First Demonstration of Kernel Phase Interferometry on JWST/MIRI: Prospects for Future Planet Searches Around Post Main Sequence Stars

Abstract: Kernel phase interferometry (KPI) is a post-processing technique that treats a conventional telescope as an interferometer by accurately modeling a telescope pupil as an array of virtual subapertures. KPI provides angular resolution within the diffraction limit by eliminating instrumental phase errors to first order. It has been successfully demonstrated to boost angular resolution on both space- and ground-based observatories, and is especially useful for enhancing space telescopes, as their diameters are smaller than the largest ground-based facilities. Here we present the first demonstration of KPI on JWST/MIRI data at 7.7 microns, 10 microns, and 15 microns. We generate contrast curves for 16 white dwarfs from the MIRI Exoplanets Orbiting White dwarfs (MEOW) Survey, finding significantly deeper contrast at small angular separations compared to traditional imaging with JWST/MIRI, down to within $\lambda$/D. Additionally, we use our KPI setup to successfully recover four known companions orbiting white dwarfs and brown dwarfs. This analysis shows that at these wavelengths KPI can uniquely access the orbital parameter space where inward-migrating post-main-sequence giant exoplanets are now thought to exist. We discuss the prospects for applying KPI to a larger sample of white dwarfs observed with JWST, increasing the volume of directly imaged close-in post-main-sequence exoplanets.