Dyn-Atmo巡天：动力学基准天体GJ 758 B的JWST/NIRSpec光谱观测
The Dyn-Atmo Survey: JWST/NIRSpec spectroscopy of dynamical benchmark GJ 758 B
- Space Telescope Science Institute（太空望远镜科学研究所）
- European Space Agency (ESA)（欧洲空间局）
- Amherst College（阿默斯特学院）
- American Museum of Natural History（美国自然历史博物馆）
- University of Texas at Austin（德克萨斯大学奥斯汀分校）
- Smith College（史密斯学院）
- Northwestern University（西北大学）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
通过JWST/NIRSpec光谱观测褐矮星伴星GJ 758 B，结合动力学质量基准，发现大气模型简并性导致推断偏差，提出含云层及分子丰度调整的最佳拟合模型。
中文摘要 AI 辅助
我们展示了褐矮星伴星GJ 758 B的新JWST/NIRSpec IFU高对比度光谱观测。对主星的广泛视向速度监测，通过表征其联合轨道动力学，实现了对伴星质量的高精度测量。先前的空间和地面光度测量与光谱观测相结合，加上与光谱模型无关的质量，使该目标成为校准具有已知质量-年龄-光度简并性的演化模型的理想基准。对NIRSpec/IFU数据（F290LP,G395H；λ∈[2.87-5.27] μm）的模板匹配分析以极高的显著性（265.2σ）在预期轨道位置探测到该伴星。包括已发表数据集在内的多种不同光谱模型族的综合光谱分析表明，使用均匀半径先验的推断受到不准确后验的困扰。金属丰度、重力和云层之间的大气模型简并性将所有测试模型族的推断质量/重力/半径拉向参数空间的非物理区域。使用质量上的高斯先验进行约束推断可以缓解此问题，但无云模型仍难以准确再现K波段光度，并导致与动力学不一致的质量推断。我们探索了使用自定义后处理云层以及氨和硫化氢分子丰度扰动来修改光谱模型。我们发现最佳拟合模型包括无斑块（孔洞分数f_hole = 0）的云层、氨的少量丰度减少和硫化氢的中等增强。
英文摘要
We present new JWST/NIRSpec IFU high contrast spectroscopic observations of the brown dwarf companion GJ 758 B. Extensive radial velocity monitoring of the primary has enabled high-precision measurements of the companion mass through characterization of their joint orbital dynamics. The combination of prior space- and ground-based photometry and spectroscopic observations in concert with a spectral model-independent mass makes this target an ideal benchmark for calibrating evolutionary models with known mass-age-luminosity degeneracies. A template-matching analysis on the NIRSpec/IFU data (F290LP,G395H; $λ\in$ [2.87-5.27] $μ$m) detects the companion at the expected orbital position with incredible significance (265.2$σ$). Comprehensive spectral analysis including published datasets over a variety of different spectral model families reveal that an inference using a uniform radius prior is plagued by inaccurate posteriors. The atmospheric model degeneracy between metallicity, gravity, and clouds pull the inferred mass/gravity/radius to an unphysical portion of parameter space for all model families tested. A constrained inference with a gaussian prior on the mass can mitigate this issue but models without clouds still struggle to accurately reproduce the K-band photometry and result in mass inferences which are inconsistent with the dynamics. We explore modifying the spectral models with custom post-processed clouds and molecular abundance perturbations of ammonia and hydrogen sulfide. We find the best-fitting model includes clouds with no patchiness (hole fraction f$_\mathrm{hole}$ = 0), a small fractional depletion in ammonia and moderate enhancement in hydrogen sulfide.
