Characterizing Properties of Optical Fibers and Fiber Couplings to Near-Infrared High-Resolution Spectrographs Critical to Precision Radial-Velocity Studies
Open Access
Author:
McCoy, Keegan Sean
Area of Honors:
Interdisciplinary in Astronomy and Astrophysics and Electrical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Lawrence William Ramsey, Thesis Supervisor Dr. Timothy Joseph Kane, Thesis Honors Advisor Jane Camilla Charlton, Thesis Honors Advisor
The search for exoplanets, planets orbiting stars beyond our own Solar System, is one of the fastest-growing and most exciting areas of astronomical research. Pathfinder, the Penn State Astronomy and Astrophysics Department's fiber-fed, near-infrared (NIR) spectrograph, is designed to explore the technical issues that must be resolved in order to measure precise radial velocities of M dwarfs from ground-based observations at the Hobby-Eberly Telescope. These stellar radial velocities are induced in host stars, such as M dwarfs, by the gravitational interaction with exoplanets. Pathfinder already has demonstrated <10 m/s short-term radial-velocity precision in the NIR, but this thesis investigates the visible and NIR properties of the optical fibers that couple light from the telescope to Pathfinder to achieve even higher precision. Since the stability of a spectrograph's instrument profile is crucial to accurately measure stellar radial velocities, a series of tests were performed on fused-silica, multimode fibers to measure and mitigate modal noise, the time variation of an optical fiber's modal power distribution. The lessons learned from this research and the Pathfinder prototype will be used in the Habitable Zone Planet Finder (HPF), which is a future facility-class, high-resolution NIR spectrograph that will be capable of high-precision (<5 m/s) radial-velocity measurements of Earth-mass planets orbiting mid- to late-type M dwarfs.
