The Upsilon Andromedae system was the first multi-planet system discovered orbiting a main-sequence star. We describe the detection of water vapor in the atmosphere of the innermost non-transiting gas giant ups. And. b by treating the star-planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve the signal of the planet's motion and break the mass-inclination degeneracy for this non-transiting planet via deep combined flux observations of the star and the planet. In total, seven epochs of Keck NIRSPEC L band observations, three epochs of Keck NIRSPEC short-wavelength K band observations, and three epochs of Keck NIRSPEC long wavelength K band observations of the ups. And. system were obtained. We perform a multi-epoch cross-correlation of the full data set with an atmospheric model. We measure the radial projection of the Keplerian velocity (K-P = 55 +/- 9 km s(-1)), true mass (M-b = 1.7(-0.24)(+0.33)M(J)), and orbital inclination (i(b) 24 degrees +/- 4 degrees), and determine that the planet's opacity structure is dominated by water vapor at the probed wavelengths. Dynamical simulations of the planets in the ups. And. system with these orbital elements for ups. And. b show that stable, long-term (100 Myr) orbital configurations exist. These measurements will inform future studies of the stability and evolution of the ups. And. system, as well as the atmospheric structure and composition of the hot Jupiter.

We present spectrophotometry spanning 1-5 mu m of 51 Eridani b, a 2-10 M-Jup planet discovered by the Gemini Planet Imager Exoplanet Survey. In this study, we present new K1 (1.90-2.19 mu m) and K2 (2.10-2.40 mu m) spectra taken with the Gemini Planet Imager as well as an updated L-P (3.76 mu m) and new M-S (4.67 mu m) photometry from the NIRC2 Narrow camera. The new data were combined with J (1.13-1.35 mu m) and H (1.50-1.80 mu m) spectra from the discovery epoch with the goal of better characterizing the planet properties. The 51 Eri b photometry is redder than field brown dwarfs as well as known young T-dwarfs with similar spectral type (between T4 and T8), and we propose that 51 Eri b might be in the process of undergoing the transition from L-type to T-type. We used two complementary atmosphere model grids including either deep iron/silicate clouds or sulfide/salt clouds in the photosphere, spanning a range of cloud properties, including fully cloudy, cloud-free, and patchy/intermediate-opacity clouds. The model fits suggest that 51 Eri. b has an effective temperature ranging between 605 and 737 K, a solar metallicity, and a surface gravity of log(g) = 3.5-4.0 dex, and the atmosphere requires a patchy cloud atmosphere to model the spectral energy distribution (SED). From the model atmospheres, we infer a luminosity for the planet of -5.83 to -5.93 (logL/L circle dot),leaving 51 Eri b in the unique position of being one of the only directly imaged planets consistent with having formed via a cold-start scenario. Comparisons of the planet SED against warm-start models indicate that the planet luminosity is best reproduced by a planet formed via core accretion with a core mass between 15 and 127 M-circle plus.

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Dust grains are a crucial component of disks around young stellar systems where current observations and theory show that planets form. Dust grains must grow 10 orders of magnitude in size to become planets. However, one of the early steps in this growth phase faces stringent theoretical constraints. The metre barrier relates to two well-studied physical mechanisms which inhibit grain growth beyond centimetre sizes. We report on numerical studies which probe these early stages of planet formation including instabilities that promote dust concentration such as the streaming instability (SI). We explore several different SPH models for dusty gas evolution. We find the linear SI is difficult for SPH to capture because it begins with perturbations below the 1% level. We also employ the Athena 3rd order Eulerian code which has been used to study the SI in the linear phase and the non-linear or saturated phase. We present numerical confirmations of recent analytical predictions of enhancements to the SI growth rates caused by the dust settling to the disk midplane in the earliest stages of the protoplanetary disk evolution. Symmetric analytical predictions for SI growth are not directly relevant to the non-axisymetric, planar geometry of the saturated, non-linear phase. We lay the ground work to explore this in future work. / Thesis / Master of Science (MSc)

The discovery and characterization of exoplanetary systems is a new exciting field. At just over two decades old, it has already fundamentally reshaped our knowledge of planet and solar system formation. We now know that there is a vast diversity of planetary systems, in highly varied, even bizarre, configurations. Known planetary bodies span all masses from objects less massive and smaller than Earth to objects as large as the smallest stars or brown dwarfs. They exhibit periods of but a few hours to periods spanning millennia, from nearly perfectly circular orbits to highly elliptical, from fluffy gas giants to dense rocky worlds, from purely metallic worlds to water worlds. Exoplanets come in all sizes, compositions and varieties. These new discoveries have fundamentally changed the way we approach planetary science. With such a great diversity in exoplanets, we look extend our knowledge to including understanding their individual composition. We wish to understand the climate of these exoplanets and to resolve the differences between, for example, Earth-like and Venus-like planets. To facilitate these discoveries several methods of exoplanery detection and characterization have been developed. Among them are indirect methods that infer the existence of exoplanets from their influence on their star, and direct methods that detect the light from the exoplanets themselves. Direct detection of exoplanets allows not only for a determination of the existence of the object, but also for the determination of its composition and climate through the measurement of its atmosphere's chemical composition. Using purely high-contrast direct imaging methods, coarse spectra can now be measured for exoplanets with a relative brightness 10⁻⁴-10⁻⁵ below that of the host star. Below this contrast level the companion is at the same level of brightness as the noise caused by optical defects and wave front errors in the observed light, called speckles. In this thesis, I demonstrate the usage and optimization of a new novel technique, S4_Spectrum, to model and remove speckle noise from directly imaged systems. S4_Spectrum is capable of reducing 99% of the speckle noise. This allows for the detection and spectral characterization of exoplanets as faint as 10⁻⁶-10⁻⁷ times the brightness of their host stars. This represents two orders of magnitude gain in sensitivity. I present the design of one of these high-contrast systems, Project 1640, as well as the data collection method, including the data pipeline and analysis techniques. Also, I describe the S4_Spectrum technique in detail, as implemented in Project 1640, and present its operation and optimization. Additionally, I present the application of this new tool to obtain several spectral characterizations of objects found in the Project 1640 survey.

Since the discovery of 51 Pegasi b in 1995, continued observations have indirectly identified over 110 planetary objects. These Jupiter-mass objects cause their host star to "wobble" slightly about the common centre-of-mass of the system, which is detectable as radial motion in high-precision Doppler spectroscopy. Of the known planets, approximately 20% are found to orbit within 0.1 AU of the star, whilst the transit of HD209458 has inferred the gas-giant nature of these close-in extrasolar giant planets (CEGPs). The discovery of CEGPs has produced a wave of speculative theory as to the exact nature of these objects, and how they came to exist so close to their parent star. Our spectroscopic technique provides a method of achieving the direct detection of a CEGP atmosphere, the results of which will allow us to test emerging models that aim to predict the atmospheric nature of CEGPs and may provide additional information on the orbital inclination and mass of the planet. We start with a historical review of the field of extrasolar planets, followed by an introduction to the fundamental concepts which underpin the reflection of starlight from a planet's surface. We then investigate the prospects of detecting such a reflection, before detailing the technique we have devised and applied here to two known CEGP hosts. In the first instance, r Bootis, we combined observations at the 4.2-m William Herschel telescope in 1998, 1999 and 2000. The dataset comprised 893 high-resolution échelle spectra with a total integration time of 75hr 32min spanning 17 nights. We establish an upper limit on the planet's geometric albedo p < 0.39 (at the 99.9% significance level) at the most probable orbital inclination i ~ 36 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp - 1.2RJup. Although a weak candidate signal appears near to the most probable radial velocity amplitude, its statistical significance is insufficient for us to claim a detection with any confidence. In the second instance, HD75289, 4 nights of VLT(UT2)/UVES observations were secured in 2003 Jan, yielding 684 high-resolution spectra with a total integration time of 26 hours. We establish an upper limit on the planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the most probable orbital inclination i ~/= 60 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp = 1.6RJup. In both cases, we are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks.

The full-phase infrared light curves of low-eccentricity hot Jupiters show a trend of increasing fractional dayside-nightside brightness temperature difference with increasing incident stellar flux, both averaged across the infrared and in each individual wavelength band. The analytic theory of Komacek & Showman shows that this trend is due to the decreasing ability with increasing incident stellar flux of waves to propagate from day to night and erase temperature differences. Here, we compare the predictions of this theory with observations, showing that it explains well the shape of the trend of increasing dayside-nightside temperature difference with increasing equilibrium temperature. Applied to individual planets, the theory matches well with observations at high equilibrium temperatures but, for a fixed photosphere pressure of 100 mbar, systematically underpredicts the dayside-nightside brightness temperature differences at equilibrium temperatures less than 2000 K. We interpret this as being due to the effects of a process that moves the infrared photospheres of these cooler hot Jupiters to lower pressures. We also utilize general circulation modeling with double-gray radiative transfer to explore how the circulation changes with equilibrium temperature and drag strengths. As expected from our theory, the dayside-nightside temperature differences from our numerical simulations increase with increasing incident stellar flux and drag strengths. We calculate model phase curves using our general circulation models, from which we compare the broadband infrared offset from the substellar point and dayside-nightside brightness temperature differences against observations, finding that strong drag or additional effects (e.g., clouds and/or supersolar metallicities) are necessary to explain many observed phase curves.

Massive circumstellar disks are prone to gravitational instabilities, which trigger the formation of spiral arms that can fragment into bound clumps under the right conditions. Two-dimensional simulations of self-gravitating disks are useful starting points for studying fragmentation because they allow high-resolution simulations of thin disks. However, convergence issues can arise in 2D from various sources. One of these sources is the 2D approximation of self-gravity, which exaggerates the effect of self-gravity on small scales when the potential is not smoothed to account for the assumed vertical extent of the disk. This effect is enhanced by increased resolution, resulting in fragmentation at longer cooling timescales beta. If true, it suggests that the 3D simulations of disk fragmentation may not have the same convergence problem and could be used to examine the nature of fragmentation without smoothing self-gravity on scales similar to the disk scale height. To that end, we have carried out local 3D self-gravitating disk simulations with simple beta cooling with fixed background irradiation to determine if 3D is necessary to properly describe disk fragmentation. Above a resolution of similar to 40 grid cells per scale height, we find that our simulations converge with respect to the cooling timescale. This result converges in agreement with analytic expectations which place a fragmentation boundary at beta(crit) = 3.

We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HATP-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2-4.6s, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.

The amount of light an exoplanet reflects and emits towards an observer waxes and wanes as the planet orbits through its phases. The amplitude and profile of reflection phase curves constrain the albedo of planetary surfaces and atmospheres, while the thermal amplitude and profile reveal temperature distributions and heat transport efficiencies, all providing valuable insight into the nature of exoplanet surfaces and atmospheres. In this dissertation I highlight the usefulness of utilizing full orbital phase curves in addition to occultation measurements, which provides a higher sensitivity to planetary photons at the expense of a more challenging data reduction. In the first few chapters of this dissertation, I introduce a novel non-parametric algorithm to produce clean, robust exoplanet phase curves, and apply it to separate ensembles of 115 Neptunian and 50 Terran exoplanets observed by the Kepler satellite to measure an upper limit on the average albedo of Kepler’s Neptunian planets, and make the first constraint on the average albedo of Terran worlds. In the fourth chapter, I present the full orbital phase curve and occultation of the ultra-hot Jupiter WASP-100b observed by the Transiting Exoplanet Survey Satellite (TESS), and with the use of Bayesian methods, present the first measurement of a phase shift of the thermal maximum among the phase curves observed by TESS, the degree of which challenges the predicted efficiency of heat transport in the atmospheres of ultra-hot Jupiters. In the final chapter, I present an example of how the NASA ROCKE-3D general circulation model can be used to explore the physical mechanisms that influence the habitability of terrestrial exoplanets, and then show how I generated phase curves from the 3-dimensional models to study the signals produced by simulated TRAPPIST-1 habitable-zone worlds. The work in this dissertation contributes valuable new information to the astronomical literature and provides avenues for further research on the nature of short-period exoplanets.