ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- All Subjects: Astrophysics
- Creators: Simon, Molly
Description
This thesis presents the results of a brown dwarf companion direct imaging survey. Over a total of 4 nights, 200 B and A stars were imaged using the Keck telescope and the Near Infrared Camera 2 (NIRC2). Presented here are preliminary results from the nights of 04 June 2014 and 17 December 2013. Brown dwarfs are partially degenerate objects that have masses between approximately 13 MJup and 75 MJup. Currently, the number of brown dwarf companions found around high mass stars is small. Finding brown dwarfs as companions to B and A stars will allow astronomers to study these objects when they are young and bright, giving key insights into their formation and evolution.
\par A pipeline was written specifically for these data sets that includes dark subtraction, flat field correction, bad pixel correction, distortion correction, centering, filtering, and point spread function (PSF) subtraction. This subtraction was accomplished using the Karhunen-Loeve Image Processing (KLIP) algorithm which employs principal component analysis and Karhunen-Loeve (KL) transforms to subtract out starlight and artifacts from the images and allow for easier detection of a candidate companion.
\par Only candidate companions from the night of 04 June 2014 were analyzed, with 95 candidate companions found around 22 stars. Due to a lack of some necessary images, 91 companions around 20 stars were analyzed and their masses were found to be approximately 6 MJup to 150 MJup with projected separations from the host star of approximately 100AU to 900AU. An upper limit of 6.6% was placed on stellar companion frequency and an upper limit of 93% was placed on brown dwarf companion frequency. This survey achieved a median sensitivity of ΔK of 12.6 at 1" and a ΔK of 15.1 at 3.6". Further observations will be required to determine whether the candidates found are true co-moving companions or background stars not bound to the host star.
ContributorsGarani, Jasmine (Author) / Patience, Jennifer (Thesis advisor) / Simon, Molly (Committee member) / Line, Michael (Committee member) / Nielsen, Eric (Committee member) / Arizona State University (Publisher)
Created2022
Description
Direct imaging is a powerful tool in revealing the architectures of young planetary systems, clearly showing the structure of circumstellar disks. Circumstellar disks, similar to the asteroid belt, are critical elements of any planetary system, and the study of them is important to understanding planet formation. Disks around several main sequence stars have already been observed directly interacting with exoplanets in their respective systems. Imaging can help answer many of the key questions of how disks interact in their respective systems. The Gemini Planet Imager is a high contrast imaging instrument that has spatially resolved several circumstellar disks for the first time, many exhibiting tracers of ongoing planet formation or the presence of a perturbing exoplanet. With this new sample, population analyses of characteristics of disks can now be explored and compared to information at other wavelengths. Direct imaging is also a uniquely accessible tool in engaging students and the community in astronomy. In combination with a course-based undergraduate research experience, direct imaging has the ability to engage students in the process of doing research in a very accessible manner. In Chapter 1, I introduce the concepts related to circumstellar debris disks, further focusing on the sub-field of direct imaging and its value in understanding these systems and engaging students in astronomy. In Chapter 2, I present four images of newly-resolved debris disks in the Scorpius-Centaurus association, comparing their characteristics with many other spatially-resolved circumstellar disks within the moving group. In Chapter 3, I present a uniform analysis of debris disk structure using a consistent and empirically-informed modeling approach. In Chapter 4, I present my findings and experiences in developing and teaching a course-based undergraduate research experience for students in the country’s first online astronomy degree program centered on the direct imaging of brown dwarfs. In Chapter 5, I present my conclusions on the topics I have investigated and discuss future work within the field of direct imaging and its role in driving astronomy research and education forward.
ContributorsHom, Justin (Author) / Patience, Jennifer (Thesis advisor) / Knierman, Karen (Committee member) / Scowen, Paul (Committee member) / Simon, Molly (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2023