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- All Subjects: Astronomy
- Creators: Department of Physics
Debris disks are a collection of dust grains and planetesimals around a star and are thought to contain the remnants of planet formation. Directly imaging debris disks and studying their morphologies is valuable for studying the planet formation process. In some stellar systems that have a directly imaged debris disk, there are also directly imaged planets. Debris disk structures like gaps and asymmetries can show the gravitational e↵ects of planets that are below the brightness threshold for being detected via direct imaging. We investigate a sample of debris disks in Scorpius-Centaurus (Sco-Cen) that were imaged with the Gemini Planet Imager (GPI), which is an adaptive optics system with a coronagraph to block starlight. We look at two GPI data sets, the GPIES campaign Sco-Cen targets, and a follow-up observing program for Sco-Cen targets. We resolve 5 debris disks in the follow-up program and 13 from the GPIES campaign. By calculating contrast curves, we determine the planet detection limit in each of the GPI images. We find that we could have detected 5 Jupiter mass planets at angular separations greater than about 0.6 arcseconds in our GPIES campaign images. In three of our images we could have detected 2 Jupiter mass planets in wide orbits, but 2 Jupiter masses below the detection limit in our other images. We identify one point source around HD 108904 as a sub-stellar companion candidate. To further check for evidence of planets that are below the detection limit, we measure the surface brightness profile of the disks to check for asymmetries in brightness. We find that one of the edge-on disks has an asymmetric surface brightness profile, HD 106906, and three other edge-on disks have symmetric surface brightness profiles. We also find that two disks, HD 106906 and HD 111520, are asymmetric in radial extent, which is possibly evidence for gravitational interactions with planets.
As the search for life in our universe grows, it is important to not only locate planets outside of our solar system, but also to work towards the ability to understand and characterize their nature. Many current research endeavors focus on the discovery of exoplanets throughout the surrounding universe; however, we still know very little about the characteristics of these exoplanets themselves, particularly their atmospheres. Observatories, such as the Hubble Space Telescope and the Spitzer Space Telescope, have made some of the first observations which revealed information about the atmospheres of exoplanets but have yet to acquire complete and detailed characterizations of exoplanet atmospheres. The EXoplanet Climate Infrared TElescope (EXCITE) is a mission specifically designed to target key information about the atmospheres of exoplanets - including the global and spatially resolved energy budget, chemical bulk-compositions, vertical temperature profiles and circulation patterns across the surface, energy distribution efficiency as a function of equilibrium temperatures, and cloud formation and distribution - in order to generate dynamic and detailed atmospheric characterizations. EXCITE will use phase-resolved transit spectroscopy in the 1-4 micron wavelength range to accomplish these science goals, so it is important that the EXCITE spectrograph system is designed and tested to meet these observational requirements. For my thesis, I present my research on the EXCITE mission science goals and the design of the EXCITE spectrograph system to meet these goals, along with the work I have done in the beginning stages of testing the EXCITE spectrograph system in the lab. The primary result of my research work is the preparation of a simple optics setup in the lab to prepare a laser light source for use in the EXCITE spectrograph system - comparable to the preparation of incoming light by the EXCITE telescope system - which successfully yields an F# = 12.9 and a spot size of s = 39 ± 7 microns. These results meet the expectations of the system and convey appropriate preparation of a light source to begin the assembly and testing of the EXCITE spectrograph optics in the lab.
mining large datasets for transient phenomena. The evolution of massive stars and
compact objects can be studied over cosmic time by identifying supernovae (SNe) and
gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling
GRBs and their afterglows to probe the jets of GRBs can shed light on the emission
mechanism, rate, and energetics of these events.
In Chapter 1, I discuss the current state of astronomical transient study, including
sources of interest, instrumentation, and data reduction techniques, with a focus
on work in the infrared. In Chapter 2, I present original work published in the
Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared
detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of
this work include observing the exoplanet transit of HD189773B, and detecting the
nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope
at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical
Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al.
2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence
for a bright-edged jet. In Chapter 4, I present a look back at previous years of
RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on
the efficiency of following up GRBs detected by the Fermi Space Telescope, before
some final remarks and brief discussion of future work in Chapter 5.
