Observations, Thermochemical Calculations, and Modeling of Exoplanetary Atmospheres

This dissertation as a whole aims to provide the means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations to characterize planetary atmospheres. We chose targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty. Chapter 1 gives a short introduction. Chapter 2 presents the Spitzer secondary-eclipse analysis and atmospheric characterization of WASP-14b. The decrease in flux when a planet passes behind its host star reveals the planet dayside thermal emission, which, in turn, tells us about the atmospheric temperature and pressure profiles and molecular abundances. WASP-14b is a highly irradiated, transiting hot Jupiter. By applying a Bayesian approach in the atmospheric analysis, we found an absence of thermal inversion contrary to theoretical predictions. Chapter 3 describes the infrared observations of WASP-43b\u27s Spitzer secondary eclipses, data analysis, and atmospheric characterization. WASP-43b is one of the closest-orbiting hot Jupiters, orbiting one of the coolest stars with a hot Jupiter. This configuration provided one of the strongest signal-to-noise ratios. The atmospheric analysis ruled out a strong thermal inversion in the dayside atmosphere of WASP-43b and put a nominal upper limit on the day-night energy redistribution. Chapter 4 presents an open-source Thermochemical Equilibrium Abundances (TEA) code and its application to several hot-Jupiter temperature and pressure models. TEA calculates the abundances of gaseous molecular species using the Gibbs free-energy minimization method within an iterative Lagrangian optimization scheme. The thermochemical equilibrium abundances obtained with TEA can be used to initialize atmospheric models of any planetary atmosphere. The code is written in Python, in a modular fashion, and it is available to the community via http://github.com/dzesmin/TEA. Chapter 5 presents my contributions to an open-source Bayesian Atmospheric Radiative Transfer (BART) code, and its application to WASP-43b. BART characterizes planetary atmospheres based on the observed spectroscopic information. It initializes a planetary atmospheric model, performs radiative-transfer calculations to produce models of planetary spectra, and using a statistical module compares models with observations. We describe the implementation of the initialization routines, the atmospheric profile generator, the eclipse module, the best-fit routines, and the contribution function module. We also present a comprehensive atmospheric analysis of all WASP-43b secondary-eclipse data obtained from the space- and ground-based observations using BART

Observations, Thermochemical Calculations, and Modeling of Exoplanetary Atmospheres

This dissertation as a whole aims to provide means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations and targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty. Chapter 1 gives a short introduction. Chapter 2 presents the Spitzer secondary-eclipse analysis and atmospheric characterization of WASP-14b. WASP-14b is a highly irradiated, transiting hot Jupiter. By applying a Bayesian approach in the atmospheric analysis, we found an absence of thermal inversion contrary to theoretical predictions. Chapter 3 describes the infrared observations of WASP-43b Spitzer secondary eclipses, data analysis, and atmospheric characterization. WASP-43b is one of the closest-orbiting hot Jupiters, orbiting one of the coolest stars with a hot Jupiter. The atmospheric analysis ruled out a strong thermal inversion in its dayside atmosphere. Chapter 4 presents an open-source Thermochemical Equilibrium Abundances (TEA) code and its application to several hot Jupiters. TEA calculates the abundances of gaseous species using the Gibbs free-energy minimization method within an iterative Lagrangian optimization scheme. The code is written in Python and available to the community via http://github.com/dzesmin/TEA. Chapter 5 presents my contributions to an open-source Bayesian Atmospheric Radiative Transfer (BART) code, and its application to WASP-43b. BART characterizes planetary atmospheres based on the observed spectroscopic information. It initializes a planetary atmospheric model, performs radiative-transfer calculations to produce models of planetary spectra, and using a statistical module compares models with observations.Comment: Ph.D. Dissertatio

TEA: A Code for Calculating Thermochemical Equilibrium Abundances

We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. (1958) and Eriksson (1971). It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature-pressure pairs. We tested the code against the method of Burrows & Sharp (1999), the free thermochemical equilibrium code CEA (Chemical Equilibrium with Applications), and the example given by White et al. (1958). Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.Comment: 14 pages, 8 figures, article is submitted to ApJS, posted on arXiv for public commentary, please send comments to the lead autho

Rousseausches Erbe in Rawls’ Moralpsychologie

Rousseauov utjecaj na Rawlsov izvoran argument za pravdu kao poštenje neki su autori primijetili, ali malo je njih raspravljalo o Rousseauovu utjecaju na Rawlsovu psihologiju morala koja sačinjava prvi dio njegova argumenta o stabilnosti. Argumentirat ću da Rawlsov iskaz o moralnom razvoju podudara i zasniva se na Rousseauovu konceptu amour propre. Napose tvrdim da je (1) Rawlsova teza da osjećaj za pravdu proizlazi iz ljubavi i prijateljstva prikaz Rousseauove teze da moralni sentimenti proizlaze iz prirodnih sentimenata, da se (2) Rawlsovo objašnjenje o tome kako zadobivamo reciprocitet dispozicija zasniva na Rousseauovu objašnjenju kako amour-propre može biti produžen u smisao pravde, te da (3) Rawlsova misao o principu simpatije odgovara Rousseauovim mislima o suosjećajnosti.Some authors have noticed Rousseau\u27s influence on Rawls\u27s original position argument for justice as fairness, but few have argued for Rousseau’s influence on his moral psychology, which constitutes the first part of his stability argument. I will argue that Rawls’s account of moral development parallels, and is grounded in, Rousseau’s thoughts on amour-propre. In particular, I argue that (1) Rawls’s thesis that the sense of justice is derived from love and friendship is an illustration of Rousseau’s thesis that moral sentiments are derived from natural sentiments, that (2) Rawls’s explanation for how we acquire the reciprocity of disposition is grounded in Rousseau’s explanation of how amour-propre can be extended into the sense of justice, and that (3) Rawls’s thoughts on the principle of sympathy parallel Rousseau’s thoughts on compassion.Certains auteurs ont remarqué l’influence de Rousseau sur l’argument de la position originelle de Rawls en faveur de la justice comme équité, mais peu ont argumenté en faveur de l’influence de Rousseau sur sa psychologie morale, qui constitue la première partie de son argument de la stabilité. Je soutiendrai que le compte-rendu de Rawls sur le développement moral est un parallèle et il se fonde sur les réflexions de Rousseau sur l’amour-propre. En particulier, je soutiens que (1) la thèse de Rawls selon laquelle le sens de la justice procède de l’amour et de l’amitié est une illustration de la thèse de Rousseau selon laquelle les sentiments moraux procèdent de sentiments naturels, que (2) l’explication de Rawls sur la manière d’acquérir la réciprocité des dispositions est fondée sur l’explication de Rousseau sur la manière dont l’amour-propre peut être étendu au sens de la justice et que (3) les réflexions de Rawls sur le principe de sympathie correspondent aux pensées de Rousseau sur la compassion.Rousseaus Einflussnahme auf Rawls’ ursprüngliches Argument für Gerechtigkeit als Fairness wurde zwar von einigen Autoren bemerkt, jedoch nur wenige haben sich für Rousseaus Einfluss auf Rawls’ Moralpsychologie ausgesprochen, die den ersten Teil seines Stabilitätsarguments ausmacht. Ich werde substanziieren, dass Rawls’ Bericht über die moralische Entwicklung mit Rousseaus Gedanken über die amour-propre übereinstimmt und darauf aufbaut. Insbesondere argumentiere ich, dass (1) Rawls’ These, der Sinn für Gerechtigkeit rühre von Liebe und Freundschaft her, eine Illustration von Rousseaus These ist, dass moralische Empfindungen auf natürlichen Empfindungen beruhen, dass (2) Rawls’ Auslegung, wie wir die Reziprozität der Disposition erlangen, auf Rousseaus Erklärung basiert, wie amour-propre auf den Gerechtigkeitssinn ausgedehnt werden kann und dass (3) Rawls’ Gedanken zum Prinzip der Sympathie mit Rousseaus Gedanken zum Mitgefühl korrespondieren

Spitzer observations of the thermal emission from WASP-43b

WASP-43b is one of the closest-orbiting hot Jupiters, with a semimajor axis of a = 0.01526 +/- 0.00018 AU and a period of only 0.81 days. However, it orbits one of the coolest stars with a hot Jupiter (Tstar = 4520 +/- 120 K), giving the planet a modest equilibrium temperature of Teq = 1440 +/- 40 K, assuming zero Bond albedo and uniform planetary energy redistribution. The eclipse depths and brightness temperatures from our jointly fit model are 0.347% +/- 0.013% and 1670 +/- 23 K at 3.6 {\mu}m and 0.382% +/- 0.015% and 1514 +/- 25 K at 4.5 {\mu}m. The eclipse timings improved the estimate of the orbital period, P, by a factor of three (P = 0.81347436 +/- 1.4*10-7 days) and put an upper limit on the eccentricity (e = 0.010+0.010 -0.007). We use our Spitzer eclipse depths along with four previously reported ground-based photometric observations in the near-infrared to constrain the atmospheric properties of WASP-43b. The data rule out a strong thermal inversion in the dayside atmosphere of WASP-43b. Model atmospheres with no thermal inversions and fiducial oxygen-rich compositions are able to explain all the available data. However, a wide range of metallicities and C/O ratios can explain the data. The data suggest low day-night energy redistribution in the planet, consistent with previous studies, with a nominal upper limit of about 35% for the fraction of energy incident on the dayside that is redistributed to the nightside.Comment: 11 pages, 9 figure

Infrared Eclipses of the Strongly Irradiated Planet WASP-33b, and Oscillations of its Host Star

We observe two secondary eclipses of the strongly irradiated transiting planet WASP-33b in the Ks band, and one secondary eclipse each at 3.6- and 4.5 microns using Warm Spitzer. This planet orbits an A5V delta-Scuti star that is known to exhibit low amplitude non-radial p-mode oscillations at about 0.1-percent semi-amplitude. We detect stellar oscillations in all of our infrared eclipse data, and also in one night of observations at J-band out of eclipse. The oscillation amplitude, in all infrared bands except Ks, is about the same as in the optical. However, the stellar oscillations in Ks band have about twice the amplitude as seen in the optical, possibly because the Brackett-gamma line falls in this bandpass. We use our best-fit values for the eclipse depth, as well as the 0.9 micron eclipse observed by Smith et al., to explore possible states of the exoplanetary atmosphere, based on the method of Madhusudhan and Seager. On this basis we find two possible states for the atmospheric structure of WASP-33b. One possibility is a non-inverted temperature structure in spite of the strong irradiance, but this model requires an enhanced carbon abundance (C/O>1). The alternative model has solar composition, but an inverted temperature structure. Spectroscopy of the planet at secondary eclipse, using a spectral resolution that can resolve the water vapor band structure, should be able to break the degeneracy between these very different possible states of the exoplanetary atmosphere. However, both of those model atmospheres absorb nearly all of the stellar irradiance with minimal longitudinal re-distribution of energy, strengthening the hypothesis of Cowan et al. that the most strongly irradiated planets circulate energy poorly. Our measurement of the central phase of the eclipse yields e*cos(omega)=0.0003 +/-0.00013, which we regard as being consistent with a circular orbit.Comment: 23 pages, 9 figures, 3 tables, accepted for the Astrophysical Journa

Imaging Cool Giant Planets in Reflected Light: Science Investigations and Synergy with Habitable Planets

Planned astronomical observatories of the 2020s will be capable of obtaining reflected light photometry and spectroscopy of cool extrasolar giant planets. Here we explain that such data are valuable both for understanding the origin and evolution of giant planets as a whole and for preparing for the interpretation of similar datasets from potentially habitable extrasolar terrestrial planets in the decades to follow.Comment: Science white paper submitted to the Astro 2020 Decadal Survey on Astronomy and Astrophysics. Replace version to fix typo in co-signer name and add figure credit

Thermal Emission of WASP-14b Revealed with Three Spitzer Eclipses

Exoplanet WASP-14b is a highly irradiated, transiting hot Jupiter. Joshi et al. calculate an equilibrium temperature Teq of 1866 K for zero albedo and reemission from the entire planet, a mass of 7.3 +/- 0.5 Jupiter masses and a radius of 1.28 +/- 0.08 Jupiter radii. Its mean density of 4.6 g/cm3 is one of the highest known for planets with periods less than 3 days. We obtained three secondary eclipse light curves with the Spitzer Space Telescope. The eclipse depths from the best jointly fit model are $0.224\%$ +/- $0.018\%$ at 4.5 {\mu}m and $0.181\%$ +/- $0.022\%$ at 8.0 {\mu}m. The corresponding brightness temperatures are 2212 +/- 94 K and 1590 +/- 116 K. A slight ambiguity between systematic models suggests a conservative 3.6 {\mu}m eclipse depth of $0.19\%$ +/- $0.01\%$ and brightness temperature of 2242 +/- 55 K. Although extremely irradiated, WASP-14b does not show any distinct evidence of a thermal inversion. In addition, the present data nominally favor models with day night energy redistribution less than $~30\%$. The current data are generally consistent with oxygen-rich as well as carbon-rich compositions, although an oxygen-rich composition provides a marginally better fit. We confirm a significant eccentricity of e = 0.087 +/- 0.002 and refine other orbital parameters.Comment: 16 pages, 16 figure

Two nearby sub-Earth-sized exoplanet candidates in the GJ 436 system

We report the detection of UCF-1.01, a strong exoplanet candidate with a radius 0.66 +/- 0.04 times that of Earth (R_{\oplus}). This sub-Earth-sized planet transits the nearby M-dwarf star GJ 436 with a period of 1.365862 +/- 8x10^{-6} days. We also report evidence of a 0.65 +/- 0.06 R_{\oplus} exoplanet candidate (labeled UCF-1.02) orbiting the same star with an undetermined period. Using the Spitzer Space Telescope, we measure the dimming of light as the planets pass in front of their parent star to assess their sizes and orbital parameters. If confirmed, UCF-1.01 and UCF-1.02 would be called GJ 436c and GJ 436d, respectively, and would be part of the first multiple-transiting-planet system outside of the Kepler field. Assuming Earth-like densities of 5.515 g/cm^3, we predict both candidates to have similar masses (~0.28 Earth-masses, M_{\oplus}, 2.6 Mars-masses) and surface gravities of ~0.65 g (where g is the gravity on Earth). UCF-1.01's equilibrium temperature (T_{eq}, where emitted and absorbed radiation balance for an equivalent blackbody) is 860 K, making the planet unlikely to harbor life as on Earth. Its weak gravitational field and close proximity to its host star imply that UCF-1.01 is unlikely to have retained its original atmosphere; however, a transient atmosphere is possible if recent impacts or tidal heating were to supply volatiles to the surface. We also present additional observations of GJ 436b during secondary eclipse. The 3.6-micron light curve shows indications of stellar activity, making a reliable secondary eclipse measurement impossible. A second non-detection at 4.5 microns supports our previous work in which we find a methane-deficient and carbon monoxide-rich dayside atmosphere.Comment: Accepted for publication with Ap