The determination of atmospheric structure and molecular abundances of planetary atmospheres via spectroscopy involves direct comparisons between models and data. While varying in sophistication, most model spectra comparisons fundamentally assume one-dimensional (1D) model physics. However, knowledge from general circulation models and of solar system planets suggests that planetary atmospheres are inherently three-dimensional in their structure and composition. We explore the potential biases resulting from standard "1D" assumptions within a Bayesian atmospheric retrieval framework. Specifically, we show how the assumption of a single 1D thermal profile can bias our interpretation of the thermal emission spectrum of a hot Jupiter atmosphere that is composed of two thermal profiles. We retrieve spectra of unresolved model planets as observed with a combination of the Hubble Space Telescope Wide Field Camera 3 (WFC3)+Spitzer Infrared Array Camera (IRAC) as well as the James Webb Space Telescope (JWST) under varying differences in the two thermal profiles. For WFC3+IRAC, there is a significantly biased estimate of CH4 abundance using a 1D model when the contrast is 80%. For JWST, two thermal profiles are required to adequately interpret the data and estimate the abundances when contrast is greater than 40%. We also apply this preliminary concept to the recent WFC3+IRAC phase curve data of the hot Jupiter WASP-43b. We see similar behavior as present in our simulated data: while the H2O abundance determination is robust, CH4 is artificially well-constrained to incorrect values under the 1D assumption. Our work demonstrates the need to evaluate model assumptions in order to extract meaningful constraints from atmospheric spectra and motivates exploration of optimal observational setups.

No description available.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 77-80. / by Dushan Stephen Bukvic. / M.S.

This dissertation explores the consequences of atmospheric dynamics for observations of substellar mass objects (SMOs). Discussed first is the growth of cloud particles of various compositions in brown dwarfs of different surface gravities and effective temperatures. The structure of these objects is calculated with a one-dimensional radiative transfer model. To determine particle sizes, the timescales for microphysical growth processes, including nucleation, coagulation, and coalescence, are compared to the timescale for gravitational sedimentation. The model also allows for sustained uplifting of condensable vapor in convective regions. The results show that particle sizes vary greatly over the range of objects studied. In most cases, clouds on brown dwarfs do not dominate the opacity. Rather, they smooth the emergent spectrum and partially redistribute the radiative energy. The focus then shifts to extrasolar giant planets (EGPs). Results are presented from a three-dimensional model of atmospheric dynamics on the transiting Jupiter-like planet HD 209458b. As a close-in orbiter (known as a “roaster”), HD 209458b is super-heated on its dayside. Due to tidal locking of the interior, the dayside hemisphere faces the star in perpetuity, which leads to very different dynamics than is seen on Jupiter. The flow is characterized by an eastward supersonic jet (u ∼ 4 km s⁻¹) extending from the equator to the mid-latitudes. Temperature contrasts are ∼ 500 K at the photosphere. At 220 mbar, winds blow the hottest regions downstream from the substellar point by ∼ 60°, with direct implications for the infrared light curve. These simulations are extended to the study of carbon chemistry in HD 209458b’s atmosphere by coupling the CO/CH₄ reaction kinetics to the dynamics. Disequilibrium results from slow reaction rates at low temperatures and pressures. Effective vertical quenching near the ∼ 3 bar level leads to uniformly high concentrations of CO at the photosphere, even in cool regions where CH₄ is strongly favored thermodynamically. Observations are underway to detect these signatures of meteorology on HD 209458b and similar planets.

We target the thermal emission spectrum of the non-transiting gas giant HD 88133 b with high-resolution near-infrared spectroscopy, by treating the planet and its host star as a spectroscopic binary. For sufficiently deep summed flux observations of the star and planet across multiple epochs, it is possible to resolve the signal of the hot gas giant's atmosphere compared to the brighter stellar spectrum, at a level consistent with the aggregate shot noise of the full data set. To do this, we first perform a principal component analysis to remove the contribution of the Earth's atmosphere to the observed spectra. Then, we use a cross-correlation analysis to tease out the spectra of the host star and HD 88133 b to determine its orbit and identify key sources of atmospheric opacity. In total, six epochs of Keck NIRSPEC L-band observations and three epochs of Keck NIRSPEC K-band observations of the HD 88133 system were obtained. Based on an analysis of the maximum likelihood curves calculated from the multi-epoch cross-correlation of the full data set with two atmospheric models, we report the direct detection of the emission spectrum of the non-transiting exoplanet HD 88133 b and measure a radial projection of the Keplerian orbital velocity of 40 +/- 15 km s(-1), a true mass of 1.02(-0.28)(+0.61) M-J, a nearly face-on orbital inclination of 15(-5)(+60), and an atmosphere opacity structure at high dispersion dominated by water vapor. This, combined with 11 years of radial velocity measurements of the system, provides the most up-to-date ephemeris for HD 88133.

In this thesis I present near-infrared detections of the thermal emission of a number of hot Jupiters and likely transit depth differences from different wavelength observations of a super-Earth. I have pioneered ``Staring Mode'' using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope to achieve the most accurate photometry to-date in the near-infrared from the ground. I also discuss avenues that should allow one to achieve even more accurate photometry in the future. Using WIRCam on CFHT my collaborators and I have detected the thermal emission of the following hot Jupiters: TrES-2b and TrES-3b in Ks-band, WASP-12b in the J, H \& Ks-bands, and WASP-3b in the Ks-band on two occasions. Near-infrared detections of the thermal emission of hot Jupiters are important, because the majority of these planets' blackbodies peak in this wavelength range; near-infrared detections allow us to obtain the most model-independent constraints on these planets' atmospheric characteristics, their temperature-pressure profiles with depth and an estimate of their bolometric luminosities. With these detections we are able to answer such questions as: how efficiently these planets redistribute heat to their nightsides, if they're being inflated by tidal heating, whether there's any evidence that one of these planets is precessing, and whether another experiences extreme weather and violent storms? My collaborators and I have also observed several transits of the super-Earth GJ 1214b. We find a deeper transit depth in one of our near-infrared bands than the other. This is likely indicative of a spectral absorption feature. For the differences in the transit depth to be as large as we observed, the atmosphere of GJ 1214b must have a large scale height, low mean molecular weight and thus have a hydrogen/helium dominated atmosphere. Given that other researchers have not found similar transit depth differences, we also discuss the most likely atmospheric makeup for this planet that results from a combination of all the observations to date. Lastly, by searching for long-term linear trends in radial velocity data, I constrain the theory that most hot Jupiters migrated to their present positions via the Kozai mechanism with tidal heating.

In this thesis I present near-infrared detections of the thermal emission of a number of hot Jupiters and likely transit depth differences from different wavelength observations of a super-Earth. I have pioneered ``Staring Mode'' using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope to achieve the most accurate photometry to-date in the near-infrared from the ground. I also discuss avenues that should allow one to achieve even more accurate photometry in the future. Using WIRCam on CFHT my collaborators and I have detected the thermal emission of the following hot Jupiters: TrES-2b and TrES-3b in Ks-band, WASP-12b in the J, H \& Ks-bands, and WASP-3b in the Ks-band on two occasions. Near-infrared detections of the thermal emission of hot Jupiters are important, because the majority of these planets' blackbodies peak in this wavelength range; near-infrared detections allow us to obtain the most model-independent constraints on these planets' atmospheric characteristics, their temperature-pressure profiles with depth and an estimate of their bolometric luminosities. With these detections we are able to answer such questions as: how efficiently these planets redistribute heat to their nightsides, if they're being inflated by tidal heating, whether there's any evidence that one of these planets is precessing, and whether another experiences extreme weather and violent storms? My collaborators and I have also observed several transits of the super-Earth GJ 1214b. We find a deeper transit depth in one of our near-infrared bands than the other. This is likely indicative of a spectral absorption feature. For the differences in the transit depth to be as large as we observed, the atmosphere of GJ 1214b must have a large scale height, low mean molecular weight and thus have a hydrogen/helium dominated atmosphere. Given that other researchers have not found similar transit depth differences, we also discuss the most likely atmospheric makeup for this planet that results from a combination of all the observations to date. Lastly, by searching for long-term linear trends in radial velocity data, I constrain the theory that most hot Jupiters migrated to their present positions via the Kozai mechanism with tidal heating.

Thesis (PHD)--University of Montana, 2009. / Contents viewed on December 18, 2009. Title from author supplied metadata. Includes bibliographical references.

This work describes the observations and results found from a photometric survey of a 0.5° by 0.5° area of the Galactic Plane performed using the 2.2 metre ESO telescope at La Silla, Chile. The dataset comprises a total of 267 images with 204 from a 16 day observation run in 2005 and 63 from a six week observation run in 2002. The new image subtraction reduction algorithm implemented on this data resulted in more than 500,000 lightcurves with a magnitude limit of R ~ 24.5. The precision of the data following reduction is suitable for transit searches as well as identification of variable stars. Resulting from the transit search was an initial list of 31 candidates, reducing to 23 on further examination. Nine candidates were eliminated by examination of the images and the remaining list re-reduced. After this reduction three good candidates remain. These candidates have periods from 1.2840 to 2.6269 days and depths of around 75 mmags. These three candidates require followup of either multi-colour photometry or spectroscopy to determine their nature. The variable star search resulted in detections of 1475 variable stars of different types. The largest portion were eclipsing binary stars. A number of the contact binaries have possible low mass-ratios and there are also a number of contact and detached binaries which may contain low-mass components. Three of the contact binaries were found to have periods at the known period cut off including two with periods lower than any previously published. Also identified were two possible pre-main sequence detached eclipsing binaries. The binary fraction of the field was calculated from the observed contact binaries to be 46% ± 4%. There are a number of possibilities for further data mining of the survey.

This work describes the observations and results found from a photometric survey of a 0.5° by 0.5° area of the Galactic Plane performed using the 2.2 metre ESO telescope at La Silla, Chile. The dataset comprises a total of 267 images with 204 from a 16 day observation run in 2005 and 63 from a six week observation run in 2002. The new image subtraction reduction algorithm implemented on this data resulted in more than 500,000 lightcurves with a magnitude limit of R ~ 24.5. The precision of the data following reduction is suitable for transit searches as well as identification of variable stars. Resulting from the transit search was an initial list of 31 candidates, reducing to 23 on further examination. Nine candidates were eliminated by examination of the images and the remaining list re-reduced. After this reduction three good candidates remain. These candidates have periods from 1.2840 to 2.6269 days and depths of around 75 mmags. These three candidates require followup of either multi-colour photometry or spectroscopy to determine their nature. The variable star search resulted in detections of 1475 variable stars of different types. The largest portion were eclipsing binary stars. A number of the contact binaries have possible low mass-ratios and there are also a number of contact and detached binaries which may contain low-mass components. Three of the contact binaries were found to have periods at the known period cut off including two with periods lower than any previously published. Also identified were two possible pre-main sequence detached eclipsing binaries. The binary fraction of the field was calculated from the observed contact binaries to be 46% ± 4%. There are a number of possibilities for further data mining of the survey.