Commissioning Fizeau Interferometry with the Large Binocular Telescope Interferometer

Abstract

This work demonstrates the use of two different observing modes with the twin apertures of the LBT. One pointing mode involves the incoherent juxtaposition of two filled-aperture PSFs to perform differential photometry in the thermal infrared. This is "wall-eyed" pointing, which is used to perform differential photometry on three sets of test targets. To test the possibility of applying this to the study of atmospheres of low-mass objects, one of the targets involves an exoplanet transit in front of its host star, and another involves a secondary occultation. Though the photometric precision in differential mode is increased compared to single-aperture mode, it remains limited by line-of-sight systematics possibly stemming from water vapor variations. The remainder (and majority) of the thesis involves the long-anticipated Fizeau mode---the coherent and multiaxial combination of the LBT beams. Compared to a single filled aperture, the Fizeau mode can generate a PSF that can in principle increase the resolution by a factor of ~3 along the long baseline. A number of technical challenges are described, and a science dataset of a nearby star in Fizeau mode is reduced in a first-ever trial of this mode to perform high-contrast imaging. The PSF remains unstable, particularly in phase. A new codebase was written to perform the requisite angular differential imaging of a Fizeau PSF with highly time-dependent optical aberrations. I describe the results of this process and outline avenues of possible future work.