2026-07-09 マックス・プランク研究所
＜関連情報＞
- https://www.mpg.de/26857046/young-giant-gas-planet-beta-pic-b-refuses-to-reveal-its-origin
- https://www.aanda.org/articles/aa/full_html/2026/07/aa60275-26/aa60275-26.html
13COとGRAVITY+によるβ Pictoris bの潜在的な変動性 13CO and potential variability in β Pictoris b with GRAVITY+
A. von Stauffenberg, J. Sauter, P. Mollière, M. Ravet, D. Trevascus, W. Brandner, A. Berdeu, M. Bonnefoy, G. Bourdarot, J.-B. Le Bouquin, G. Chauvin, F. Eisenhauer, M. Houllé, L. Kreidberg, E. Matthews, F. Millour, J. Scigliuto, J. Wang, J. W. Xuan, Y. Zhang and GRAVITY + Collaboration
Astronomy & Astrophysics Published:09 July 2026
DOI:https://doi.org/10.1051/0004-6361/202660275
Abstract
The 12CO/13CO ratio was introduced as an indicator for where in the disk a planet has formed. Previously, a lower value compared to that of the host star was suggested to indicate that a planet accreted CO ice beyond the disk’s CO ice line. In this Letter, we aim to determine the 12CO/13CO value of the directly imaged planet β Pictoris b and whether we can link it to its formation. Its apparent brightness results in an exceptional signal-to-noise ratio of up to ∼60 per wavelength point. We present the first science observations with the upgraded GRAVITY+ instrument at a spectral resolution of R ≈ 4000, which we analysed with petitRADTRANS. Our retrievals robustly indicate 13CO with a 12CO/13CO ratio of 91+24−17, consistent with both a solar to interstellar-medium-like value. Our 12CO/13CO value corroborates recent interpretations that 13CO may be a less useful tracer of formation location in the disk than previously thought; nonetheless, we discuss theories with which this value is consistent. As our observations span ≈7 hours, this enabled us to search for atmospheric variability in β Pictoris b; we report a tentative constraint on the variability amplitude of about 1.4+0.6−0.7%.
