JWST/NIRCam 4-5 \(\mu\)m Imaging of the Giant Planet AF Lep b

• Published in: arXiv.org 2024-08
• Main Authors: Franson, Kyle, Balmer, William O, Bowler, Brendan P, Pueyo, Laurent, Zhou, Yifan, Rickman, Emily, Zhang, Zhoujian, Mukherjee, Sagnick, Pearce, Tim D, Daniella C Bardalez Gagliuffi, Biddle, Lauren I, Brandt, Timothy D, Bowens-Rubin, Rachel, Crepp, Justin R, Davidson, James W, Jr, Faherty, Jacqueline, Ginski, Christian, Horch, Elliott P, Morgan, Marvin, Morley, Caroline V, Perrin, Marshall D, Sanghi, Aniket, Salama, Maissa, Theissen, Christopher A, Tran, Quang H, Wolf, Trevor N
• Format: Article
• Language: English
• Subjects: Atmospheric chemistry; Coronagraphs; Imaging; James Webb Space Telescope; Jupiter; Metallicity; Photometry; Planets; Separation
• ISSN: 2331-8422

With a dynamical mass of \(3 \, M_\mathrm{Jup}\), the recently discovered giant planet AF Lep b is the lowest-mass imaged planet with a direct mass measurement. Its youth and spectral type near the L/T transition make it a promising target to study the impact of clouds and atmospheric chemistry at low surface gravities. In this work, we present JWST/NIRCam imaging of AF Lep b. Across two epochs, we detect AF Lep b in F444W (\(4.4 \, \mathrm{\mu m}\)) with S/N ratios of \(9.6\) and \(8.7\), respectively. At the planet's separation of \(320 \, \mathrm{mas}\) during the observations, the coronagraphic throughput is \({\approx}7\%\), demonstrating that NIRCam's excellent sensitivity persists down to small separations. The F444W photometry of AF Lep b affirms the presence of disequilibrium carbon chemistry and enhanced atmospheric metallicity. These observations also place deep limits on wider-separation planets in the system, ruling out \(1.1 \, M_\mathrm{Jup}\) planets beyond \(15.6 \, \mathrm{au}\) (\(0.58\) arcsec), \(1.1 \, M_\mathrm{Sat}\) planets beyond \(27 \, \mathrm{au}\) (\(1\) arcsec), and \(2.8 \, M_\mathrm{Nep}\) planets beyond \(67 \, \mathrm{au}\) (\(2.5\) arcsec). We also present new Keck/NIRC2 \(L'\) imaging of AF Lep b; combining this with the two epochs of F444W photometry and previous Keck \(L'\) photometry provides limits on the long-term \(3{-}5 \, \mathrm{\mu m}\) variability of AF Lep b on months-to-years timescales. AF Lep b is the closest-separation planet imaged with JWST to date, demonstrating that planets can be recovered well inside the nominal (50\% throughput) NIRCam coronagraph inner working angle.