Connecting the Dots: Investigating Planet Formation and Composition Through Observations of Carbon and Oxygen Species in Stars, Disks, and Planets

Persistent Link:
http://hdl.handle.net/10150/318831
Title:
Connecting the Dots: Investigating Planet Formation and Composition Through Observations of Carbon and Oxygen Species in Stars, Disks, and Planets
Author:
Teske, Johanna Kavanagh
Issue Date:
2014
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
What physical processes and sources of material contribute to exoplanet compositions? Specifically, what roles do the protoplanetary disk composition and structure, and host star abundances play in the different stages of planet formation? In this thesis, beginning with a brief literature review in Chapter 2, I trace oxygen and carbon species through these stages to inform how, when, and where planets form. In Chapter 3 I describe a study of the molecular emission from the warm inner disks of T Tauri stars, where terrestrial planets likely form. I report moderate correlations between HCN emission strength and both stellar accretion rate (measured from UV or optical excess emission associated with accretion) and X-ray luminosity. These correlations point towards accretion related processes being an important source of disk atmosphere heating, and suggests that efficient H₂O formation and/or UV dissociation of N₂ (both also associated with higher stellar accretion rates) may aid in the production of HCN. Studies following mine have further connected the abundance of HCN versus H₂O to the growth and migration of planetesimals in the disk, which helps control the formation of both giant and terrestrial planets. I shift to an already-formed exoplanet in Chapter 4, where I present optical photometry of the best-observed transiting super-Earth GJ 1214b with the goal of constraining the short-wavelength slope of its transmission spectrum. Most previous observations suggested a flat spectrum from the near-IR to the optical, corresponding to a low-scale-height, high-molecular-weight atmosphere. My observations are in general agreement with these findings, keeping the "door open" for a H₂O-rich atmosphere for GJ 1214b, which other published g-band observations appeared to contradict. Chapters 5-7 of my thesis focus on measuring stellar abundances, particularly C/O ratios, in transiting (mostly) hot Jupiter exoplanet host stars from high resolution optical spectroscopy. Host star abundances may indicate the precursor materials present in the disk and available for incorporation into planets. In hot Jupiters, the C/O ratio affects the partitioning of C in the major observable molecules, making C and O diagnostic of temperature structure and composition. I also demonstrate that extra caution is necessary in deriving carbon and oxygen abundances, especially for cool and metal-rich stars. Though exoplanetary C/O ratios are still uncertain, the more precise abundance analysis possible right now for their host stars can help constrain their formation environments and current compositions. I summarize my graduate school research in Chapter 8, and discuss the next steps I will take in my postdoctoral career.
Type:
text; Electronic Dissertation
Keywords:
Astronomy
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Astronomy
Degree Grantor:
University of Arizona
Advisor:
Griffith, Caitlin A.; Najita, Joan; Rieke, George; Schuler, Simon; Cunha, Katia

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleConnecting the Dots: Investigating Planet Formation and Composition Through Observations of Carbon and Oxygen Species in Stars, Disks, and Planetsen_US
dc.creatorTeske, Johanna Kavanaghen_US
dc.contributor.authorTeske, Johanna Kavanaghen_US
dc.date.issued2014-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractWhat physical processes and sources of material contribute to exoplanet compositions? Specifically, what roles do the protoplanetary disk composition and structure, and host star abundances play in the different stages of planet formation? In this thesis, beginning with a brief literature review in Chapter 2, I trace oxygen and carbon species through these stages to inform how, when, and where planets form. In Chapter 3 I describe a study of the molecular emission from the warm inner disks of T Tauri stars, where terrestrial planets likely form. I report moderate correlations between HCN emission strength and both stellar accretion rate (measured from UV or optical excess emission associated with accretion) and X-ray luminosity. These correlations point towards accretion related processes being an important source of disk atmosphere heating, and suggests that efficient H₂O formation and/or UV dissociation of N₂ (both also associated with higher stellar accretion rates) may aid in the production of HCN. Studies following mine have further connected the abundance of HCN versus H₂O to the growth and migration of planetesimals in the disk, which helps control the formation of both giant and terrestrial planets. I shift to an already-formed exoplanet in Chapter 4, where I present optical photometry of the best-observed transiting super-Earth GJ 1214b with the goal of constraining the short-wavelength slope of its transmission spectrum. Most previous observations suggested a flat spectrum from the near-IR to the optical, corresponding to a low-scale-height, high-molecular-weight atmosphere. My observations are in general agreement with these findings, keeping the "door open" for a H₂O-rich atmosphere for GJ 1214b, which other published g-band observations appeared to contradict. Chapters 5-7 of my thesis focus on measuring stellar abundances, particularly C/O ratios, in transiting (mostly) hot Jupiter exoplanet host stars from high resolution optical spectroscopy. Host star abundances may indicate the precursor materials present in the disk and available for incorporation into planets. In hot Jupiters, the C/O ratio affects the partitioning of C in the major observable molecules, making C and O diagnostic of temperature structure and composition. I also demonstrate that extra caution is necessary in deriving carbon and oxygen abundances, especially for cool and metal-rich stars. Though exoplanetary C/O ratios are still uncertain, the more precise abundance analysis possible right now for their host stars can help constrain their formation environments and current compositions. I summarize my graduate school research in Chapter 8, and discuss the next steps I will take in my postdoctoral career.en_US
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectAstronomyen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorGriffith, Caitlin A.en_US
dc.contributor.advisorNajita, Joanen_US
dc.contributor.advisorRieke, Georgeen_US
dc.contributor.advisorSchuler, Simonen_US
dc.contributor.advisorCunha, Katiaen_US
dc.contributor.committeememberGriffith, Caitlin A.en_US
dc.contributor.committeememberRieke, Georgeen_US
dc.contributor.committeememberCunha, Katiaen_US
dc.contributor.committeememberSchuler, Simonen_US
dc.contributor.committeememberApai, Danielen_US
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