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- Genre: Masters Thesis
Description
A significant portion of stars occur as binary systems, in which two stellar components orbit a common center of mass. As the number of known exoplanet systems continues to grow, some binary systems are now known to harbor planets around one or both stellar components. As a first look into composition of these planetary systems, I investigate the chemical compositions of 4 binary star systems, each of which is known to contain at least one planet. Stars are known to vary significantly in their composition, and their overall metallicity (represented by iron abundance, [Fe/H]) has been shown to correlate with the likelihood of hosting a planetary system. Furthermore, the detailed chemical composition of a system can give insight into the possible properties of the system's known exoplanets. Using high-resolution spectra, I quantify the abundances of up to 28 elements in each stellar component of the binary systems 16 Cyg, 83 Leo, HD 109749, and HD 195019. A direct comparison is made between each star and its binary companion to give a differential composition for each system. For each star, a comparison of elemental abundance vs. condensation temperature is made, which may be a good diagnostic of refractory-rich terrestrial planets in a system. The elemental ratios C/O and Mg/Si, crucial in determining the atmospheric composition and mineralogy of planets, are calculated and discussed for each star. Finally, the compositions and diagnostics of each binary system are discussed in terms of the known planetary and stellar parameters for each system.
ContributorsCarande, Bryce (Author) / Young, Patrick (Thesis advisor) / Patience, Jennifer L (Thesis advisor) / Anbar, Ariel D (Committee member) / Arizona State University (Publisher)
Created2013
Description
The isotopic compositions of meteorites provide valuable insights into the earliest history of the Solar System and, in some cases, provide constraints on presolar components that contributed to the solar nebula. In the past decade or so, mass-independent isotope anomalies in titanium have become particularly important geochemical tracers to study the distinct isotopic reservoirs in the early Solar System. In particular, mass-independent anomalies in the most neutron-rich isotope of titanium (50Ti) have been used to distinguish between carbonaceous chondritic (CC) and non-carbonaceous chondritic (NC) materials. These two groupings likely represent distinct isotopic reservoirs in the inner (NC) and outer (CC) Solar System. However, while the titanium isotope compositions of CC and NC materials are distinct, each group's full range of compositional variability is poorly characterized. For example, only one CK carbonaceous chondrite group member has been analyzed thus far for its bulk Ti isotope composition. This work aims to characterize better the range of mass-independent Ti isotope compositions within and among the carbonaceous chondrites, which has implications for the degree and potential sources of Ti isotope heterogeneity in the early Solar System. Methods utilized in this study include column chromatography to purify Ti and high-precision multi-collector inductively coupled plasma mass spectrometry for measuring Ti isotope compositions. The Ti isotope compositions of bulk samples of nine carbonaceous chondrites are reported here. In addition, the bulk fractions of the meteorites used in this study were taken from homogenized powders of relatively large (~200 mg each) samples. This was done to assess whether variability in mass-independent Ti isotope compositions previously reported within some meteorites could be a sampling artifact.
Results from this work show that the various CM2 chondrites and ungrouped carbonaceous chondrites have ε50Ti values that are similar, suggesting that the Ti in these samples was likely sourced from a common isotopic reservoir. On the other hand, the ε50Ti values reported for CI1 and CH/CBb bulk samples suggest that the parent bodies of these carbonaceous chondrite groups were formed in isotopic reservoir(s) distinct from that of the other CC groups in the early Solar System.
ContributorsPhelan, Nicole Danielle (Author) / Wadhwa, Meenakshi (Thesis advisor) / Young, Patrick (Committee member) / Nittler, Larry R. (Committee member) / Arizona State University (Publisher)
Created2023
Description
The spectra of brown dwarfs are key to exploring the chemistry and physics thattake place in their atmospheres. Late T dwarf (950 - 500 K) spectra are particularly
diagnostic due to their relatively cloud free atmospheres and deep molecular
bands. With the use of powerful atmospheric retrieval tools, these properties permit
constraints on molecular/atomic abundances and temperature profiles. Building
upon previous analyses on T and Y dwarfs (Line et al. 2017; Zalesky et al. 2019),
I present a uniform retrieval analysis of 50 T dwarfs via their low-resolution near infrared
spectra. This analysis more than doubles the sample of T dwarfs with retrieved
properties. I present updates on current compositional trends and thermal
profile constraints amongst the T dwarf population. My analysis shows that my collection
of objects form trends that are consistent with solar grid model expectations
for water, ammonia, methane, and potassium. I also establish a consistency between
the thermal structures of my objects with those of grid models. Moreover, I explore
the origin of gravity-metallicity discrepancies that are observed in some of my brown
dwarf candidates.
diagnostic due to their relatively cloud free atmospheres and deep molecular
bands. With the use of powerful atmospheric retrieval tools, these properties permit
constraints on molecular/atomic abundances and temperature profiles. Building
upon previous analyses on T and Y dwarfs (Line et al. 2017; Zalesky et al. 2019),
I present a uniform retrieval analysis of 50 T dwarfs via their low-resolution near infrared
spectra. This analysis more than doubles the sample of T dwarfs with retrieved
properties. I present updates on current compositional trends and thermal
profile constraints amongst the T dwarf population. My analysis shows that my collection
of objects form trends that are consistent with solar grid model expectations
for water, ammonia, methane, and potassium. I also establish a consistency between
the thermal structures of my objects with those of grid models. Moreover, I explore
the origin of gravity-metallicity discrepancies that are observed in some of my brown
dwarf candidates.
ContributorsSaboi, Kezman (Author) / Line, Michael R (Thesis advisor) / Patience, Jennifer (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2020