2024-10-09 テキサス大学オースチン校(UT Austin)
＜関連情報＞
- https://news.utexas.edu/2024/10/09/ut-astronomers-race-to-capture-image-of-exoplanet-near-star/
- https://iopscience.iop.org/article/10.3847/2041-8213/ad736a
JWST/NIRCamによる巨大惑星AF Lep bの4～5μm撮像 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 (张周健), Sagnick Mukherjee, Tim D. Pearce, Daniella C. Bardalez Gagliuffi
The Astrophysical Journal Letters Published: 2024 October 4
DOI:10.3847/2041-8213/ad736a
Abstract
With a dynamical mass of 3 MJup, 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 μm) 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 MJup planets beyond 15.6 au (0
58), 1.1 MSat planets beyond 27 au (1”), and 2.8 MNep planets beyond 67 au (25). We also present new Keck/NIRC2L′ 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 μm 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.
