Knowing the bulk elemental abundances of an exoplanetary atmosphere is not an easy task, but it is crucial to understand the formation history of planets. The purpose of this work is to show that the observability of TiO features at optical wavelengths in the transmission spectra of hot Jupiter atmospheres is sensitive to the bulk chemical properties of the atmosphere. For that, we run a grid of chemical models which include TiO formation and destruction, for the ultra-hot Jupiter WASP-19b and an ultra-hot version of HD~209458b. We take into account non-equilibrium chemistry and changes in the temperature and pressure structure of these atmospheres caused by different C/O ratios. We calculate synthetic transmission spectra for these models, and study the relative strengths of TiO and \ce{H2O} features quantitatively. To compare with observations, we use a model independent metric for molecular abundances, $ΔZ_{\rm TiO-H_2O}/H_{\rm eq}$ that has been previously used in observational studies of exoplanetary atmospheres. We find that with this metric we can differentiate between different chemical models and place constraints on the atmosphere's bulk carbon and oxygen abundance. From chemical considerations we expected that the TiO abundance would depend on the bulk nitrogen, however found that any change to N/H did not result in changes to the resulting TiO. We apply our method to a set of known exoplanets that have been observed in the relevant optical wavelengths and find good agreement between low resolution observations and our model for WASP-121b, marginally good agreement with WASP-79b, WASP-76b, and WASP-19b, and poorer agreement with HD 209458b. Our method can be particularly helpful for indirect studies of the bulk abundances of carbon and oxygen.
One of the desired outcomes of studying exoplanetary atmospheres is to set decisive constraints on exoplanet formation theories. Astronomers often speak of the "metallicity" in broad terms. When modeling the bulk metallicity, workers refer to the elemental iron abundance (Fe/H). By contrast, when exo-atmospheric astronomers speak of the "metallicity" derived from analysing low-resolution Hubble and Spitzer spectrophotometry, they are referring to the elemental abundances of oxygen (O/H), carbon (C/H) and nitrogen (N/H): in decreasing order of importance, since spectra from the Hubble Wide Fiel…
Until recently, infrared observations of exoplanetary atmospheres have typically been interpreted using models that assumed solar elemental abundances. With the chemical composition fixed, attempts have been made to classify hot Jupiter atmospheres on the basis of stellar irradiation. However, recent observations have revealed deviations from predictions based on such classification schemes, and chemical compositions retrieved from some datasets have also indicated non-solar abundances. In hot hydrogen-dominated atmospheres, the C/O ratio critically influences the relative concentrations of se…
JWST Exoplanetary Worlds and Elemental Survey (JEWELS) II: Condensation Temperature Trends and Galactic Chemical Evolution in JWST Planet-Hosting Stars
Tsung-Dao Lee Institute, School of Physics and Astronomy, & State Key Laboratory of Dark Matter Physics, Shanghai Jiao Tong University（上海交通大学物理与天文学院、汤川研究所、暗物质物理国家重点实验室）；Department of Physics, King’s College London（伦敦国王学院物理系）；Department of Astronomy, Tsinghua University（清华大学天文系）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
Solar photospheric abundances of refractory elements mirror the Earth's to within ~10 mol% when normalized to the dominant terrestrial planet-forming elements Mg, Si and Fe. This allows for the adoption of Solar composition as an order-of-magnitude proxy for Earth's. It is not known, however, the degree to which this mirroring of stellar and terrestrial planet abundances holds true for other star-planet systems without determination of the composition of initial planetesimals via condensation sequence calculations and post condensation processes. We present the open-source Arbitrary Compositio…
Earth's tectonic processes regulate the formation of continental crust, control its unique deep water and carbon cycles, and are vital to its surface habitability. A major driver of steady-state plate tectonics on Earth is the sinking of the cold subducting plate into the underlying mantle. This sinking is the result of the combined effects of the thermal contraction of the lithosphere and of metamorphic transitions within the basaltic oceanic crust and lithospheric mantle. The latter of these effects is dependent on the bulk composition of the planet, e.g., the major, terrestrial planet-build…
Recent progress in high-dispersion spectroscopy has revealed the presence of vaporized heavy metals and ions in the atmosphere of hot Jupiters whose dayside temperature is larger than 2000 K, categorized as ultra hot Jupiters (UHJs). Using the archival data of high resolution transmission spectroscopy obtained with the Subaru telescope, we searched for neutral metals in HD149026b, a hot Jupiter cooler than UHJs. By removing stellar and telluric absorption and using a cross-correlation technique, we report tentative detection of neutral titanium with 4.4 sigma and a marginal signal of neutral i…
As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements$-$such as hydrogen, oxygen, carbon, sodium and potassium$-$have in this way been detected in the atmosph…
From Hubble to HWO: Bridging the Frontier of White Dwarf Exoplanet Science
NOIRLab（国家光学红外天文研究实验室）；University of Leicester（莱斯特大学）；University of Victoria（维多利亚大学）；University of Cambridge（剑桥大学）；University of Warwick（华威大学）；Center for Astrophysics — Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；Space Telescope Science Institute（太空望远镜科学研究所）；Université de Montréal（蒙特利尔大学）；Centre de recherche en astrophysique du Québec（魁北克天体物理学研究中心）；Observatoire du Mont-Mégantic（蒙梅格尼克天文台）
One of the primary mechanisms for inferring the dynamical history of planets in our Solar System and in exoplanetary systems is through observation of elemental ratios (i.e. C/O). The ability to effectively use these observations relies critically on a robust understanding of the chemistry and evolutionary history of the observed abundances. Significant efforts have been devoted to this area from within astrochemistry circles, and these efforts should be supported going forward by the larger exoplanetary science community. In addition, the construction of a next-generation radio interferometer…
M dwarfs are prominent targets of planet search projects, and their chemical composition is crucial to understanding the formation process or interior of orbiting exoplanets. However, measurements of elemental abundances of M dwarfs have been limited due to difficulties in the analysis of their optical spectra. We conducted a detailed chemical analysis of five M dwarfs (T_eff ~3200--3800 K), which form binary systems with G/K-type stars, by performing a line-by-line analysis based on high-resolution (R ~80,000) near-infrared (960--1710 nm) spectra obtained with CARMENES. We determined the chem…
High resolution precision spectroscopy provides a multitude of robust techniques for probing exoplanetary atmospheres. We present multiple VLT/ESPRESSO transit observations of the hot-Jupiter exoplanet WASP-19b with previously published but disputed atmospheric features from low resolution studies. Through spectral synthesis and modeling of the Rossiter-McLaughlin (RM) effect we calculate stellar, orbital and physical parameters for the system. From narrow-band spectroscopy we do not detect any of H\,I, Fe\,I, Mg\,I, Ca\,I, Na\,I and K\,I neutral species, placing upper limits on their line con…
Metal Oxide Clusters in Gas Giant Exoplanet Atmospheres
Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）；Institute of Theoretical and Computational Physics, TU Graz（格拉茨工业大学理论与计算物理研究所）；Swiss Federal Institute of Intellectual Property (IGE)（瑞士联邦知识产权局）；Space Research and Planetary Sciences, Physics Institute, University of Bern（伯尔尼大学物理学院空间研究与行星科学系）
A Machine-Learning Compositional Study of Exoplanetary Material Accreted Onto Five Helium-Atmosphere White Dwarfs with $\texttt{cecilia}$
Institute of Astronomy, University of Cambridge（天文学研究所，剑桥大学）；Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology（地球、大气与行星科学系，麻省理工学院）；Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（物理系和卡弗里天体物理与空间研究研究所，麻省理工学院）；Gemini Observatory/NSF’s NOIRLab（Gemini天文台/NSF的NOIRLab）；Département de Physique, Université de Montréal（物理系，蒙特利尔大学）；Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles（地球、行星与空间科学系，加州大学洛杉矶分校）；Department of Physics and Astronomy, University of Victoria（物理与天文学系，维多利亚大学）；Department of Physics and Astronomy, University of California, Los Angeles（物理与天文学系，加州大学洛杉矶分校）
研究首次将机器学习流程 cecilia 用于五颗金属污染氦大气白矮星，通过联合迭代贝叶斯拟合 SDSS 与 Keck/ESI 光谱测定其参数和吸积物元素丰度，发现成分多与 CI 球粒陨石相符且两颗存在显著氧过剩。
The atmospheric C/O ratio of exoplanets is widely used to constrain their formation. To guarantee that the C/O ratio provides robust information, we need to accurately quantify the amount of C and O in exoplanetary atmospheres. In the case of O, water and carbon monoxide are generally studied as the two key carriers. However, oxygen is a very reactive element and does not bind with carbon; depending on the temperature, it also binds to refractory elements. Estimating the amount of oxygen bound to refractory elements is therefore critical for unbiased estimates of the C/O ratio. In this work, w…
The present-day envelope of gaseous planets is a relic of how these giant planets originated and evolved. Measuring their elemental composition therefore presents a powerful opportunity to answer long-standing questions regarding planet formation. Obtaining precise observational constraints on the elemental inventory of giant exoplanets has, however, remained challenging due to the limited simultaneous wavelength coverage of current space-based instruments. Here, we present thermal emission observations of the non-transiting hot Jupiter $τ$ Boo b using the new wide wavelength coverage (0.95$-$…
This work presents a re-analysis of the spectroscopic phase-curve observations of the ultra hot Jupiter WASP-103 b obtained by the Hubble Space Telescope (HST) and the Spitzer Telescope. Traditional 1D and unified 1.5D spectral retrieval techniques are employed, allowing to map the thermal structure and the abundances of trace gases in this planet as a function of longitude. On the day-side, the atmosphere is found to have a strong thermal inversion, with indications of thermal dissociation traced by continuum H- opacity. Water vapor is found across the entire atmosphere but with depleted abun…
Secondary eclipse spectroscopy provides invaluable insights into the temperatures and compositions of exoplanetary atmospheres. We carry out a systematic temperature and abundance retrieval analysis of nine exoplanets (HD189733b, HD209458b, HD149026b, GJ436b, WASP-12b, WASP-19b, WASP-43b, TrES-2b, and TrES-3b) observed in secondary eclipse using a combination of space- and ground-based facilities. Our goal with this analysis is to provide a consistent set of temperatures and compositions from which self-consistent models can be compared and to probe the underlying processes that shape these at…
Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the composition of the nebula from which the systems formed, analogous to how meteorite abundances inform our understanding of the early Solar System. We report the detection of Li, Na, K and Ca in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and with the exception …
The study of exoplanetary atmospheres is key to understand the differences between their physical, chemical and dynamical processes. Up to now, the bulk of atmospheric characterization analysis has been conducted on transiting planets. On some sufficiently bright targets, high-resolution spectroscopy (HRS) has also been successfully tested for non-transiting planets. We study the dayside of the non-transiting planet HD 102195b using the GIANO spectrograph mounted at TNG, demonstrating the feasibility of atmospheric characterization measurements and molecular detection for non-transiting planet…
The breaking of cold traps and onset of titanium in ultra-hot Jupiter atmospheres: WASP-189b in context
Observatoire de Genève, Département d’Astronomie, Université de Genève（日内瓦天文台，天文学系，日内瓦大学）；Institut Trottier de recherche sur les exoplanètes, Département de Physique, Université de Montréal（特罗蒂尔系外行星研究所，物理系，蒙特利尔大学）；Centre Vie dans l’Univers, Faculté des sciences de l’Université de Genève（宇宙生命中心，日内瓦大学理学院）；Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP（空间天体物理学与天文研究所，波尔图大学）；Planétarium de Montréal, Espace pour la Vie（蒙特利尔天文馆，生命空间）；Department of Physics, McGill University（麦吉尔大学物理系）；Department of Earth & Planetary Sciences, McGill University（麦吉尔大学地球与行星科学系）；Univ. Grenoble Alpes, CNRS（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心）
We present a comprehensive analysis of the 0.3--5\,$μ$m transit spectrum for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with Hubble STIS and WFC3 as part of the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program, and we combine those data with warm \textit{Spitzer} transit observations. We extract transit depths from each of the data sets, presenting the STIS transit spectrum (0.29--0.93\,$μ$m) for the first time. We retrieve the transit spectrum both with a free-chemistry retrieval suite (AURA) and a complementary chemical equilibrium retrieval sui…
The super-Earth exoplanet 55 Cnc e, the smallest member of a five-planet system, has recently been observed to transit its host star. The radius estimates from transit observations, coupled with spectroscopic determinations of mass, provide constraints on its interior composition. The composition of exoplanetary interiors and atmospheres are particularly sensitive to elemental C/O ratio, which to first order can be estimated from the host stars. Results from a recent spectroscopic study analyzing the 6300A [O I] line and two C I lines suggest that 55 Cnc has a carbon-rich composition (C/O=1.12…
We present an open-source retrieval code named HELIOS-Retrieval (hereafter HELIOS-R), designed to obtain chemical abundances and temperature-pressure profiles from inverting the measured spectra of exoplanetary atmospheres. In the current implementation, we use an exact solution of the radiative transfer equation, in the pure absorption limit, in our forward model, which allows us to analytically integrate over all of the outgoing rays (instead of performing Gaussian quadrature). Two chemistry models are considered: unconstrained chemistry (where the mixing ratios are treated as free parameter…
Measuring Tracers of Planet Formation in the Atmosphere of WASP-77A b: Sub-stellar O/H and C/H ratios, with a stellar C/O ratio and a potentially Super-stellar Ti/H ratio
The detailed chemical composition of stars is important in many astrophysical fields, among which the characterisation of exoplanetary systems. Previous studies seem to indicate an anomalous chemical pattern of the youngest stellar population in the solar vicinity with a sub-solar metal content. This can influence various observational relations linking the properties of exoplanets to the characteristics of the host stars, for example the giant planet-metallicity relation. In this framework, we aim to expand our knowledge of the chemical composition of intermediate-age stars and understand whe…
A Next-Generation Exoplanet Atmospheric Retrieval Framework for Transmission Spectroscopy (NEXOTRANS): Comparative Characterization for WASP-39 b Using JWST NIRISS, NIRSpec PRISM, and MIRI Observations
Exoplanetary properties depend on stellar properties: to know the planet with accuracy and precision it is necessary to know the star as accurately and precisely as possible. Our immediate aim is to characterize in a homogeneous and accurate way a sample of 27 transiting planet-hosting stars observed within the GAPS program. We determined stellar parameters (effective temperature, surface gravity, rotational velocity) and abundances of 26 elements (Li,C,N,O,Na,Mg,Al,Si,S,Ca,Sc,Ti,V,Cr,Fe,Mn,Co,Ni,Cu,Zn,Y,Zr,Ba,La,Nd,Eu). Our study is based on high-resolution HARPS-N@TNG and FEROS@ESO spectra a…
