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

Chelsea Adelman, Steph Sallum, Matthew De Furio, Josh Eisner

TL;DR

This study demonstrates kernel phase interferometry (KPI) on JWST/MIRI data, aiming to enhance angular resolution within the diffraction limit to detect close-in exoplanets around post-main-sequence hosts. By modeling the JWST pupil as a dense interferometric array and constructing kernel phases that suppress first-order instrumental errors, the authors generate 5σ contrast curves and attempt companion recoveries using archival MEOW data at 7.7, 10, and 15 μm. They recover four known companions (two brown dwarfs and two white dwarfs) and show KPI can access parameter spaces near $λ/D$ that are challenging for conventional imaging, though uncalibrated KP introduce systematic differences for the closest signals. The results indicate KPI on JWST/MIRI is a viable path to probing inward-migrating post-MS planets and improving population constraints, with calibration and model-parameter optimization expected to further boost sensitivity in future work.

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 $λ$/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.

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

TL;DR

This study demonstrates kernel phase interferometry (KPI) on JWST/MIRI data, aiming to enhance angular resolution within the diffraction limit to detect close-in exoplanets around post-main-sequence hosts. By modeling the JWST pupil as a dense interferometric array and constructing kernel phases that suppress first-order instrumental errors, the authors generate 5σ contrast curves and attempt companion recoveries using archival MEOW data at 7.7, 10, and 15 μm. They recover four known companions (two brown dwarfs and two white dwarfs) and show KPI can access parameter spaces near that are challenging for conventional imaging, though uncalibrated KP introduce systematic differences for the closest signals. The results indicate KPI on JWST/MIRI is a viable path to probing inward-migrating post-MS planets and improving population constraints, with calibration and model-parameter optimization expected to further boost sensitivity in future work.

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 /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.
Paper Structure (8 sections, 3 equations, 5 figures, 1 table)

This paper contains 8 sections, 3 equations, 5 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. Kernel Phase Interferometry
  3. KPI Pupil Model Generation
  4. Observations
  5. Data Reduction
  6. Results
  7. Discussion
  8. Conclusion

Figures (5)

  • Figure 1: Left: A model image of the JWST/MIRI pupil is created. Middle: The pupil image is used to create a model interferometric array. The sub-apertures are regularly spaced and each one with another forms a baseline, which we can use to sample a specific spatial frequency. The colorscale represents the varying transmission $0.70\leq t \leq 1$. Right: The resulting discrete (u,v) coverage from the baselines created between each subaperture in the middle image. The colorscale corresponds to Fourier amplitude, decreasing from the center to the outer edges.
  • Figure 2: Example reduced and Fourier-transformed images, showing a MEOW target, WD 0839-327. Left: The image of the WD which is cropped, bad pixel corrected, and multiplied with a super-Gaussian window to suppress pixels far from the PSF center. Right: The Fourier transform is taken and sampled at a grid of regularly-spaced uv coordinates, where phases are extracted and then projected into KPs.
  • Figure 3: Solid curves show $5\sigma$ contrast limits for 16 WDs in the MEOW dataset. The top x-axis shows the orbital separation at 12 pc, the average distance of the 16 WDs, and the bottom x-axis shows the angular separation in mas. The dashed vertical maroon line shows $\lambda/\mathrm{D}$ for 7.7 $\mu$m.
  • Figure 4: Each panel shows one MIRI image of each target with a known, directly-imaged companion. The top two panels are BDs with known companions, W0146 and W1711, and the bottom two panels are WDs, WD 1202-232 and WD 2105-82, with known companions. The black and yellow dots represent the published separations and position angles of the companions as measured by direct imaging, and the red dots indicate the KPI companion parameters. For three of the four targets the KPI and DI fits' error bars overlap, and for W0146 there are larger systematic offsets. We discuss these results in Sections \ref{['sec:results']} and \ref{['sec:disc']}.
  • Figure 5: The observed KPs are plotted against the model KPs for the best binary fit to the four objects with known companion signals. The top two panels correspond to the two BDs, W0146 and W1711, and the bottom two panels correspond to the two WDs, WD1202-232 and WD2105-82. If a companion signal were present, the data would fall along the dashed black line, indicating a good fit and a one-to-one correlation. The data in the upper right and lower left panels show a strong correlation with the best-fit binary model, and the upper left and lower right show a weaker correlation. These weaker correlations may be due to higher order systematic errors that have not been removed since the KP data are uncalibrated (Sections \ref{['sec:results']} and \ref{['sec:disc']}).