A Search for Wide-orbit Planets Around M-dwarfs using Deep MIRI 15-micron Images

TL;DR

This study uses deep 15-micron JWST MIRI images to search for wide-orbit gas giant planets around M-dwarfs, achieving high contrast sensitivity and providing new constraints on their occurrence.

Contribution

First application of archival MIRI time-series imaging data to search for wide-orbit planets around M-dwarfs, demonstrating its effectiveness for such studies.

Findings

Achieved median 5σ contrast of 8.9×10⁻⁴ to 6.2×10⁻³ at 1" separation.

Sensitive to Jupiter-sized planets with ~170 K temperature beyond 35 AU at 12.5 pc.

Cataloged nearby sources and assessed their impact on future observations.

Abstract

Wide-orbit ($>$10 AU) gas giant planets shape the architecture of planetary systems, yet their occurrence rate remains poorly constrained. JWST has obtained the deepest mid-infrared images of nearby stars to date through substantial MIRI time-series observations of transiting planets, providing sensitive probes for wide-orbit companions. Here we leverage 15 micron observations from four programs targeting ten M-dwarf systems to search for such planets. By applying reference differential imaging for precise PSF subtraction, we achieve a median 5$\sigma$ contrast of $8.9 \times 10^{-4} - 6.2 \times 10^{-3}$ (median sensitivity in apparent magnitude of 15.8-16.8 mag) at a separation of 1" and $1.2 -9.1 \times 10^{-4}$ (17.5-19.0 mag) at separations $\gtrsim$3". The sensitivity is converted to planet detection probability for each system as a function of planet mass versus semimajor axis. Assuming solar metallicity and a clear atmosphere, we are sensitive to Jupiter-sized planets with an effective temperature of ${\sim}170$ K at separations beyond 35 AU in systems at 12.5 pc. Additionally, we catalog the nearby sources and estimate their possible impact on future observations assuming they are background sources. Our results demonstrate that archival MIRI time-series imaging data is a powerful window into the population of wide-orbit gas giants around M-dwarfs.