The Astrophysical Journal Letters (Jan 2024)

JWST/NIRCam 4–5 μm Imaging of the Giant Planet AF Lep b

  • Kyle Franson,
  • William O. Balmer,
  • Brendan P. Bowler,
  • Laurent Pueyo,
  • Yifan Zhou,
  • Emily Rickman,
  • Zhoujian Zhang,
  • Sagnick Mukherjee,
  • Tim D. Pearce,
  • Daniella C. Bardalez Gagliuffi,
  • Lauren I. Biddle,
  • Timothy D. Brandt,
  • Rachel Bowens-Rubin,
  • Justin R. Crepp,
  • James W. Davidson Jr.,
  • Jacqueline Faherty,
  • Christian Ginski,
  • Elliott P. Horch,
  • Marvin Morgan,
  • Caroline V. Morley,
  • Marshall D. Perrin,
  • Aniket Sanghi,
  • Maïssa Salama,
  • Christopher A. Theissen,
  • Quang H. Tran,
  • Trevor N. Wolf

DOI
https://doi.org/10.3847/2041-8213/ad736a
Journal volume & issue
Vol. 974, no. 1
p. L11

Abstract

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With a dynamical mass of 3 M _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 μ m) with signal-to-noise ratios of 9.6 and 8.7, respectively. At the planet’s separation of 320 mas during the observations, the coronagraphic throughput is ≈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 _Jup planets beyond 15.6 au (0.″58), 1.1 M _Sat planets beyond 27 au (1″), and 2.8 M _Nep planets beyond 67 au (2.″5). We also present new Keck/NIRC2 $L^{\prime} $ imaging of AF Lep b; combining this with the two epochs of F444W photometry and previous Keck $L^{\prime} $ photometry provides limits on the long-term 3–5 μ m variability of AF Lep b on timescales of months to years. 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.

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