| 研究課題/領域番号 |
22K14092
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| 研究機関 | 大学共同利用機関法人自然科学研究機構(新分野創成センター、アストロバイオロジーセンター、生命創成探究 |
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研究代表者 |
Nugroho Stevanus 大学共同利用機関法人自然科学研究機構(新分野創成センター、アストロバイオロジーセンター、生命創成探究, アストロバイオロジーセンター, 特任研究員 (90925968)
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| 研究期間 (年度) |
2022-04-01 – 2025-03-31
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| キーワード | exoplanet / atmosphere / non-homogeneous / high-resolution / spectroscopy |
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| 研究実績の概要 |
With the new datasets from IRD/Subaru, we confirmed our previously detected OH and atomic species on the day side of WASP-33b. We followed it up by resolving the 2 strongest vibrational bands of OH individually as a first step to searching for NLTE signature. From the same datasets, we found evidence of new detection of other atomic species and a non-homogeneous atmosphere indicated by a much weaker/non-detection of OH before than after the secondary eclipse. We constructed a framework to fit the evolution of the line contrast of the planetary spectrum with time using JAX+GPU and confirmed that the line contrast is much higher after the eclipse.
We found no chemical species signature in the atmosphere of a warm super earth, GJ 486b, and excluding H2/He-dominated or a clear 100% water-vapour atmosphere by using IRD, SPIRou and IGRINS data. This potentially suggests that rocky planets around M-dwarf stars might have lost their atmospheres. Using ESPRESSO and UVES at the VLT, we found consistent relative abundance constraints in the WASP-121b transmission spectra across multiple observations demonstrating our robust technique that can be applied to future analyses.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
The evidence of a non-homogenous atmosphere of WASP-33b has been presented at several domestic and international conferences/workshops, and the paper is in preparation. The paper about resolving OH signal on the day-side of WASP-33b by its vibrational band is still under review in the Astronomical Journal.
One of the challenges is stopping the iterative telluric line removal algorithm without involving the detected signal/injection test which can result in a false-positive conclusion. This is one of the unresolved issues that potentially affect the robustness of the physical constraints using high-resolution spectroscopy. We adopted a method that only takes into account the RMS of the data and the residual signal of the telluric that we want to remove, although it might not fully maximise the detected signal and minimise the noise in the data at the very least it minimises the probability of false-positive detections.
We have implemented a Bayesian approach to analysing high-resolution cross-correlation spectroscopy data using Hamiltonian Monte Carlo+No U-Turn Sampler on GPU using JAX/NUMPYRO. As a result, we can constrain many physical parameters faster and more robustly. This paves the way to a much more complex retrieval to understand the 3D nature of the exoplanet atmospheres.
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| 今後の研究の推進方策 |
By adopting a non-bias method of stopping the iterative telluric removal algorithm, we expect to speed up the next analyses, if no unexpected issues occur. We plan to combine all of the available high-resolution spectroscopy data of WASP-33b to perform a complete census of chemical species and retrieve chemical phase curves. This would significantly increase our understanding of the day-side atmosphere of this planet.
Although now we have a fast and robust GPU-based retrieval framework, the limitation is the memory of the GPU. Calculating line absorptions in a line-by-line on-the-fly fashion takes too much GPU memory making it impossible to use more complex and flexible atmospheric models. Therefore, we also plan to create a JAX-compatible precomputed cross-section radiative transfer module to enable temperature-profile retrieval using GPU-based software to significantly speed up the process. Once we are done with this, we will proceed to the next analysis of the KELT-20b and WASP-189b datasets.
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| 次年度使用額が生じた理由 |
I am planning to submit a paper to Astronomical Journal about the non-homogenous day-side of WASP-33b and present a poster at the Exoclimes VI conference at the University of Exeter, UK; Protostars and Planet VII in Kyoto, Japan; and JpGU 2023 meeting in Chiba, Japan. The remaining budget will be used to upgrade the workstation (e.g., buying more storage, GPU), pay for peer-reviewed journal fees, and possibly attend Extreme Solar System Conference in New Zealand on March 2024.
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