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

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

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 gra...

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Main Authors: 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
Format: Article
Language:English
Published: IOP Publishing 2024-01-01
Series:The Astrophysical Journal Letters
Subjects:
Extrasolar gaseous giant planets
Direct imaging
James Webb Space Telescope
Exoplanet atmospheres
Online Access:https://doi.org/10.3847/2041-8213/ad736a
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Summary: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.
ISSN:2041-8205

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