and Bayesian retrieval. The modular design of the code allows the users to generate atmospheric 1D parametric models of the temperature, abundances (in thermochemical equilibrium or constant-with-altitude), and altitude profiles in hydrostatic equilibrium; sample ExoMol and HITRAN line-by-line cross sections with custom resolving power and line-wing cutoff values; compute emission or transmission spectra considering cross sections from molecular line transitions, collision-induced absorption, …
