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- All Subjects: Extrasolar planets
- Creators: Butler, Nathaniel
- Creators: Garhart, Emily
Description
The field of exoplanet science has matured over the past two decades with over 3500 confirmed exoplanets. However, many fundamental questions regarding the composition, and formation mechanism remain unanswered. Atmospheres are a window into the properties of a planet, and spectroscopic studies can help resolve many of these questions. For the first part of my dissertation, I participated in two studies of the atmospheres of brown dwarfs to search for weather variations. To understand the evolution of weather on brown dwarfs we conducted a multi-epoch study monitoring four cool brown dwarfs to search for photometric variability. These cool brown dwarfs are predicted to have salt and sulfide clouds condensing in their upper atmosphere and we detected one high amplitude variable. Combining observations for all T5 and later brown dwarfs we note a possible correlation between variability and cloud opacity.
For the second half of my thesis, I focused on characterizing the atmospheres of directly imaged exoplanets. In the first study Hubble Space Telescope data on HR8799, in wavelengths unobservable from the ground, provide constraints on the presence of clouds in the outer planets. Next, I present research done in collaboration with the Gemini Planet Imager Exoplanet Survey (GPIES) team including an exploration of the instrument contrast against environmental parameters, and an examination of the environment of the planet in the HD 106906 system. By analyzing archival HST data and examining the near-infrared colors of HD 106906b, we conclude that the companion shows weak evidence of a circumplanetary dust disk or cloud. Finally, I measure the properties of the low mass directly imaged planet 51 Eridani b. We combined published J, H spectra with updated LP photometry, new K1, K2 spectra, and MS photometry. The new data confirms that the planet has redder than similar spectral type objects, which might be due to the planet still transitioning from to L-to-T. Model atmospheres indicate a cooler effective temperature best fit by a patchy cloud atmosphere making 51 Eri b an excellent candidate for future variability studies with the James Webb Space Telescope.
For the second half of my thesis, I focused on characterizing the atmospheres of directly imaged exoplanets. In the first study Hubble Space Telescope data on HR8799, in wavelengths unobservable from the ground, provide constraints on the presence of clouds in the outer planets. Next, I present research done in collaboration with the Gemini Planet Imager Exoplanet Survey (GPIES) team including an exploration of the instrument contrast against environmental parameters, and an examination of the environment of the planet in the HD 106906 system. By analyzing archival HST data and examining the near-infrared colors of HD 106906b, we conclude that the companion shows weak evidence of a circumplanetary dust disk or cloud. Finally, I measure the properties of the low mass directly imaged planet 51 Eridani b. We combined published J, H spectra with updated LP photometry, new K1, K2 spectra, and MS photometry. The new data confirms that the planet has redder than similar spectral type objects, which might be due to the planet still transitioning from to L-to-T. Model atmospheres indicate a cooler effective temperature best fit by a patchy cloud atmosphere making 51 Eri b an excellent candidate for future variability studies with the James Webb Space Telescope.
ContributorsRajan, Abhijith (Author) / Patience, Jennifer (Thesis advisor) / Young, Patrick (Thesis advisor) / Scowen, Paul (Committee member) / Butler, Nathaniel (Committee member) / Shkolnik, Evgenya (Committee member) / Arizona State University (Publisher)
Created2017
Description
The 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6- and 4.5 μm using the Spitzer Space Telescope is here reported. Eclipse results for 27 of these planets are new and include highly irradiated worlds such as KELT-7b (Kilodegree Extremely Little Telescope), WASP-87b (Wide Angle Search for Planets), WASP-76b, and WASP-64b, and important targets for the James Webb Space Telescope (JWST) such as WASP-62b. WASP-62b is found to have a slightly eccentric orbit (ecosω=0.00614±0.00058), and the eccentricities of HAT-P-13b (Hungarian Automated Telescope Project) and WASP-14b are confirmed. The remainder are individually consistent with circular orbits, but there is statistical evidence for eccentricity increasing with orbital period in this range from 1 to 5 days. Day-side brightness temperatures (Tb) for the planets yield information on albedo and heat redistribution, following Cowan and Agol (2011). Planets having maximum day side temperatures exceeding ∼2200 K are consistent with zero albedo and distribution of stellar irradiance uniformly over the day-side hemisphere. The most intriguing result is a detection of a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 98±26 parts-per-million per Kelvin, over the entire temperature range in the sample (800K to 2500K). No existing model predicts this trend over such a large range of temperature. This may be due to a structural difference in the atmospheric temperature profile between the real planetary atmospheres as compared to models.
ContributorsGarhart, Emily (Author) / Christensen, Phil (Thesis advisor) / Line, Michael (Committee member) / Shim, Dan (Committee member) / Arizona State University (Publisher)
Created2019